| 1 | .TH LIBPNG 3 "September 10, 2009"
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| 2 | .SH NAME
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| 3 | libpng \- Portable Network Graphics (PNG) Reference Library 1.2.40
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| 4 | .SH SYNOPSIS
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| 5 | \fI\fB
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| 6 |
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| 7 | \fB#include <png.h>\fP
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| 8 |
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| 9 | \fI\fB
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| 10 |
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| 11 | \fBpng_uint_32 png_access_version_number \fI(void\fP\fB);\fP
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| 12 |
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| 13 | \fI\fB
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| 14 |
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| 15 | \fBint png_check_sig (png_bytep \fP\fIsig\fP\fB, int \fInum\fP\fB);\fP
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| 16 |
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| 17 | \fI\fB
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| 18 |
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| 19 | \fBvoid png_chunk_error (png_structp \fP\fIpng_ptr\fP\fB, png_const_charp \fIerror\fP\fB);\fP
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| 20 |
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| 21 | \fI\fB
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| 22 |
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| 23 | \fBvoid png_chunk_warning (png_structp \fP\fIpng_ptr\fP\fB, png_const_charp \fImessage\fP\fB);\fP
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| 24 |
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| 25 | \fI\fB
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| 26 |
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| 27 | \fBvoid png_convert_from_struct_tm (png_timep \fP\fIptime\fP\fB, struct tm FAR * \fIttime\fP\fB);\fP
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| 28 |
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| 29 | \fI\fB
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| 30 |
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| 31 | \fBvoid png_convert_from_time_t (png_timep \fP\fIptime\fP\fB, time_t \fIttime\fP\fB);\fP
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| 32 |
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| 33 | \fI\fB
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| 34 |
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| 35 | \fBpng_charp png_convert_to_rfc1123 (png_structp \fP\fIpng_ptr\fP\fB, png_timep \fIptime\fP\fB);\fP
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| 36 |
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| 37 | \fI\fB
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| 38 |
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| 39 | \fBpng_infop png_create_info_struct (png_structp \fIpng_ptr\fP\fB);\fP
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| 40 |
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| 41 | \fI\fB
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| 42 |
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| 43 | \fBpng_structp png_create_read_struct (png_const_charp \fP\fIuser_png_ver\fP\fB, png_voidp \fP\fIerror_ptr\fP\fB, png_error_ptr \fP\fIerror_fn\fP\fB, png_error_ptr \fIwarn_fn\fP\fB);\fP
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| 44 |
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| 45 | \fI\fB
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| 46 |
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| 47 | \fBpng_structp png_create_read_struct_2(png_const_charp \fP\fIuser_png_ver\fP\fB, png_voidp \fP\fIerror_ptr\fP\fB, png_error_ptr \fP\fIerror_fn\fP\fB, png_error_ptr \fP\fIwarn_fn\fP\fB, png_voidp \fP\fImem_ptr\fP\fB, png_malloc_ptr \fP\fImalloc_fn\fP\fB, png_free_ptr \fIfree_fn\fP\fB);\fP
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| 48 |
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| 49 | \fI\fB
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| 50 |
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| 51 | \fBpng_structp png_create_write_struct (png_const_charp \fP\fIuser_png_ver\fP\fB, png_voidp \fP\fIerror_ptr\fP\fB, png_error_ptr \fP\fIerror_fn\fP\fB, png_error_ptr \fIwarn_fn\fP\fB);\fP
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| 52 |
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| 53 | \fI\fB
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| 54 |
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| 55 | \fBpng_structp png_create_write_struct_2(png_const_charp \fP\fIuser_png_ver\fP\fB, png_voidp \fP\fIerror_ptr\fP\fB, png_error_ptr \fP\fIerror_fn\fP\fB, png_error_ptr \fP\fIwarn_fn\fP\fB, png_voidp \fP\fImem_ptr\fP\fB, png_malloc_ptr \fP\fImalloc_fn\fP\fB, png_free_ptr \fIfree_fn\fP\fB);\fP
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| 56 |
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| 57 | \fI\fB
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| 58 |
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| 59 | \fBint png_debug(int \fP\fIlevel\fP\fB, png_const_charp \fImessage\fP\fB);\fP
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| 60 |
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| 61 | \fI\fB
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| 62 |
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| 63 | \fBint png_debug1(int \fP\fIlevel\fP\fB, png_const_charp \fP\fImessage\fP\fB, \fIp1\fP\fB);\fP
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| 64 |
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| 65 | \fI\fB
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| 66 |
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| 67 | \fBint png_debug2(int \fP\fIlevel\fP\fB, png_const_charp \fP\fImessage\fP\fB, \fP\fIp1\fP\fB, \fIp2\fP\fB);\fP
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| 68 |
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| 69 | \fI\fB
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| 70 |
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| 71 | \fBvoid png_destroy_info_struct (png_structp \fP\fIpng_ptr\fP\fB, png_infopp \fIinfo_ptr_ptr\fP\fB);\fP
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| 72 |
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| 73 | \fI\fB
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| 74 |
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| 75 | \fBvoid png_destroy_read_struct (png_structpp \fP\fIpng_ptr_ptr\fP\fB, png_infopp \fP\fIinfo_ptr_ptr\fP\fB, png_infopp \fIend_info_ptr_ptr\fP\fB);\fP
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| 76 |
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| 77 | \fI\fB
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| 78 |
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| 79 | \fBvoid png_destroy_write_struct (png_structpp \fP\fIpng_ptr_ptr\fP\fB, png_infopp \fIinfo_ptr_ptr\fP\fB);\fP
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| 80 |
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| 81 | \fI\fB
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| 82 |
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| 83 | \fBvoid png_error (png_structp \fP\fIpng_ptr\fP\fB, png_const_charp \fIerror\fP\fB);\fP
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| 84 |
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| 85 | \fI\fB
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| 86 |
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| 87 | \fBvoid png_free (png_structp \fP\fIpng_ptr\fP\fB, png_voidp \fIptr\fP\fB);\fP
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| 88 |
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| 89 | \fI\fB
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| 90 |
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| 91 | \fBvoid png_free_chunk_list (png_structp \fIpng_ptr\fP\fB);\fP
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| 92 |
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| 93 | \fI\fB
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| 94 |
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| 95 | \fBvoid png_free_default(png_structp \fP\fIpng_ptr\fP\fB, png_voidp \fIptr\fP\fB);\fP
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| 96 |
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| 97 | \fI\fB
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| 98 |
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| 99 | \fBvoid png_free_data (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, int \fInum\fP\fB);\fP
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| 100 |
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| 101 | \fI\fB
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| 102 |
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| 103 | \fBpng_byte png_get_bit_depth (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fIinfo_ptr\fP\fB);\fP
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| 104 |
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| 105 | \fI\fB
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| 106 |
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| 107 | \fBpng_uint_32 png_get_bKGD (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, png_color_16p \fI*background\fP\fB);\fP
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| 108 |
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| 109 | \fI\fB
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| 110 |
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| 111 | \fBpng_byte png_get_channels (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fIinfo_ptr\fP\fB);\fP
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| 112 |
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| 113 | \fI\fB
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| 114 |
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| 115 | \fBpng_uint_32 png_get_cHRM (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, double \fP\fI*white_x\fP\fB, double \fP\fI*white_y\fP\fB, double \fP\fI*red_x\fP\fB, double \fP\fI*red_y\fP\fB, double \fP\fI*green_x\fP\fB, double \fP\fI*green_y\fP\fB, double \fP\fI*blue_x\fP\fB, double \fI*blue_y\fP\fB);\fP
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| 116 |
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| 117 | \fI\fB
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| 118 |
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| 119 | \fBpng_uint_32 png_get_cHRM_fixed (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, png_uint_32 \fP\fI*white_x\fP\fB, png_uint_32 \fP\fI*white_y\fP\fB, png_uint_32 \fP\fI*red_x\fP\fB, png_uint_32 \fP\fI*red_y\fP\fB, png_uint_32 \fP\fI*green_x\fP\fB, png_uint_32 \fP\fI*green_y\fP\fB, png_uint_32 \fP\fI*blue_x\fP\fB, png_uint_32 \fI*blue_y\fP\fB);\fP
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| 120 |
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| 121 | \fI\fB
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| 122 |
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| 123 | \fBpng_byte png_get_color_type (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fIinfo_ptr\fP\fB);\fP
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| 124 |
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| 125 | \fI\fB
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| 126 |
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| 127 | \fBpng_byte png_get_compression_type (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fIinfo_ptr\fP\fB);\fP
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| 128 |
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| 129 | \fI\fB
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| 130 |
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| 131 | \fBpng_byte png_get_copyright (png_structp \fIpng_ptr\fP\fB);\fP
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| 132 |
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| 133 | \fI\fB
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| 134 |
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| 135 | \fBpng_voidp png_get_error_ptr (png_structp \fIpng_ptr\fP\fB);\fP
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| 136 |
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| 137 | \fI\fB
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| 138 |
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| 139 | \fBpng_byte png_get_filter_type (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fIinfo_ptr\fP\fB);\fP
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| 140 |
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| 141 | \fI\fB
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| 142 |
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| 143 | \fBpng_uint_32 png_get_gAMA (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, double \fI*file_gamma\fP\fB);\fP
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| 144 |
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| 145 | \fI\fB
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| 146 |
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| 147 | \fBpng_uint_32 png_get_gAMA_fixed (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, png_uint_32 \fI*int_file_gamma\fP\fB);\fP
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| 148 |
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| 149 | \fI\fB
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| 150 |
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| 151 | \fBpng_byte png_get_header_ver (png_structp \fIpng_ptr\fP\fB);\fP
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| 152 |
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| 153 | \fI\fB
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| 154 |
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| 155 | \fBpng_byte png_get_header_version (png_structp \fIpng_ptr\fP\fB);\fP
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| 156 |
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| 157 | \fI\fB
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| 158 |
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| 159 | \fBpng_uint_32 png_get_hIST (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, png_uint_16p \fI*hist\fP\fB);\fP
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| 160 |
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| 161 | \fI\fB
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| 162 |
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| 163 | \fBpng_uint_32 png_get_iCCP (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, png_charpp \fP\fIname\fP\fB, int \fP\fI*compression_type\fP\fB, png_charpp \fP\fIprofile\fP\fB, png_uint_32 \fI*proflen\fP\fB);\fP
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| 164 |
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| 165 | \fI\fB
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| 166 |
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| 167 | \fBpng_uint_32 png_get_IHDR (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, png_uint_32 \fP\fI*width\fP\fB, png_uint_32 \fP\fI*height\fP\fB, int \fP\fI*bit_depth\fP\fB, int \fP\fI*color_type\fP\fB, int \fP\fI*interlace_type\fP\fB, int \fP\fI*compression_type\fP\fB, int \fI*filter_type\fP\fB);\fP
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| 168 |
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| 169 | \fI\fB
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| 170 |
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| 171 | \fBpng_uint_32 png_get_image_height (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fIinfo_ptr\fP\fB);\fP
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| 172 |
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| 173 | \fI\fB
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| 174 |
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| 175 | \fBpng_uint_32 png_get_image_width (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fIinfo_ptr\fP\fB);\fP
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| 176 |
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| 177 | \fI\fB
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| 178 |
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| 179 | \fB#if \fI!defined(PNG_1_0_X)
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| 180 |
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| 181 | \fBpng_int_32 png_get_int_32 (png_bytep \fIbuf\fP\fB);\fP
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| 182 |
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| 183 | \fI\fB#endif
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| 184 |
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| 185 | \fI\fB
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| 186 |
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| 187 | \fBpng_byte png_get_interlace_type (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fIinfo_ptr\fP\fB);\fP
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| 188 |
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| 189 | \fI\fB
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| 190 |
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| 191 | \fBpng_voidp png_get_io_ptr (png_structp \fIpng_ptr\fP\fB);\fP
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| 192 |
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| 193 | \fI\fB
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| 194 |
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| 195 | \fBpng_byte png_get_libpng_ver (png_structp \fIpng_ptr\fP\fB);\fP
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| 196 |
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| 197 | \fI\fB
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| 198 |
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| 199 | \fBpng_voidp png_get_mem_ptr(png_structp \fIpng_ptr\fP\fB);\fP
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| 200 |
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| 201 | \fI\fB
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| 202 |
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| 203 | \fBpng_uint_32 png_get_oFFs (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, png_uint_32 \fP\fI*offset_x\fP\fB, png_uint_32 \fP\fI*offset_y\fP\fB, int \fI*unit_type\fP\fB);\fP
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| 204 |
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| 205 | \fI\fB
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| 206 |
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| 207 | \fBpng_uint_32 png_get_pCAL (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, png_charp \fP\fI*purpose\fP\fB, png_int_32 \fP\fI*X0\fP\fB, png_int_32 \fP\fI*X1\fP\fB, int \fP\fI*type\fP\fB, int \fP\fI*nparams\fP\fB, png_charp \fP\fI*units\fP\fB, png_charpp \fI*params\fP\fB);\fP
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| 208 |
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| 209 | \fI\fB
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| 210 |
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| 211 | \fBpng_uint_32 png_get_pHYs (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, png_uint_32 \fP\fI*res_x\fP\fB, png_uint_32 \fP\fI*res_y\fP\fB, int \fI*unit_type\fP\fB);\fP
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| 212 |
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| 213 | \fI\fB
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| 214 |
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| 215 | \fBfloat png_get_pixel_aspect_ratio (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fIinfo_ptr\fP\fB);\fP
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| 216 |
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| 217 | \fI\fB
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| 218 |
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| 219 | \fBpng_uint_32 png_get_pixels_per_meter (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fIinfo_ptr\fP\fB);\fP
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| 220 |
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| 221 | \fI\fB
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| 222 |
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| 223 | \fBpng_voidp png_get_progressive_ptr (png_structp \fIpng_ptr\fP\fB);\fP
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| 224 |
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| 225 | \fI\fB
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| 226 |
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| 227 | \fBpng_uint_32 png_get_PLTE (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, png_colorp \fP\fI*palette\fP\fB, int \fI*num_palette\fP\fB);\fP
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| 228 |
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| 229 | \fI\fB
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| 230 |
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| 231 | \fBpng_byte png_get_rgb_to_gray_status (png_structp \fIpng_ptr)
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| 232 |
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| 233 | \fBpng_uint_32 png_get_rowbytes (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fIinfo_ptr\fP\fB);\fP
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| 234 |
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| 235 | \fI\fB
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| 236 |
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| 237 | \fBpng_bytepp png_get_rows (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fIinfo_ptr\fP\fB);\fP
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| 238 |
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| 239 | \fI\fB
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| 240 |
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| 241 | \fBpng_uint_32 png_get_sBIT (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, png_color_8p \fI*sig_bit\fP\fB);\fP
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| 242 |
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| 243 | \fI\fB
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| 244 |
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| 245 | \fBpng_bytep png_get_signature (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fIinfo_ptr\fP\fB);\fP
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| 246 |
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| 247 | \fI\fB
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| 248 |
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| 249 | \fBpng_uint_32 png_get_sPLT (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, png_spalette_p \fI*splt_ptr\fP\fB);\fP
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| 250 |
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| 251 | \fI\fB
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| 252 |
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| 253 | \fBpng_uint_32 png_get_sRGB (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, int \fI*intent\fP\fB);\fP
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| 254 |
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| 255 | \fI\fB
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| 256 |
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| 257 | \fBpng_uint_32 png_get_text (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, png_textp \fP\fI*text_ptr\fP\fB, int \fI*num_text\fP\fB);\fP
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| 258 |
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| 259 | \fI\fB
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| 260 |
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| 261 | \fBpng_uint_32 png_get_tIME (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, png_timep \fI*mod_time\fP\fB);\fP
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| 262 |
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| 263 | \fI\fB
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| 264 |
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| 265 | \fBpng_uint_32 png_get_tRNS (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, png_bytep \fP\fI*trans\fP\fB, int \fP\fI*num_trans\fP\fB, png_color_16p \fI*trans_values\fP\fB);\fP
|
|---|
| 266 |
|
|---|
| 267 | \fI\fB
|
|---|
| 268 |
|
|---|
| 269 | \fB#if \fI!defined(PNG_1_0_X)
|
|---|
| 270 |
|
|---|
| 271 | \fBpng_uint_16 png_get_uint_16 (png_bytep \fIbuf\fP\fB);\fP
|
|---|
| 272 |
|
|---|
| 273 | \fI\fB
|
|---|
| 274 |
|
|---|
| 275 | \fBpng_uint_32 png_get_uint_31 (png_bytep \fIbuf\fP\fB);\fP
|
|---|
| 276 |
|
|---|
| 277 | \fI\fB
|
|---|
| 278 |
|
|---|
| 279 | \fBpng_uint_32 png_get_uint_32 (png_bytep \fIbuf\fP\fB);\fP
|
|---|
| 280 |
|
|---|
| 281 | \fI\fB#endif
|
|---|
| 282 |
|
|---|
| 283 | \fI\fB
|
|---|
| 284 |
|
|---|
| 285 | \fBpng_uint_32 png_get_unknown_chunks (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, png_unknown_chunkpp \fIunknowns\fP\fB);\fP
|
|---|
| 286 |
|
|---|
| 287 | \fI\fB
|
|---|
| 288 |
|
|---|
| 289 | \fBpng_voidp png_get_user_chunk_ptr (png_structp \fIpng_ptr\fP\fB);\fP
|
|---|
| 290 |
|
|---|
| 291 | \fI\fB
|
|---|
| 292 |
|
|---|
| 293 | \fBpng_uint_32 png_get_user_height_max( png_structp \fIpng_ptr\fP\fB);\fP
|
|---|
| 294 |
|
|---|
| 295 | \fI\fB
|
|---|
| 296 |
|
|---|
| 297 | \fBpng_voidp png_get_user_transform_ptr (png_structp \fIpng_ptr\fP\fB);\fP
|
|---|
| 298 |
|
|---|
| 299 | \fI\fB
|
|---|
| 300 |
|
|---|
| 301 | \fBpng_uint_32 png_get_user_width_max (png_structp \fIpng_ptr\fP\fB);\fP
|
|---|
| 302 |
|
|---|
| 303 | \fI\fB
|
|---|
| 304 |
|
|---|
| 305 | \fBpng_uint_32 png_get_valid (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, png_uint_32 \fIflag\fP\fB);\fP
|
|---|
| 306 |
|
|---|
| 307 | \fI\fB
|
|---|
| 308 |
|
|---|
| 309 | \fBpng_int_32 png_get_x_offset_microns (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fIinfo_ptr\fP\fB);\fP
|
|---|
| 310 |
|
|---|
| 311 | \fI\fB
|
|---|
| 312 |
|
|---|
| 313 | \fBpng_int_32 png_get_x_offset_pixels (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fIinfo_ptr\fP\fB);\fP
|
|---|
| 314 |
|
|---|
| 315 | \fI\fB
|
|---|
| 316 |
|
|---|
| 317 | \fBpng_uint_32 png_get_x_pixels_per_meter (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fIinfo_ptr\fP\fB);\fP
|
|---|
| 318 |
|
|---|
| 319 | \fI\fB
|
|---|
| 320 |
|
|---|
| 321 | \fBpng_int_32 png_get_y_offset_microns (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fIinfo_ptr\fP\fB);\fP
|
|---|
| 322 |
|
|---|
| 323 | \fI\fB
|
|---|
| 324 |
|
|---|
| 325 | \fBpng_int_32 png_get_y_offset_pixels (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fIinfo_ptr\fP\fB);\fP
|
|---|
| 326 |
|
|---|
| 327 | \fI\fB
|
|---|
| 328 |
|
|---|
| 329 | \fBpng_uint_32 png_get_y_pixels_per_meter (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fIinfo_ptr\fP\fB);\fP
|
|---|
| 330 |
|
|---|
| 331 | \fI\fB
|
|---|
| 332 |
|
|---|
| 333 | \fBpng_uint_32 png_get_compression_buffer_size (png_structp \fIpng_ptr\fP\fB);\fP
|
|---|
| 334 |
|
|---|
| 335 | \fI\fB
|
|---|
| 336 |
|
|---|
| 337 | \fBint png_handle_as_unknown (png_structp \fP\fIpng_ptr\fP\fB, png_bytep \fIchunk_name\fP\fB);\fP
|
|---|
| 338 |
|
|---|
| 339 | \fI\fB
|
|---|
| 340 |
|
|---|
| 341 | \fBvoid png_init_io (png_structp \fP\fIpng_ptr\fP\fB, FILE \fI*fp\fP\fB);\fP
|
|---|
| 342 |
|
|---|
| 343 | \fI\fB
|
|---|
| 344 |
|
|---|
| 345 | \fBDEPRECATED: void png_info_init (png_infop \fIinfo_ptr\fP\fB);\fP
|
|---|
| 346 |
|
|---|
| 347 | \fI\fB
|
|---|
| 348 |
|
|---|
| 349 | \fBDEPRECATED: void png_info_init_2 (png_infopp \fP\fIptr_ptr\fP\fB, png_size_t \fIpng_info_struct_size\fP\fB);\fP
|
|---|
| 350 |
|
|---|
| 351 | \fI\fB
|
|---|
| 352 |
|
|---|
| 353 | \fBpng_voidp png_malloc (png_structp \fP\fIpng_ptr\fP\fB, png_uint_32 \fIsize\fP\fB);\fP
|
|---|
| 354 |
|
|---|
| 355 | \fI\fB
|
|---|
| 356 |
|
|---|
| 357 | \fBpng_voidp png_malloc_default(png_structp \fP\fIpng_ptr\fP\fB, png_uint_32 \fIsize\fP\fB);\fP
|
|---|
| 358 |
|
|---|
| 359 | \fI\fB
|
|---|
| 360 |
|
|---|
| 361 | \fBvoidp png_memcpy (png_voidp \fP\fIs1\fP\fB, png_voidp \fP\fIs2\fP\fB, png_size_t \fIsize\fP\fB);\fP
|
|---|
| 362 |
|
|---|
| 363 | \fI\fB
|
|---|
| 364 |
|
|---|
| 365 | \fBpng_voidp png_memcpy_check (png_structp \fP\fIpng_ptr\fP\fB, png_voidp \fP\fIs1\fP\fB, png_voidp \fP\fIs2\fP\fB, png_uint_32 \fIsize\fP\fB);\fP
|
|---|
| 366 |
|
|---|
| 367 | \fI\fB
|
|---|
| 368 |
|
|---|
| 369 | \fBvoidp png_memset (png_voidp \fP\fIs1\fP\fB, int \fP\fIvalue\fP\fB, png_size_t \fIsize\fP\fB);\fP
|
|---|
| 370 |
|
|---|
| 371 | \fI\fB
|
|---|
| 372 |
|
|---|
| 373 | \fBpng_voidp png_memset_check (png_structp \fP\fIpng_ptr\fP\fB, png_voidp \fP\fIs1\fP\fB, int \fP\fIvalue\fP\fB, png_uint_32 \fIsize\fP\fB);\fP
|
|---|
| 374 |
|
|---|
| 375 | \fI\fB
|
|---|
| 376 |
|
|---|
| 377 | \fBDEPRECATED: void png_permit_empty_plte (png_structp \fP\fIpng_ptr\fP\fB, int \fIempty_plte_permitted\fP\fB);\fP
|
|---|
| 378 |
|
|---|
| 379 | \fI\fB
|
|---|
| 380 |
|
|---|
| 381 | \fBvoid png_process_data (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, png_bytep \fP\fIbuffer\fP\fB, png_size_t \fIbuffer_size\fP\fB);\fP
|
|---|
| 382 |
|
|---|
| 383 | \fI\fB
|
|---|
| 384 |
|
|---|
| 385 | \fBvoid png_progressive_combine_row (png_structp \fP\fIpng_ptr\fP\fB, png_bytep \fP\fIold_row\fP\fB, png_bytep \fInew_row\fP\fB);\fP
|
|---|
| 386 |
|
|---|
| 387 | \fI\fB
|
|---|
| 388 |
|
|---|
| 389 | \fBvoid png_read_destroy (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, png_infop \fIend_info_ptr\fP\fB);\fP
|
|---|
| 390 |
|
|---|
| 391 | \fI\fB
|
|---|
| 392 |
|
|---|
| 393 | \fBvoid png_read_end (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fIinfo_ptr\fP\fB);\fP
|
|---|
| 394 |
|
|---|
| 395 | \fI\fB
|
|---|
| 396 |
|
|---|
| 397 | \fBvoid png_read_image (png_structp \fP\fIpng_ptr\fP\fB, png_bytepp \fIimage\fP\fB);\fP
|
|---|
| 398 |
|
|---|
| 399 | \fI\fB
|
|---|
| 400 |
|
|---|
| 401 | \fBDEPRECATED: void png_read_init (png_structp \fIpng_ptr\fP\fB);\fP
|
|---|
| 402 |
|
|---|
| 403 | \fI\fB
|
|---|
| 404 |
|
|---|
| 405 | \fBDEPRECATED: void png_read_init_2 (png_structpp \fP\fIptr_ptr\fP\fB, png_const_charp \fP\fIuser_png_ver\fP\fB, png_size_t \fP\fIpng_struct_size\fP\fB, png_size_t \fIpng_info_size\fP\fB);\fP
|
|---|
| 406 |
|
|---|
| 407 | \fI\fB
|
|---|
| 408 |
|
|---|
| 409 | \fBvoid png_read_info (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fIinfo_ptr\fP\fB);\fP
|
|---|
| 410 |
|
|---|
| 411 | \fI\fB
|
|---|
| 412 |
|
|---|
| 413 | \fBvoid png_read_png (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, int \fP\fItransforms\fP\fB, png_voidp \fIparams\fP\fB);\fP
|
|---|
| 414 |
|
|---|
| 415 | \fI\fB
|
|---|
| 416 |
|
|---|
| 417 | \fBvoid png_read_row (png_structp \fP\fIpng_ptr\fP\fB, png_bytep \fP\fIrow\fP\fB, png_bytep \fIdisplay_row\fP\fB);\fP
|
|---|
| 418 |
|
|---|
| 419 | \fI\fB
|
|---|
| 420 |
|
|---|
| 421 | \fBvoid png_read_rows (png_structp \fP\fIpng_ptr\fP\fB, png_bytepp \fP\fIrow\fP\fB, png_bytepp \fP\fIdisplay_row\fP\fB, png_uint_32 \fInum_rows\fP\fB);\fP
|
|---|
| 422 |
|
|---|
| 423 | \fI\fB
|
|---|
| 424 |
|
|---|
| 425 | \fBvoid png_read_update_info (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fIinfo_ptr\fP\fB);\fP
|
|---|
| 426 |
|
|---|
| 427 | \fI\fB
|
|---|
| 428 |
|
|---|
| 429 | \fB#if \fI!defined(PNG_1_0_X)
|
|---|
| 430 |
|
|---|
| 431 | \fBpng_save_int_32 (png_bytep \fP\fIbuf\fP\fB, png_int_32 \fIi\fP\fB);\fP
|
|---|
| 432 |
|
|---|
| 433 | \fI\fB
|
|---|
| 434 |
|
|---|
| 435 | \fBvoid png_save_uint_16 (png_bytep \fP\fIbuf\fP\fB, unsigned int \fIi\fP\fB);\fP
|
|---|
| 436 |
|
|---|
| 437 | \fI\fB
|
|---|
| 438 |
|
|---|
| 439 | \fBvoid png_save_uint_32 (png_bytep \fP\fIbuf\fP\fB, png_uint_32 \fIi\fP\fB);\fP
|
|---|
| 440 |
|
|---|
| 441 | \fI\fB
|
|---|
| 442 |
|
|---|
| 443 | \fBvoid png_set_add_alpha (png_structp \fP\fIpng_ptr\fP\fB, png_uint_32 \fP\fIfiller\fP\fB, int \fIflags\fP\fB);\fP
|
|---|
| 444 |
|
|---|
| 445 | \fI\fB#endif
|
|---|
| 446 |
|
|---|
| 447 | \fI\fB
|
|---|
| 448 |
|
|---|
| 449 | \fBvoid png_set_background (png_structp \fP\fIpng_ptr\fP\fB, png_color_16p \fP\fIbackground_color\fP\fB, int \fP\fIbackground_gamma_code\fP\fB, int \fP\fIneed_expand\fP\fB, double \fIbackground_gamma\fP\fB);\fP
|
|---|
| 450 |
|
|---|
| 451 | \fI\fB
|
|---|
| 452 |
|
|---|
| 453 | \fBvoid png_set_bgr (png_structp \fIpng_ptr\fP\fB);\fP
|
|---|
| 454 |
|
|---|
| 455 | \fI\fB
|
|---|
| 456 |
|
|---|
| 457 | \fBvoid png_set_bKGD (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, png_color_16p \fIbackground\fP\fB);\fP
|
|---|
| 458 |
|
|---|
| 459 | \fI\fB
|
|---|
| 460 |
|
|---|
| 461 | \fBvoid png_set_cHRM (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, double \fP\fIwhite_x\fP\fB, double \fP\fIwhite_y\fP\fB, double \fP\fIred_x\fP\fB, double \fP\fIred_y\fP\fB, double \fP\fIgreen_x\fP\fB, double \fP\fIgreen_y\fP\fB, double \fP\fIblue_x\fP\fB, double \fIblue_y\fP\fB);\fP
|
|---|
| 462 |
|
|---|
| 463 | \fI\fB
|
|---|
| 464 |
|
|---|
| 465 | \fBvoid png_set_cHRM_fixed (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, png_uint_32 \fP\fIwhite_x\fP\fB, png_uint_32 \fP\fIwhite_y\fP\fB, png_uint_32 \fP\fIred_x\fP\fB, png_uint_32 \fP\fIred_y\fP\fB, png_uint_32 \fP\fIgreen_x\fP\fB, png_uint_32 \fP\fIgreen_y\fP\fB, png_uint_32 \fP\fIblue_x\fP\fB, png_uint_32 \fIblue_y\fP\fB);\fP
|
|---|
| 466 |
|
|---|
| 467 | \fI\fB
|
|---|
| 468 |
|
|---|
| 469 | \fBvoid png_set_compression_level (png_structp \fP\fIpng_ptr\fP\fB, int \fIlevel\fP\fB);\fP
|
|---|
| 470 |
|
|---|
| 471 | \fI\fB
|
|---|
| 472 |
|
|---|
| 473 | \fBvoid png_set_compression_mem_level (png_structp \fP\fIpng_ptr\fP\fB, int \fImem_level\fP\fB);\fP
|
|---|
| 474 |
|
|---|
| 475 | \fI\fB
|
|---|
| 476 |
|
|---|
| 477 | \fBvoid png_set_compression_method (png_structp \fP\fIpng_ptr\fP\fB, int \fImethod\fP\fB);\fP
|
|---|
| 478 |
|
|---|
| 479 | \fI\fB
|
|---|
| 480 |
|
|---|
| 481 | \fBvoid png_set_compression_strategy (png_structp \fP\fIpng_ptr\fP\fB, int \fIstrategy\fP\fB);\fP
|
|---|
| 482 |
|
|---|
| 483 | \fI\fB
|
|---|
| 484 |
|
|---|
| 485 | \fBvoid png_set_compression_window_bits (png_structp \fP\fIpng_ptr\fP\fB, int \fIwindow_bits\fP\fB);\fP
|
|---|
| 486 |
|
|---|
| 487 | \fI\fB
|
|---|
| 488 |
|
|---|
| 489 | \fBvoid png_set_crc_action (png_structp \fP\fIpng_ptr\fP\fB, int \fP\fIcrit_action\fP\fB, int \fIancil_action\fP\fB);\fP
|
|---|
| 490 |
|
|---|
| 491 | \fI\fB
|
|---|
| 492 |
|
|---|
| 493 | \fBvoid png_set_dither (png_structp \fP\fIpng_ptr\fP\fB, png_colorp \fP\fIpalette\fP\fB, int \fP\fInum_palette\fP\fB, int \fP\fImaximum_colors\fP\fB, png_uint_16p \fP\fIhistogram\fP\fB, int \fIfull_dither\fP\fB);\fP
|
|---|
| 494 |
|
|---|
| 495 | \fI\fB
|
|---|
| 496 |
|
|---|
| 497 | \fBvoid png_set_error_fn (png_structp \fP\fIpng_ptr\fP\fB, png_voidp \fP\fIerror_ptr\fP\fB, png_error_ptr \fP\fIerror_fn\fP\fB, png_error_ptr \fIwarning_fn\fP\fB);\fP
|
|---|
| 498 |
|
|---|
| 499 | \fI\fB
|
|---|
| 500 |
|
|---|
| 501 | \fBvoid png_set_expand (png_structp \fIpng_ptr\fP\fB);\fP
|
|---|
| 502 |
|
|---|
| 503 | \fI\fB
|
|---|
| 504 |
|
|---|
| 505 | \fBvoid png_set_expand_gray_1_2_4_to_8(png_structp \fIpng_ptr\fP\fB);\fP
|
|---|
| 506 |
|
|---|
| 507 | \fI\fB
|
|---|
| 508 |
|
|---|
| 509 | \fBvoid png_set_filler (png_structp \fP\fIpng_ptr\fP\fB, png_uint_32 \fP\fIfiller\fP\fB, int \fIflags\fP\fB);\fP
|
|---|
| 510 |
|
|---|
| 511 | \fI\fB
|
|---|
| 512 |
|
|---|
| 513 | \fBvoid png_set_filter (png_structp \fP\fIpng_ptr\fP\fB, int \fP\fImethod\fP\fB, int \fIfilters\fP\fB);\fP
|
|---|
| 514 |
|
|---|
| 515 | \fI\fB
|
|---|
| 516 |
|
|---|
| 517 | \fBvoid png_set_filter_heuristics (png_structp \fP\fIpng_ptr\fP\fB, int \fP\fIheuristic_method\fP\fB, int \fP\fInum_weights\fP\fB, png_doublep \fP\fIfilter_weights\fP\fB, png_doublep \fIfilter_costs\fP\fB);\fP
|
|---|
| 518 |
|
|---|
| 519 | \fI\fB
|
|---|
| 520 |
|
|---|
| 521 | \fBvoid png_set_flush (png_structp \fP\fIpng_ptr\fP\fB, int \fInrows\fP\fB);\fP
|
|---|
| 522 |
|
|---|
| 523 | \fI\fB
|
|---|
| 524 |
|
|---|
| 525 | \fBvoid png_set_gamma (png_structp \fP\fIpng_ptr\fP\fB, double \fP\fIscreen_gamma\fP\fB, double \fIdefault_file_gamma\fP\fB);\fP
|
|---|
| 526 |
|
|---|
| 527 | \fI\fB
|
|---|
| 528 |
|
|---|
| 529 | \fBvoid png_set_gAMA (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, double \fIfile_gamma\fP\fB);\fP
|
|---|
| 530 |
|
|---|
| 531 | \fI\fB
|
|---|
| 532 |
|
|---|
| 533 | \fBvoid png_set_gAMA_fixed (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, png_uint_32 \fIfile_gamma\fP\fB);\fP
|
|---|
| 534 |
|
|---|
| 535 | \fI\fB
|
|---|
| 536 |
|
|---|
| 537 | \fBvoid png_set_gray_1_2_4_to_8(png_structp \fIpng_ptr\fP\fB);\fP
|
|---|
| 538 |
|
|---|
| 539 | \fI\fB
|
|---|
| 540 |
|
|---|
| 541 | \fBvoid png_set_gray_to_rgb (png_structp \fIpng_ptr\fP\fB);\fP
|
|---|
| 542 |
|
|---|
| 543 | \fI\fB
|
|---|
| 544 |
|
|---|
| 545 | \fBvoid png_set_hIST (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, png_uint_16p \fIhist\fP\fB);\fP
|
|---|
| 546 |
|
|---|
| 547 | \fI\fB
|
|---|
| 548 |
|
|---|
| 549 | \fBvoid png_set_iCCP (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, png_charp \fP\fIname\fP\fB, int \fP\fIcompression_type\fP\fB, png_charp \fP\fIprofile\fP\fB, png_uint_32 \fIproflen\fP\fB);\fP
|
|---|
| 550 |
|
|---|
| 551 | \fI\fB
|
|---|
| 552 |
|
|---|
| 553 | \fBint png_set_interlace_handling (png_structp \fIpng_ptr\fP\fB);\fP
|
|---|
| 554 |
|
|---|
| 555 | \fI\fB
|
|---|
| 556 |
|
|---|
| 557 | \fBvoid png_set_invalid (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, int \fImask\fP\fB);\fP
|
|---|
| 558 |
|
|---|
| 559 | \fI\fB
|
|---|
| 560 |
|
|---|
| 561 | \fBvoid png_set_invert_alpha (png_structp \fIpng_ptr\fP\fB);\fP
|
|---|
| 562 |
|
|---|
| 563 | \fI\fB
|
|---|
| 564 |
|
|---|
| 565 | \fBvoid png_set_invert_mono (png_structp \fIpng_ptr\fP\fB);\fP
|
|---|
| 566 |
|
|---|
| 567 | \fI\fB
|
|---|
| 568 |
|
|---|
| 569 | \fBvoid png_set_IHDR (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, png_uint_32 \fP\fIwidth\fP\fB, png_uint_32 \fP\fIheight\fP\fB, int \fP\fIbit_depth\fP\fB, int \fP\fIcolor_type\fP\fB, int \fP\fIinterlace_type\fP\fB, int \fP\fIcompression_type\fP\fB, int \fIfilter_type\fP\fB);\fP
|
|---|
| 570 |
|
|---|
| 571 | \fI\fB
|
|---|
| 572 |
|
|---|
| 573 | \fBvoid png_set_keep_unknown_chunks (png_structp \fP\fIpng_ptr\fP\fB, int \fP\fIkeep\fP\fB, png_bytep \fP\fIchunk_list\fP\fB, int \fInum_chunks\fP\fB);\fP
|
|---|
| 574 |
|
|---|
| 575 | \fI\fB
|
|---|
| 576 |
|
|---|
| 577 | \fBvoid png_set_mem_fn(png_structp \fP\fIpng_ptr\fP\fB, png_voidp \fP\fImem_ptr\fP\fB, png_malloc_ptr \fP\fImalloc_fn\fP\fB, png_free_ptr \fIfree_fn\fP\fB);\fP
|
|---|
| 578 |
|
|---|
| 579 | \fI\fB
|
|---|
| 580 |
|
|---|
| 581 | \fBvoid png_set_oFFs (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, png_uint_32 \fP\fIoffset_x\fP\fB, png_uint_32 \fP\fIoffset_y\fP\fB, int \fIunit_type\fP\fB);\fP
|
|---|
| 582 |
|
|---|
| 583 | \fI\fB
|
|---|
| 584 |
|
|---|
| 585 | \fBvoid png_set_packing (png_structp \fIpng_ptr\fP\fB);\fP
|
|---|
| 586 |
|
|---|
| 587 | \fI\fB
|
|---|
| 588 |
|
|---|
| 589 | \fBvoid png_set_packswap (png_structp \fIpng_ptr\fP\fB);\fP
|
|---|
| 590 |
|
|---|
| 591 | \fI\fB
|
|---|
| 592 |
|
|---|
| 593 | \fBvoid png_set_palette_to_rgb(png_structp \fIpng_ptr\fP\fB);\fP
|
|---|
| 594 |
|
|---|
| 595 | \fI\fB
|
|---|
| 596 |
|
|---|
| 597 | \fBvoid png_set_pCAL (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, png_charp \fP\fIpurpose\fP\fB, png_int_32 \fP\fIX0\fP\fB, png_int_32 \fP\fIX1\fP\fB, int \fP\fItype\fP\fB, int \fP\fInparams\fP\fB, png_charp \fP\fIunits\fP\fB, png_charpp \fIparams\fP\fB);\fP
|
|---|
| 598 |
|
|---|
| 599 | \fI\fB
|
|---|
| 600 |
|
|---|
| 601 | \fBvoid png_set_pHYs (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, png_uint_32 \fP\fIres_x\fP\fB, png_uint_32 \fP\fIres_y\fP\fB, int \fIunit_type\fP\fB);\fP
|
|---|
| 602 |
|
|---|
| 603 | \fI\fB
|
|---|
| 604 |
|
|---|
| 605 | \fBvoid png_set_progressive_read_fn (png_structp \fP\fIpng_ptr\fP\fB, png_voidp \fP\fIprogressive_ptr\fP\fB, png_progressive_info_ptr \fP\fIinfo_fn\fP\fB, png_progressive_row_ptr \fP\fIrow_fn\fP\fB, png_progressive_end_ptr \fIend_fn\fP\fB);\fP
|
|---|
| 606 |
|
|---|
| 607 | \fI\fB
|
|---|
| 608 |
|
|---|
| 609 | \fBvoid png_set_PLTE (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, png_colorp \fP\fIpalette\fP\fB, int \fInum_palette\fP\fB);\fP
|
|---|
| 610 |
|
|---|
| 611 | \fI\fB
|
|---|
| 612 |
|
|---|
| 613 | \fBvoid png_set_read_fn (png_structp \fP\fIpng_ptr\fP\fB, png_voidp \fP\fIio_ptr\fP\fB, png_rw_ptr \fIread_data_fn\fP\fB);\fP
|
|---|
| 614 |
|
|---|
| 615 | \fI\fB
|
|---|
| 616 |
|
|---|
| 617 | \fBvoid png_set_read_status_fn (png_structp \fP\fIpng_ptr\fP\fB, png_read_status_ptr \fIread_row_fn\fP\fB);\fP
|
|---|
| 618 |
|
|---|
| 619 | \fI\fB
|
|---|
| 620 |
|
|---|
| 621 | \fBvoid png_set_read_user_transform_fn (png_structp \fP\fIpng_ptr\fP\fB, png_user_transform_ptr \fIread_user_transform_fn\fP\fB);\fP
|
|---|
| 622 |
|
|---|
| 623 | \fI\fB
|
|---|
| 624 |
|
|---|
| 625 | \fBvoid png_set_rgb_to_gray (png_structp \fP\fIpng_ptr\fP\fB, int \fP\fIerror_action\fP\fB, double \fP\fIred\fP\fB, double \fIgreen\fP\fB);\fP
|
|---|
| 626 |
|
|---|
| 627 | \fI\fB
|
|---|
| 628 |
|
|---|
| 629 | \fBvoid png_set_rgb_to_gray_fixed (png_structp \fP\fIpng_ptr\fP\fB, int error_action png_fixed_point \fP\fIred\fP\fB, png_fixed_point \fIgreen\fP\fB);\fP
|
|---|
| 630 |
|
|---|
| 631 | \fI\fB
|
|---|
| 632 |
|
|---|
| 633 | \fBvoid png_set_rows (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, png_bytepp \fIrow_pointers\fP\fB);\fP
|
|---|
| 634 |
|
|---|
| 635 | \fI\fB
|
|---|
| 636 |
|
|---|
| 637 | \fBvoid png_set_sBIT (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, png_color_8p \fIsig_bit\fP\fB);\fP
|
|---|
| 638 |
|
|---|
| 639 | \fI\fB
|
|---|
| 640 |
|
|---|
| 641 | \fBvoid png_set_sCAL (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, png_charp \fP\fIunit\fP\fB, double \fP\fIwidth\fP\fB, double \fIheight\fP\fB);\fP
|
|---|
| 642 |
|
|---|
| 643 | \fI\fB
|
|---|
| 644 |
|
|---|
| 645 | \fBvoid png_set_shift (png_structp \fP\fIpng_ptr\fP\fB, png_color_8p \fItrue_bits\fP\fB);\fP
|
|---|
| 646 |
|
|---|
| 647 | \fI\fB
|
|---|
| 648 |
|
|---|
| 649 | \fBvoid png_set_sig_bytes (png_structp \fP\fIpng_ptr\fP\fB, int \fInum_bytes\fP\fB);\fP
|
|---|
| 650 |
|
|---|
| 651 | \fI\fB
|
|---|
| 652 |
|
|---|
| 653 | \fBvoid png_set_sPLT (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, png_spalette_p \fP\fIsplt_ptr\fP\fB, int \fInum_spalettes\fP\fB);\fP
|
|---|
| 654 |
|
|---|
| 655 | \fI\fB
|
|---|
| 656 |
|
|---|
| 657 | \fBvoid png_set_sRGB (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, int \fIintent\fP\fB);\fP
|
|---|
| 658 |
|
|---|
| 659 | \fI\fB
|
|---|
| 660 |
|
|---|
| 661 | \fBvoid png_set_sRGB_gAMA_and_cHRM (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, int \fIintent\fP\fB);\fP
|
|---|
| 662 |
|
|---|
| 663 | \fI\fB
|
|---|
| 664 |
|
|---|
| 665 | \fBvoid png_set_strip_16 (png_structp \fIpng_ptr\fP\fB);\fP
|
|---|
| 666 |
|
|---|
| 667 | \fI\fB
|
|---|
| 668 |
|
|---|
| 669 | \fBvoid png_set_strip_alpha (png_structp \fIpng_ptr\fP\fB);\fP
|
|---|
| 670 |
|
|---|
| 671 | \fI\fB
|
|---|
| 672 |
|
|---|
| 673 | \fBvoid png_set_swap (png_structp \fIpng_ptr\fP\fB);\fP
|
|---|
| 674 |
|
|---|
| 675 | \fI\fB
|
|---|
| 676 |
|
|---|
| 677 | \fBvoid png_set_swap_alpha (png_structp \fIpng_ptr\fP\fB);\fP
|
|---|
| 678 |
|
|---|
| 679 | \fI\fB
|
|---|
| 680 |
|
|---|
| 681 | \fBvoid png_set_text (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, png_textp \fP\fItext_ptr\fP\fB, int \fInum_text\fP\fB);\fP
|
|---|
| 682 |
|
|---|
| 683 | \fI\fB
|
|---|
| 684 |
|
|---|
| 685 | \fBvoid png_set_tIME (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, png_timep \fImod_time\fP\fB);\fP
|
|---|
| 686 |
|
|---|
| 687 | \fI\fB
|
|---|
| 688 |
|
|---|
| 689 | \fBvoid png_set_tRNS (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, png_bytep \fP\fItrans\fP\fB, int \fP\fInum_trans\fP\fB, png_color_16p \fItrans_values\fP\fB);\fP
|
|---|
| 690 |
|
|---|
| 691 | \fI\fB
|
|---|
| 692 |
|
|---|
| 693 | \fBvoid png_set_tRNS_to_alpha(png_structp \fIpng_ptr\fP\fB);\fP
|
|---|
| 694 |
|
|---|
| 695 | \fI\fB
|
|---|
| 696 |
|
|---|
| 697 | \fBpng_uint_32 png_set_unknown_chunks (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, png_unknown_chunkp \fP\fIunknowns\fP\fB, int \fP\fInum\fP\fB, int \fIlocation\fP\fB);\fP
|
|---|
| 698 |
|
|---|
| 699 | \fI\fB
|
|---|
| 700 |
|
|---|
| 701 | \fBvoid png_set_unknown_chunk_location(png_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, int \fP\fIchunk\fP\fB, int \fIlocation\fP\fB);\fP
|
|---|
| 702 |
|
|---|
| 703 | \fI\fB
|
|---|
| 704 |
|
|---|
| 705 | \fBvoid png_set_read_user_chunk_fn (png_structp \fP\fIpng_ptr\fP\fB, png_voidp \fP\fIuser_chunk_ptr\fP\fB, png_user_chunk_ptr \fIread_user_chunk_fn\fP\fB);\fP
|
|---|
| 706 |
|
|---|
| 707 | \fI\fB
|
|---|
| 708 |
|
|---|
| 709 | \fBvoid png_set_user_limits (png_structp \fP\fIpng_ptr\fP\fB, png_uint_32 \fP\fIuser_width_max\fP\fB, png_uint_32 \fIuser_height_max\fP\fB);\fP
|
|---|
| 710 |
|
|---|
| 711 | \fI\fB
|
|---|
| 712 |
|
|---|
| 713 | \fBvoid png_set_user_transform_info (png_structp \fP\fIpng_ptr\fP\fB, png_voidp \fP\fIuser_transform_ptr\fP\fB, int \fP\fIuser_transform_depth\fP\fB, int \fIuser_transform_channels\fP\fB);\fP
|
|---|
| 714 |
|
|---|
| 715 | \fI\fB
|
|---|
| 716 |
|
|---|
| 717 | \fBvoid png_set_write_fn (png_structp \fP\fIpng_ptr\fP\fB, png_voidp \fP\fIio_ptr\fP\fB, png_rw_ptr \fP\fIwrite_data_fn\fP\fB, png_flush_ptr \fIoutput_flush_fn\fP\fB);\fP
|
|---|
| 718 |
|
|---|
| 719 | \fI\fB
|
|---|
| 720 |
|
|---|
| 721 | \fBvoid png_set_write_status_fn (png_structp \fP\fIpng_ptr\fP\fB, png_write_status_ptr \fIwrite_row_fn\fP\fB);\fP
|
|---|
| 722 |
|
|---|
| 723 | \fI\fB
|
|---|
| 724 |
|
|---|
| 725 | \fBvoid png_set_write_user_transform_fn (png_structp \fP\fIpng_ptr\fP\fB, png_user_transform_ptr \fIwrite_user_transform_fn\fP\fB);\fP
|
|---|
| 726 |
|
|---|
| 727 | \fI\fB
|
|---|
| 728 |
|
|---|
| 729 | \fBvoid png_set_compression_buffer_size(png_structp \fP\fIpng_ptr\fP\fB, png_uint_32 \fIsize\fP\fB);\fP
|
|---|
| 730 |
|
|---|
| 731 | \fI\fB
|
|---|
| 732 |
|
|---|
| 733 | \fBint png_sig_cmp (png_bytep \fP\fIsig\fP\fB, png_size_t \fP\fIstart\fP\fB, png_size_t \fInum_to_check\fP\fB);\fP
|
|---|
| 734 |
|
|---|
| 735 | \fI\fB
|
|---|
| 736 |
|
|---|
| 737 | \fBvoid png_start_read_image (png_structp \fIpng_ptr\fP\fB);\fP
|
|---|
| 738 |
|
|---|
| 739 | \fI\fB
|
|---|
| 740 |
|
|---|
| 741 | \fBvoid png_warning (png_structp \fP\fIpng_ptr\fP\fB, png_const_charp \fImessage\fP\fB);\fP
|
|---|
| 742 |
|
|---|
| 743 | \fI\fB
|
|---|
| 744 |
|
|---|
| 745 | \fBvoid png_write_chunk (png_structp \fP\fIpng_ptr\fP\fB, png_bytep \fP\fIchunk_name\fP\fB, png_bytep \fP\fIdata\fP\fB, png_size_t \fIlength\fP\fB);\fP
|
|---|
| 746 |
|
|---|
| 747 | \fI\fB
|
|---|
| 748 |
|
|---|
| 749 | \fBvoid png_write_chunk_data (png_structp \fP\fIpng_ptr\fP\fB, png_bytep \fP\fIdata\fP\fB, png_size_t \fIlength\fP\fB);\fP
|
|---|
| 750 |
|
|---|
| 751 | \fI\fB
|
|---|
| 752 |
|
|---|
| 753 | \fBvoid png_write_chunk_end (png_structp \fIpng_ptr\fP\fB);\fP
|
|---|
| 754 |
|
|---|
| 755 | \fI\fB
|
|---|
| 756 |
|
|---|
| 757 | \fBvoid png_write_chunk_start (png_structp \fP\fIpng_ptr\fP\fB, png_bytep \fP\fIchunk_name\fP\fB, png_uint_32 \fIlength\fP\fB);\fP
|
|---|
| 758 |
|
|---|
| 759 | \fI\fB
|
|---|
| 760 |
|
|---|
| 761 | \fBvoid png_write_destroy (png_structp \fIpng_ptr\fP\fB);\fP
|
|---|
| 762 |
|
|---|
| 763 | \fI\fB
|
|---|
| 764 |
|
|---|
| 765 | \fBvoid png_write_end (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fIinfo_ptr\fP\fB);\fP
|
|---|
| 766 |
|
|---|
| 767 | \fI\fB
|
|---|
| 768 |
|
|---|
| 769 | \fBvoid png_write_flush (png_structp \fIpng_ptr\fP\fB);\fP
|
|---|
| 770 |
|
|---|
| 771 | \fI\fB
|
|---|
| 772 |
|
|---|
| 773 | \fBvoid png_write_image (png_structp \fP\fIpng_ptr\fP\fB, png_bytepp \fIimage\fP\fB);\fP
|
|---|
| 774 |
|
|---|
| 775 | \fI\fB
|
|---|
| 776 |
|
|---|
| 777 | \fBDEPRECATED: void png_write_init (png_structp \fIpng_ptr\fP\fB);\fP
|
|---|
| 778 |
|
|---|
| 779 | \fI\fB
|
|---|
| 780 |
|
|---|
| 781 | \fBDEPRECATED: void png_write_init_2 (png_structpp \fP\fIptr_ptr\fP\fB, png_const_charp \fP\fIuser_png_ver\fP\fB, png_size_t \fP\fIpng_struct_size\fP\fB, png_size_t \fIpng_info_size\fP\fB);\fP
|
|---|
| 782 |
|
|---|
| 783 | \fI\fB
|
|---|
| 784 |
|
|---|
| 785 | \fBvoid png_write_info (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fIinfo_ptr\fP\fB);\fP
|
|---|
| 786 |
|
|---|
| 787 | \fI\fB
|
|---|
| 788 |
|
|---|
| 789 | \fBvoid png_write_info_before_PLTE (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fIinfo_ptr\fP\fB);\fP
|
|---|
| 790 |
|
|---|
| 791 | \fI\fB
|
|---|
| 792 |
|
|---|
| 793 | \fBvoid png_write_png (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, int \fP\fItransforms\fP\fB, png_voidp \fIparams\fP\fB);\fP
|
|---|
| 794 |
|
|---|
| 795 | \fI\fB
|
|---|
| 796 |
|
|---|
| 797 | \fBvoid png_write_row (png_structp \fP\fIpng_ptr\fP\fB, png_bytep \fIrow\fP\fB);\fP
|
|---|
| 798 |
|
|---|
| 799 | \fI\fB
|
|---|
| 800 |
|
|---|
| 801 | \fBvoid png_write_rows (png_structp \fP\fIpng_ptr\fP\fB, png_bytepp \fP\fIrow\fP\fB, png_uint_32 \fInum_rows\fP\fB);\fP
|
|---|
| 802 |
|
|---|
| 803 | \fI\fB
|
|---|
| 804 |
|
|---|
| 805 | \fBvoidpf png_zalloc (voidpf \fP\fIpng_ptr\fP\fB, uInt \fP\fIitems\fP\fB, uInt \fIsize\fP\fB);\fP
|
|---|
| 806 |
|
|---|
| 807 | \fI\fB
|
|---|
| 808 |
|
|---|
| 809 | \fBvoid png_zfree (voidpf \fP\fIpng_ptr\fP\fB, voidpf \fIptr\fP\fB);\fP
|
|---|
| 810 |
|
|---|
| 811 | \fI\fB
|
|---|
| 812 |
|
|---|
| 813 | .SH DESCRIPTION
|
|---|
| 814 | The
|
|---|
| 815 | .I libpng
|
|---|
| 816 | library supports encoding, decoding, and various manipulations of
|
|---|
| 817 | the Portable Network Graphics (PNG) format image files. It uses the
|
|---|
| 818 | .IR zlib(3)
|
|---|
| 819 | compression library.
|
|---|
| 820 | Following is a copy of the libpng.txt file that accompanies libpng.
|
|---|
| 821 | .SH LIBPNG.TXT
|
|---|
| 822 | libpng.txt - A description on how to use and modify libpng
|
|---|
| 823 |
|
|---|
| 824 | libpng version 1.2.40 - September 10, 2009
|
|---|
| 825 | Updated and distributed by Glenn Randers-Pehrson
|
|---|
| 826 | <glennrp at users.sourceforge.net>
|
|---|
| 827 | Copyright (c) 1998-2009 Glenn Randers-Pehrson
|
|---|
| 828 |
|
|---|
| 829 | This document is released under the libpng license.
|
|---|
| 830 | For conditions of distribution and use, see the disclaimer
|
|---|
| 831 | and license in png.h
|
|---|
| 832 |
|
|---|
| 833 | Based on:
|
|---|
| 834 |
|
|---|
| 835 | libpng versions 0.97, January 1998, through 1.2.40 - September 10, 2009
|
|---|
| 836 | Updated and distributed by Glenn Randers-Pehrson
|
|---|
| 837 | Copyright (c) 1998-2009 Glenn Randers-Pehrson
|
|---|
| 838 |
|
|---|
| 839 | libpng 1.0 beta 6 version 0.96 May 28, 1997
|
|---|
| 840 | Updated and distributed by Andreas Dilger
|
|---|
| 841 | Copyright (c) 1996, 1997 Andreas Dilger
|
|---|
| 842 |
|
|---|
| 843 | libpng 1.0 beta 2 - version 0.88 January 26, 1996
|
|---|
| 844 | For conditions of distribution and use, see copyright
|
|---|
| 845 | notice in png.h. Copyright (c) 1995, 1996 Guy Eric
|
|---|
| 846 | Schalnat, Group 42, Inc.
|
|---|
| 847 |
|
|---|
| 848 | Updated/rewritten per request in the libpng FAQ
|
|---|
| 849 | Copyright (c) 1995, 1996 Frank J. T. Wojcik
|
|---|
| 850 | December 18, 1995 & January 20, 1996
|
|---|
| 851 |
|
|---|
| 852 | .SH I. Introduction
|
|---|
| 853 |
|
|---|
| 854 | This file describes how to use and modify the PNG reference library
|
|---|
| 855 | (known as libpng) for your own use. There are five sections to this
|
|---|
| 856 | file: introduction, structures, reading, writing, and modification and
|
|---|
| 857 | configuration notes for various special platforms. In addition to this
|
|---|
| 858 | file, example.c is a good starting point for using the library, as
|
|---|
| 859 | it is heavily commented and should include everything most people
|
|---|
| 860 | will need. We assume that libpng is already installed; see the
|
|---|
| 861 | INSTALL file for instructions on how to install libpng.
|
|---|
| 862 |
|
|---|
| 863 | For examples of libpng usage, see the files "example.c", "pngtest.c",
|
|---|
| 864 | and the files in the "contrib" directory, all of which are included in the
|
|---|
| 865 | libpng distribution.
|
|---|
| 866 |
|
|---|
| 867 | Libpng was written as a companion to the PNG specification, as a way
|
|---|
| 868 | of reducing the amount of time and effort it takes to support the PNG
|
|---|
| 869 | file format in application programs.
|
|---|
| 870 |
|
|---|
| 871 | The PNG specification (second edition), November 2003, is available as
|
|---|
| 872 | a W3C Recommendation and as an ISO Standard (ISO/IEC 15948:2003 (E)) at
|
|---|
| 873 | <http://www.w3.org/TR/2003/REC-PNG-20031110/
|
|---|
| 874 | The W3C and ISO documents have identical technical content.
|
|---|
| 875 |
|
|---|
| 876 | The PNG-1.2 specification is available at
|
|---|
| 877 | <http://www.libpng.org/pub/png/documents/>. It is technically equivalent
|
|---|
| 878 | to the PNG specification (second edition) but has some additional material.
|
|---|
| 879 |
|
|---|
| 880 | The PNG-1.0 specification is available
|
|---|
| 881 | as RFC 2083 <http://www.libpng.org/pub/png/documents/> and as a
|
|---|
| 882 | W3C Recommendation <http://www.w3.org/TR/REC.png.html>.
|
|---|
| 883 |
|
|---|
| 884 | Some additional chunks are described in the special-purpose public chunks
|
|---|
| 885 | documents at <http://www.libpng.org/pub/png/documents/>.
|
|---|
| 886 |
|
|---|
| 887 | Other information
|
|---|
| 888 | about PNG, and the latest version of libpng, can be found at the PNG home
|
|---|
| 889 | page, <http://www.libpng.org/pub/png/>.
|
|---|
| 890 |
|
|---|
| 891 | Most users will not have to modify the library significantly; advanced
|
|---|
| 892 | users may want to modify it more. All attempts were made to make it as
|
|---|
| 893 | complete as possible, while keeping the code easy to understand.
|
|---|
| 894 | Currently, this library only supports C. Support for other languages
|
|---|
| 895 | is being considered.
|
|---|
| 896 |
|
|---|
| 897 | Libpng has been designed to handle multiple sessions at one time,
|
|---|
| 898 | to be easily modifiable, to be portable to the vast majority of
|
|---|
| 899 | machines (ANSI, K&R, 16-, 32-, and 64-bit) available, and to be easy
|
|---|
| 900 | to use. The ultimate goal of libpng is to promote the acceptance of
|
|---|
| 901 | the PNG file format in whatever way possible. While there is still
|
|---|
| 902 | work to be done (see the TODO file), libpng should cover the
|
|---|
| 903 | majority of the needs of its users.
|
|---|
| 904 |
|
|---|
| 905 | Libpng uses zlib for its compression and decompression of PNG files.
|
|---|
| 906 | Further information about zlib, and the latest version of zlib, can
|
|---|
| 907 | be found at the zlib home page, <http://www.info-zip.org/pub/infozip/zlib/>.
|
|---|
| 908 | The zlib compression utility is a general purpose utility that is
|
|---|
| 909 | useful for more than PNG files, and can be used without libpng.
|
|---|
| 910 | See the documentation delivered with zlib for more details.
|
|---|
| 911 | You can usually find the source files for the zlib utility wherever you
|
|---|
| 912 | find the libpng source files.
|
|---|
| 913 |
|
|---|
| 914 | Libpng is thread safe, provided the threads are using different
|
|---|
| 915 | instances of the structures. Each thread should have its own
|
|---|
| 916 | png_struct and png_info instances, and thus its own image.
|
|---|
| 917 | Libpng does not protect itself against two threads using the
|
|---|
| 918 | same instance of a structure.
|
|---|
| 919 |
|
|---|
| 920 | .SH II. Structures
|
|---|
| 921 |
|
|---|
| 922 | There are two main structures that are important to libpng, png_struct
|
|---|
| 923 | and png_info. The first, png_struct, is an internal structure that
|
|---|
| 924 | will not, for the most part, be used by a user except as the first
|
|---|
| 925 | variable passed to every libpng function call.
|
|---|
| 926 |
|
|---|
| 927 | The png_info structure is designed to provide information about the
|
|---|
| 928 | PNG file. At one time, the fields of png_info were intended to be
|
|---|
| 929 | directly accessible to the user. However, this tended to cause problems
|
|---|
| 930 | with applications using dynamically loaded libraries, and as a result
|
|---|
| 931 | a set of interface functions for png_info (the png_get_*() and png_set_*()
|
|---|
| 932 | functions) was developed. The fields of png_info are still available for
|
|---|
| 933 | older applications, but it is suggested that applications use the new
|
|---|
| 934 | interfaces if at all possible.
|
|---|
| 935 |
|
|---|
| 936 | Applications that do make direct access to the members of png_struct (except
|
|---|
| 937 | for png_ptr->jmpbuf) must be recompiled whenever the library is updated,
|
|---|
| 938 | and applications that make direct access to the members of png_info must
|
|---|
| 939 | be recompiled if they were compiled or loaded with libpng version 1.0.6,
|
|---|
| 940 | in which the members were in a different order. In version 1.0.7, the
|
|---|
| 941 | members of the png_info structure reverted to the old order, as they were
|
|---|
| 942 | in versions 0.97c through 1.0.5. Starting with version 2.0.0, both
|
|---|
| 943 | structures are going to be hidden, and the contents of the structures will
|
|---|
| 944 | only be accessible through the png_get/png_set functions.
|
|---|
| 945 |
|
|---|
| 946 | The png.h header file is an invaluable reference for programming with libpng.
|
|---|
| 947 | And while I'm on the topic, make sure you include the libpng header file:
|
|---|
| 948 |
|
|---|
| 949 | #include <png.h>
|
|---|
| 950 |
|
|---|
| 951 | .SH III. Reading
|
|---|
| 952 |
|
|---|
| 953 | We'll now walk you through the possible functions to call when reading
|
|---|
| 954 | in a PNG file sequentially, briefly explaining the syntax and purpose
|
|---|
| 955 | of each one. See example.c and png.h for more detail. While
|
|---|
| 956 | progressive reading is covered in the next section, you will still
|
|---|
| 957 | need some of the functions discussed in this section to read a PNG
|
|---|
| 958 | file.
|
|---|
| 959 |
|
|---|
| 960 | .SS Setup
|
|---|
| 961 |
|
|---|
| 962 | You will want to do the I/O initialization(*) before you get into libpng,
|
|---|
| 963 | so if it doesn't work, you don't have much to undo. Of course, you
|
|---|
| 964 | will also want to insure that you are, in fact, dealing with a PNG
|
|---|
| 965 | file. Libpng provides a simple check to see if a file is a PNG file.
|
|---|
| 966 | To use it, pass in the first 1 to 8 bytes of the file to the function
|
|---|
| 967 | png_sig_cmp(), and it will return 0 (false) if the bytes match the
|
|---|
| 968 | corresponding bytes of the PNG signature, or nonzero (true) otherwise.
|
|---|
| 969 | Of course, the more bytes you pass in, the greater the accuracy of the
|
|---|
| 970 | prediction.
|
|---|
| 971 |
|
|---|
| 972 | If you are intending to keep the file pointer open for use in libpng,
|
|---|
| 973 | you must ensure you don't read more than 8 bytes from the beginning
|
|---|
| 974 | of the file, and you also have to make a call to png_set_sig_bytes_read()
|
|---|
| 975 | with the number of bytes you read from the beginning. Libpng will
|
|---|
| 976 | then only check the bytes (if any) that your program didn't read.
|
|---|
| 977 |
|
|---|
| 978 | (*): If you are not using the standard I/O functions, you will need
|
|---|
| 979 | to replace them with custom functions. See the discussion under
|
|---|
| 980 | Customizing libpng.
|
|---|
| 981 |
|
|---|
| 982 |
|
|---|
| 983 | FILE *fp = fopen(file_name, "rb");
|
|---|
| 984 | if (!fp)
|
|---|
| 985 | {
|
|---|
| 986 | return (ERROR);
|
|---|
| 987 | }
|
|---|
| 988 | fread(header, 1, number, fp);
|
|---|
| 989 | is_png = !png_sig_cmp(header, 0, number);
|
|---|
| 990 | if (!is_png)
|
|---|
| 991 | {
|
|---|
| 992 | return (NOT_PNG);
|
|---|
| 993 | }
|
|---|
| 994 |
|
|---|
| 995 |
|
|---|
| 996 | Next, png_struct and png_info need to be allocated and initialized. In
|
|---|
| 997 | order to ensure that the size of these structures is correct even with a
|
|---|
| 998 | dynamically linked libpng, there are functions to initialize and
|
|---|
| 999 | allocate the structures. We also pass the library version, optional
|
|---|
| 1000 | pointers to error handling functions, and a pointer to a data struct for
|
|---|
| 1001 | use by the error functions, if necessary (the pointer and functions can
|
|---|
| 1002 | be NULL if the default error handlers are to be used). See the section
|
|---|
| 1003 | on Changes to Libpng below regarding the old initialization functions.
|
|---|
| 1004 | The structure allocation functions quietly return NULL if they fail to
|
|---|
| 1005 | create the structure, so your application should check for that.
|
|---|
| 1006 |
|
|---|
| 1007 | png_structp png_ptr = png_create_read_struct
|
|---|
| 1008 | (PNG_LIBPNG_VER_STRING, (png_voidp)user_error_ptr,
|
|---|
| 1009 | user_error_fn, user_warning_fn);
|
|---|
| 1010 | if (!png_ptr)
|
|---|
| 1011 | return (ERROR);
|
|---|
| 1012 |
|
|---|
| 1013 | png_infop info_ptr = png_create_info_struct(png_ptr);
|
|---|
| 1014 | if (!info_ptr)
|
|---|
| 1015 | {
|
|---|
| 1016 | png_destroy_read_struct(&png_ptr,
|
|---|
| 1017 | (png_infopp)NULL, (png_infopp)NULL);
|
|---|
| 1018 | return (ERROR);
|
|---|
| 1019 | }
|
|---|
| 1020 |
|
|---|
| 1021 | png_infop end_info = png_create_info_struct(png_ptr);
|
|---|
| 1022 | if (!end_info)
|
|---|
| 1023 | {
|
|---|
| 1024 | png_destroy_read_struct(&png_ptr, &info_ptr,
|
|---|
| 1025 | (png_infopp)NULL);
|
|---|
| 1026 | return (ERROR);
|
|---|
| 1027 | }
|
|---|
| 1028 |
|
|---|
| 1029 | If you want to use your own memory allocation routines,
|
|---|
| 1030 | define PNG_USER_MEM_SUPPORTED and use
|
|---|
| 1031 | png_create_read_struct_2() instead of png_create_read_struct():
|
|---|
| 1032 |
|
|---|
| 1033 | png_structp png_ptr = png_create_read_struct_2
|
|---|
| 1034 | (PNG_LIBPNG_VER_STRING, (png_voidp)user_error_ptr,
|
|---|
| 1035 | user_error_fn, user_warning_fn, (png_voidp)
|
|---|
| 1036 | user_mem_ptr, user_malloc_fn, user_free_fn);
|
|---|
| 1037 |
|
|---|
| 1038 | The error handling routines passed to png_create_read_struct()
|
|---|
| 1039 | and the memory alloc/free routines passed to png_create_struct_2()
|
|---|
| 1040 | are only necessary if you are not using the libpng supplied error
|
|---|
| 1041 | handling and memory alloc/free functions.
|
|---|
| 1042 |
|
|---|
| 1043 | When libpng encounters an error, it expects to longjmp back
|
|---|
| 1044 | to your routine. Therefore, you will need to call setjmp and pass
|
|---|
| 1045 | your png_jmpbuf(png_ptr). If you read the file from different
|
|---|
| 1046 | routines, you will need to update the jmpbuf field every time you enter
|
|---|
| 1047 | a new routine that will call a png_*() function.
|
|---|
| 1048 |
|
|---|
| 1049 | See your documentation of setjmp/longjmp for your compiler for more
|
|---|
| 1050 | information on setjmp/longjmp. See the discussion on libpng error
|
|---|
| 1051 | handling in the Customizing Libpng section below for more information
|
|---|
| 1052 | on the libpng error handling. If an error occurs, and libpng longjmp's
|
|---|
| 1053 | back to your setjmp, you will want to call png_destroy_read_struct() to
|
|---|
| 1054 | free any memory.
|
|---|
| 1055 |
|
|---|
| 1056 | if (setjmp(png_jmpbuf(png_ptr)))
|
|---|
| 1057 | {
|
|---|
| 1058 | png_destroy_read_struct(&png_ptr, &info_ptr,
|
|---|
| 1059 | &end_info);
|
|---|
| 1060 | fclose(fp);
|
|---|
| 1061 | return (ERROR);
|
|---|
| 1062 | }
|
|---|
| 1063 |
|
|---|
| 1064 | If you would rather avoid the complexity of setjmp/longjmp issues,
|
|---|
| 1065 | you can compile libpng with PNG_SETJMP_NOT_SUPPORTED, in which case
|
|---|
| 1066 | errors will result in a call to PNG_ABORT() which defaults to abort().
|
|---|
| 1067 |
|
|---|
| 1068 | Now you need to set up the input code. The default for libpng is to
|
|---|
| 1069 | use the C function fread(). If you use this, you will need to pass a
|
|---|
| 1070 | valid FILE * in the function png_init_io(). Be sure that the file is
|
|---|
| 1071 | opened in binary mode. If you wish to handle reading data in another
|
|---|
| 1072 | way, you need not call the png_init_io() function, but you must then
|
|---|
| 1073 | implement the libpng I/O methods discussed in the Customizing Libpng
|
|---|
| 1074 | section below.
|
|---|
| 1075 |
|
|---|
| 1076 | png_init_io(png_ptr, fp);
|
|---|
| 1077 |
|
|---|
| 1078 | If you had previously opened the file and read any of the signature from
|
|---|
| 1079 | the beginning in order to see if this was a PNG file, you need to let
|
|---|
| 1080 | libpng know that there are some bytes missing from the start of the file.
|
|---|
| 1081 |
|
|---|
| 1082 | png_set_sig_bytes(png_ptr, number);
|
|---|
| 1083 |
|
|---|
| 1084 | .SS Setting up callback code
|
|---|
| 1085 |
|
|---|
| 1086 | You can set up a callback function to handle any unknown chunks in the
|
|---|
| 1087 | input stream. You must supply the function
|
|---|
| 1088 |
|
|---|
| 1089 | read_chunk_callback(png_ptr ptr,
|
|---|
| 1090 | png_unknown_chunkp chunk);
|
|---|
| 1091 | {
|
|---|
| 1092 | /* The unknown chunk structure contains your
|
|---|
| 1093 | chunk data, along with similar data for any other
|
|---|
| 1094 | unknown chunks: */
|
|---|
| 1095 |
|
|---|
| 1096 | png_byte name[5];
|
|---|
| 1097 | png_byte *data;
|
|---|
| 1098 | png_size_t size;
|
|---|
| 1099 |
|
|---|
| 1100 | /* Note that libpng has already taken care of
|
|---|
| 1101 | the CRC handling */
|
|---|
| 1102 |
|
|---|
| 1103 | /* put your code here. Search for your chunk in the
|
|---|
| 1104 | unknown chunk structure, process it, and return one
|
|---|
| 1105 | of the following: */
|
|---|
| 1106 |
|
|---|
| 1107 | return (-n); /* chunk had an error */
|
|---|
| 1108 | return (0); /* did not recognize */
|
|---|
| 1109 | return (n); /* success */
|
|---|
| 1110 | }
|
|---|
| 1111 |
|
|---|
| 1112 | (You can give your function another name that you like instead of
|
|---|
| 1113 | "read_chunk_callback")
|
|---|
| 1114 |
|
|---|
| 1115 | To inform libpng about your function, use
|
|---|
| 1116 |
|
|---|
| 1117 | png_set_read_user_chunk_fn(png_ptr, user_chunk_ptr,
|
|---|
| 1118 | read_chunk_callback);
|
|---|
| 1119 |
|
|---|
| 1120 | This names not only the callback function, but also a user pointer that
|
|---|
| 1121 | you can retrieve with
|
|---|
| 1122 |
|
|---|
| 1123 | png_get_user_chunk_ptr(png_ptr);
|
|---|
| 1124 |
|
|---|
| 1125 | If you call the png_set_read_user_chunk_fn() function, then all unknown
|
|---|
| 1126 | chunks will be saved when read, in case your callback function will need
|
|---|
| 1127 | one or more of them. This behavior can be changed with the
|
|---|
| 1128 | png_set_keep_unknown_chunks() function, described below.
|
|---|
| 1129 |
|
|---|
| 1130 | At this point, you can set up a callback function that will be
|
|---|
| 1131 | called after each row has been read, which you can use to control
|
|---|
| 1132 | a progress meter or the like. It's demonstrated in pngtest.c.
|
|---|
| 1133 | You must supply a function
|
|---|
| 1134 |
|
|---|
| 1135 | void read_row_callback(png_ptr ptr, png_uint_32 row,
|
|---|
| 1136 | int pass);
|
|---|
| 1137 | {
|
|---|
| 1138 | /* put your code here */
|
|---|
| 1139 | }
|
|---|
| 1140 |
|
|---|
| 1141 | (You can give it another name that you like instead of "read_row_callback")
|
|---|
| 1142 |
|
|---|
| 1143 | To inform libpng about your function, use
|
|---|
| 1144 |
|
|---|
| 1145 | png_set_read_status_fn(png_ptr, read_row_callback);
|
|---|
| 1146 |
|
|---|
| 1147 | .SS Unknown-chunk handling
|
|---|
| 1148 |
|
|---|
| 1149 | Now you get to set the way the library processes unknown chunks in the
|
|---|
| 1150 | input PNG stream. Both known and unknown chunks will be read. Normal
|
|---|
| 1151 | behavior is that known chunks will be parsed into information in
|
|---|
| 1152 | various info_ptr members while unknown chunks will be discarded. This
|
|---|
| 1153 | behavior can be wasteful if your application will never use some known
|
|---|
| 1154 | chunk types. To change this, you can call:
|
|---|
| 1155 |
|
|---|
| 1156 | png_set_keep_unknown_chunks(png_ptr, keep,
|
|---|
| 1157 | chunk_list, num_chunks);
|
|---|
| 1158 | keep - 0: default unknown chunk handling
|
|---|
| 1159 | 1: ignore; do not keep
|
|---|
| 1160 | 2: keep only if safe-to-copy
|
|---|
| 1161 | 3: keep even if unsafe-to-copy
|
|---|
| 1162 | You can use these definitions:
|
|---|
| 1163 | PNG_HANDLE_CHUNK_AS_DEFAULT 0
|
|---|
| 1164 | PNG_HANDLE_CHUNK_NEVER 1
|
|---|
| 1165 | PNG_HANDLE_CHUNK_IF_SAFE 2
|
|---|
| 1166 | PNG_HANDLE_CHUNK_ALWAYS 3
|
|---|
| 1167 | chunk_list - list of chunks affected (a byte string,
|
|---|
| 1168 | five bytes per chunk, NULL or '\0' if
|
|---|
| 1169 | num_chunks is 0)
|
|---|
| 1170 | num_chunks - number of chunks affected; if 0, all
|
|---|
| 1171 | unknown chunks are affected. If nonzero,
|
|---|
| 1172 | only the chunks in the list are affected
|
|---|
| 1173 |
|
|---|
| 1174 | Unknown chunks declared in this way will be saved as raw data onto a
|
|---|
| 1175 | list of png_unknown_chunk structures. If a chunk that is normally
|
|---|
| 1176 | known to libpng is named in the list, it will be handled as unknown,
|
|---|
| 1177 | according to the "keep" directive. If a chunk is named in successive
|
|---|
| 1178 | instances of png_set_keep_unknown_chunks(), the final instance will
|
|---|
| 1179 | take precedence. The IHDR and IEND chunks should not be named in
|
|---|
| 1180 | chunk_list; if they are, libpng will process them normally anyway.
|
|---|
| 1181 |
|
|---|
| 1182 | Here is an example of the usage of png_set_keep_unknown_chunks(),
|
|---|
| 1183 | where the private "vpAg" chunk will later be processed by a user chunk
|
|---|
| 1184 | callback function:
|
|---|
| 1185 |
|
|---|
| 1186 | png_byte vpAg[5]={118, 112, 65, 103, (png_byte) '\0'};
|
|---|
| 1187 |
|
|---|
| 1188 | #if defined(PNG_UNKNOWN_CHUNKS_SUPPORTED)
|
|---|
| 1189 | png_byte unused_chunks[]=
|
|---|
| 1190 | {
|
|---|
| 1191 | 104, 73, 83, 84, (png_byte) '\0', /* hIST */
|
|---|
| 1192 | 105, 84, 88, 116, (png_byte) '\0', /* iTXt */
|
|---|
| 1193 | 112, 67, 65, 76, (png_byte) '\0', /* pCAL */
|
|---|
| 1194 | 115, 67, 65, 76, (png_byte) '\0', /* sCAL */
|
|---|
| 1195 | 115, 80, 76, 84, (png_byte) '\0', /* sPLT */
|
|---|
| 1196 | 116, 73, 77, 69, (png_byte) '\0', /* tIME */
|
|---|
| 1197 | };
|
|---|
| 1198 | #endif
|
|---|
| 1199 |
|
|---|
| 1200 | ...
|
|---|
| 1201 |
|
|---|
| 1202 | #if defined(PNG_UNKNOWN_CHUNKS_SUPPORTED)
|
|---|
| 1203 | /* ignore all unknown chunks: */
|
|---|
| 1204 | png_set_keep_unknown_chunks(read_ptr, 1, NULL, 0);
|
|---|
| 1205 | /* except for vpAg: */
|
|---|
| 1206 | png_set_keep_unknown_chunks(read_ptr, 2, vpAg, 1);
|
|---|
| 1207 | /* also ignore unused known chunks: */
|
|---|
| 1208 | png_set_keep_unknown_chunks(read_ptr, 1, unused_chunks,
|
|---|
| 1209 | (int)sizeof(unused_chunks)/5);
|
|---|
| 1210 | #endif
|
|---|
| 1211 |
|
|---|
| 1212 | .SS User limits
|
|---|
| 1213 |
|
|---|
| 1214 | The PNG specification allows the width and height of an image to be as
|
|---|
| 1215 | large as 2^31-1 (0x7fffffff), or about 2.147 billion rows and columns.
|
|---|
| 1216 | Since very few applications really need to process such large images,
|
|---|
| 1217 | we have imposed an arbitrary 1-million limit on rows and columns.
|
|---|
| 1218 | Larger images will be rejected immediately with a png_error() call. If
|
|---|
| 1219 | you wish to override this limit, you can use
|
|---|
| 1220 |
|
|---|
| 1221 | png_set_user_limits(png_ptr, width_max, height_max);
|
|---|
| 1222 |
|
|---|
| 1223 | to set your own limits, or use width_max = height_max = 0x7fffffffL
|
|---|
| 1224 | to allow all valid dimensions (libpng may reject some very large images
|
|---|
| 1225 | anyway because of potential buffer overflow conditions).
|
|---|
| 1226 |
|
|---|
| 1227 | You should put this statement after you create the PNG structure and
|
|---|
| 1228 | before calling png_read_info(), png_read_png(), or png_process_data().
|
|---|
| 1229 | If you need to retrieve the limits that are being applied, use
|
|---|
| 1230 |
|
|---|
| 1231 | width_max = png_get_user_width_max(png_ptr);
|
|---|
| 1232 | height_max = png_get_user_height_max(png_ptr);
|
|---|
| 1233 |
|
|---|
| 1234 | .SS The high-level read interface
|
|---|
| 1235 |
|
|---|
| 1236 | At this point there are two ways to proceed; through the high-level
|
|---|
| 1237 | read interface, or through a sequence of low-level read operations.
|
|---|
| 1238 | You can use the high-level interface if (a) you are willing to read
|
|---|
| 1239 | the entire image into memory, and (b) the input transformations
|
|---|
| 1240 | you want to do are limited to the following set:
|
|---|
| 1241 |
|
|---|
| 1242 | PNG_TRANSFORM_IDENTITY No transformation
|
|---|
| 1243 | PNG_TRANSFORM_STRIP_16 Strip 16-bit samples to
|
|---|
| 1244 | 8 bits
|
|---|
| 1245 | PNG_TRANSFORM_STRIP_ALPHA Discard the alpha channel
|
|---|
| 1246 | PNG_TRANSFORM_PACKING Expand 1, 2 and 4-bit
|
|---|
| 1247 | samples to bytes
|
|---|
| 1248 | PNG_TRANSFORM_PACKSWAP Change order of packed
|
|---|
| 1249 | pixels to LSB first
|
|---|
| 1250 | PNG_TRANSFORM_EXPAND Perform set_expand()
|
|---|
| 1251 | PNG_TRANSFORM_INVERT_MONO Invert monochrome images
|
|---|
| 1252 | PNG_TRANSFORM_SHIFT Normalize pixels to the
|
|---|
| 1253 | sBIT depth
|
|---|
| 1254 | PNG_TRANSFORM_BGR Flip RGB to BGR, RGBA
|
|---|
| 1255 | to BGRA
|
|---|
| 1256 | PNG_TRANSFORM_SWAP_ALPHA Flip RGBA to ARGB or GA
|
|---|
| 1257 | to AG
|
|---|
| 1258 | PNG_TRANSFORM_INVERT_ALPHA Change alpha from opacity
|
|---|
| 1259 | to transparency
|
|---|
| 1260 | PNG_TRANSFORM_SWAP_ENDIAN Byte-swap 16-bit samples
|
|---|
| 1261 |
|
|---|
| 1262 | (This excludes setting a background color, doing gamma transformation,
|
|---|
| 1263 | dithering, and setting filler.) If this is the case, simply do this:
|
|---|
| 1264 |
|
|---|
| 1265 | png_read_png(png_ptr, info_ptr, png_transforms, NULL)
|
|---|
| 1266 |
|
|---|
| 1267 | where png_transforms is an integer containing the bitwise OR of
|
|---|
| 1268 | some set of transformation flags. This call is equivalent to png_read_info(),
|
|---|
| 1269 | followed the set of transformations indicated by the transform mask,
|
|---|
| 1270 | then png_read_image(), and finally png_read_end().
|
|---|
| 1271 |
|
|---|
| 1272 | (The final parameter of this call is not yet used. Someday it might point
|
|---|
| 1273 | to transformation parameters required by some future input transform.)
|
|---|
| 1274 |
|
|---|
| 1275 | You must use png_transforms and not call any png_set_transform() functions
|
|---|
| 1276 | when you use png_read_png().
|
|---|
| 1277 |
|
|---|
| 1278 | After you have called png_read_png(), you can retrieve the image data
|
|---|
| 1279 | with
|
|---|
| 1280 |
|
|---|
| 1281 | row_pointers = png_get_rows(png_ptr, info_ptr);
|
|---|
| 1282 |
|
|---|
| 1283 | where row_pointers is an array of pointers to the pixel data for each row:
|
|---|
| 1284 |
|
|---|
| 1285 | png_bytep row_pointers[height];
|
|---|
| 1286 |
|
|---|
| 1287 | If you know your image size and pixel size ahead of time, you can allocate
|
|---|
| 1288 | row_pointers prior to calling png_read_png() with
|
|---|
| 1289 |
|
|---|
| 1290 | if (height > PNG_UINT_32_MAX/png_sizeof(png_byte))
|
|---|
| 1291 | png_error (png_ptr,
|
|---|
| 1292 | "Image is too tall to process in memory");
|
|---|
| 1293 | if (width > PNG_UINT_32_MAX/pixel_size)
|
|---|
| 1294 | png_error (png_ptr,
|
|---|
| 1295 | "Image is too wide to process in memory");
|
|---|
| 1296 | row_pointers = png_malloc(png_ptr,
|
|---|
| 1297 | height*png_sizeof(png_bytep));
|
|---|
| 1298 | for (int i=0; i<height, i++)
|
|---|
| 1299 | row_pointers[i]=NULL; /* security precaution */
|
|---|
| 1300 | for (int i=0; i<height, i++)
|
|---|
| 1301 | row_pointers[i]=png_malloc(png_ptr,
|
|---|
| 1302 | width*pixel_size);
|
|---|
| 1303 | png_set_rows(png_ptr, info_ptr, &row_pointers);
|
|---|
| 1304 |
|
|---|
| 1305 | Alternatively you could allocate your image in one big block and define
|
|---|
| 1306 | row_pointers[i] to point into the proper places in your block.
|
|---|
| 1307 |
|
|---|
| 1308 | If you use png_set_rows(), the application is responsible for freeing
|
|---|
| 1309 | row_pointers (and row_pointers[i], if they were separately allocated).
|
|---|
| 1310 |
|
|---|
| 1311 | If you don't allocate row_pointers ahead of time, png_read_png() will
|
|---|
| 1312 | do it, and it'll be free'ed when you call png_destroy_*().
|
|---|
| 1313 |
|
|---|
| 1314 | .SS The low-level read interface
|
|---|
| 1315 |
|
|---|
| 1316 | If you are going the low-level route, you are now ready to read all
|
|---|
| 1317 | the file information up to the actual image data. You do this with a
|
|---|
| 1318 | call to png_read_info().
|
|---|
| 1319 |
|
|---|
| 1320 | png_read_info(png_ptr, info_ptr);
|
|---|
| 1321 |
|
|---|
| 1322 | This will process all chunks up to but not including the image data.
|
|---|
| 1323 |
|
|---|
| 1324 | .SS Querying the info structure
|
|---|
| 1325 |
|
|---|
| 1326 | Functions are used to get the information from the info_ptr once it
|
|---|
| 1327 | has been read. Note that these fields may not be completely filled
|
|---|
| 1328 | in until png_read_end() has read the chunk data following the image.
|
|---|
| 1329 |
|
|---|
| 1330 | png_get_IHDR(png_ptr, info_ptr, &width, &height,
|
|---|
| 1331 | &bit_depth, &color_type, &interlace_type,
|
|---|
| 1332 | &compression_type, &filter_method);
|
|---|
| 1333 |
|
|---|
| 1334 | width - holds the width of the image
|
|---|
| 1335 | in pixels (up to 2^31).
|
|---|
| 1336 | height - holds the height of the image
|
|---|
| 1337 | in pixels (up to 2^31).
|
|---|
| 1338 | bit_depth - holds the bit depth of one of the
|
|---|
| 1339 | image channels. (valid values are
|
|---|
| 1340 | 1, 2, 4, 8, 16 and depend also on
|
|---|
| 1341 | the color_type. See also
|
|---|
| 1342 | significant bits (sBIT) below).
|
|---|
| 1343 | color_type - describes which color/alpha channels
|
|---|
| 1344 | are present.
|
|---|
| 1345 | PNG_COLOR_TYPE_GRAY
|
|---|
| 1346 | (bit depths 1, 2, 4, 8, 16)
|
|---|
| 1347 | PNG_COLOR_TYPE_GRAY_ALPHA
|
|---|
| 1348 | (bit depths 8, 16)
|
|---|
| 1349 | PNG_COLOR_TYPE_PALETTE
|
|---|
| 1350 | (bit depths 1, 2, 4, 8)
|
|---|
| 1351 | PNG_COLOR_TYPE_RGB
|
|---|
| 1352 | (bit_depths 8, 16)
|
|---|
| 1353 | PNG_COLOR_TYPE_RGB_ALPHA
|
|---|
| 1354 | (bit_depths 8, 16)
|
|---|
| 1355 |
|
|---|
| 1356 | PNG_COLOR_MASK_PALETTE
|
|---|
| 1357 | PNG_COLOR_MASK_COLOR
|
|---|
| 1358 | PNG_COLOR_MASK_ALPHA
|
|---|
| 1359 |
|
|---|
| 1360 | filter_method - (must be PNG_FILTER_TYPE_BASE
|
|---|
| 1361 | for PNG 1.0, and can also be
|
|---|
| 1362 | PNG_INTRAPIXEL_DIFFERENCING if
|
|---|
| 1363 | the PNG datastream is embedded in
|
|---|
| 1364 | a MNG-1.0 datastream)
|
|---|
| 1365 | compression_type - (must be PNG_COMPRESSION_TYPE_BASE
|
|---|
| 1366 | for PNG 1.0)
|
|---|
| 1367 | interlace_type - (PNG_INTERLACE_NONE or
|
|---|
| 1368 | PNG_INTERLACE_ADAM7)
|
|---|
| 1369 | Any or all of interlace_type, compression_type, of
|
|---|
| 1370 | filter_method can be NULL if you are
|
|---|
| 1371 | not interested in their values.
|
|---|
| 1372 |
|
|---|
| 1373 | channels = png_get_channels(png_ptr, info_ptr);
|
|---|
| 1374 | channels - number of channels of info for the
|
|---|
| 1375 | color type (valid values are 1 (GRAY,
|
|---|
| 1376 | PALETTE), 2 (GRAY_ALPHA), 3 (RGB),
|
|---|
| 1377 | 4 (RGB_ALPHA or RGB + filler byte))
|
|---|
| 1378 | rowbytes = png_get_rowbytes(png_ptr, info_ptr);
|
|---|
| 1379 | rowbytes - number of bytes needed to hold a row
|
|---|
| 1380 |
|
|---|
| 1381 | signature = png_get_signature(png_ptr, info_ptr);
|
|---|
| 1382 | signature - holds the signature read from the
|
|---|
| 1383 | file (if any). The data is kept in
|
|---|
| 1384 | the same offset it would be if the
|
|---|
| 1385 | whole signature were read (i.e. if an
|
|---|
| 1386 | application had already read in 4
|
|---|
| 1387 | bytes of signature before starting
|
|---|
| 1388 | libpng, the remaining 4 bytes would
|
|---|
| 1389 | be in signature[4] through signature[7]
|
|---|
| 1390 | (see png_set_sig_bytes())).
|
|---|
| 1391 |
|
|---|
| 1392 |
|
|---|
| 1393 | width = png_get_image_width(png_ptr,
|
|---|
| 1394 | info_ptr);
|
|---|
| 1395 | height = png_get_image_height(png_ptr,
|
|---|
| 1396 | info_ptr);
|
|---|
| 1397 | bit_depth = png_get_bit_depth(png_ptr,
|
|---|
| 1398 | info_ptr);
|
|---|
| 1399 | color_type = png_get_color_type(png_ptr,
|
|---|
| 1400 | info_ptr);
|
|---|
| 1401 | filter_method = png_get_filter_type(png_ptr,
|
|---|
| 1402 | info_ptr);
|
|---|
| 1403 | compression_type = png_get_compression_type(png_ptr,
|
|---|
| 1404 | info_ptr);
|
|---|
| 1405 | interlace_type = png_get_interlace_type(png_ptr,
|
|---|
| 1406 | info_ptr);
|
|---|
| 1407 |
|
|---|
| 1408 |
|
|---|
| 1409 | These are also important, but their validity depends on whether the chunk
|
|---|
| 1410 | has been read. The png_get_valid(png_ptr, info_ptr, PNG_INFO_<chunk>) and
|
|---|
| 1411 | png_get_<chunk>(png_ptr, info_ptr, ...) functions return non-zero if the
|
|---|
| 1412 | data has been read, or zero if it is missing. The parameters to the
|
|---|
| 1413 | png_get_<chunk> are set directly if they are simple data types, or a pointer
|
|---|
| 1414 | into the info_ptr is returned for any complex types.
|
|---|
| 1415 |
|
|---|
| 1416 | png_get_PLTE(png_ptr, info_ptr, &palette,
|
|---|
| 1417 | &num_palette);
|
|---|
| 1418 | palette - the palette for the file
|
|---|
| 1419 | (array of png_color)
|
|---|
| 1420 | num_palette - number of entries in the palette
|
|---|
| 1421 |
|
|---|
| 1422 | png_get_gAMA(png_ptr, info_ptr, &gamma);
|
|---|
| 1423 | gamma - the gamma the file is written
|
|---|
| 1424 | at (PNG_INFO_gAMA)
|
|---|
| 1425 |
|
|---|
| 1426 | png_get_sRGB(png_ptr, info_ptr, &srgb_intent);
|
|---|
| 1427 | srgb_intent - the rendering intent (PNG_INFO_sRGB)
|
|---|
| 1428 | The presence of the sRGB chunk
|
|---|
| 1429 | means that the pixel data is in the
|
|---|
| 1430 | sRGB color space. This chunk also
|
|---|
| 1431 | implies specific values of gAMA and
|
|---|
| 1432 | cHRM.
|
|---|
| 1433 |
|
|---|
| 1434 | png_get_iCCP(png_ptr, info_ptr, &name,
|
|---|
| 1435 | &compression_type, &profile, &proflen);
|
|---|
| 1436 | name - The profile name.
|
|---|
| 1437 | compression - The compression type; always
|
|---|
| 1438 | PNG_COMPRESSION_TYPE_BASE for PNG 1.0.
|
|---|
| 1439 | You may give NULL to this argument to
|
|---|
| 1440 | ignore it.
|
|---|
| 1441 | profile - International Color Consortium color
|
|---|
| 1442 | profile data. May contain NULs.
|
|---|
| 1443 | proflen - length of profile data in bytes.
|
|---|
| 1444 |
|
|---|
| 1445 | png_get_sBIT(png_ptr, info_ptr, &sig_bit);
|
|---|
| 1446 | sig_bit - the number of significant bits for
|
|---|
| 1447 | (PNG_INFO_sBIT) each of the gray,
|
|---|
| 1448 | red, green, and blue channels,
|
|---|
| 1449 | whichever are appropriate for the
|
|---|
| 1450 | given color type (png_color_16)
|
|---|
| 1451 |
|
|---|
| 1452 | png_get_tRNS(png_ptr, info_ptr, &trans, &num_trans,
|
|---|
| 1453 | &trans_values);
|
|---|
| 1454 | trans - array of transparent entries for
|
|---|
| 1455 | palette (PNG_INFO_tRNS)
|
|---|
| 1456 | trans_values - graylevel or color sample values of
|
|---|
| 1457 | the single transparent color for
|
|---|
| 1458 | non-paletted images (PNG_INFO_tRNS)
|
|---|
| 1459 | num_trans - number of transparent entries
|
|---|
| 1460 | (PNG_INFO_tRNS)
|
|---|
| 1461 |
|
|---|
| 1462 | png_get_hIST(png_ptr, info_ptr, &hist);
|
|---|
| 1463 | (PNG_INFO_hIST)
|
|---|
| 1464 | hist - histogram of palette (array of
|
|---|
| 1465 | png_uint_16)
|
|---|
| 1466 |
|
|---|
| 1467 | png_get_tIME(png_ptr, info_ptr, &mod_time);
|
|---|
| 1468 | mod_time - time image was last modified
|
|---|
| 1469 | (PNG_VALID_tIME)
|
|---|
| 1470 |
|
|---|
| 1471 | png_get_bKGD(png_ptr, info_ptr, &background);
|
|---|
| 1472 | background - background color (PNG_VALID_bKGD)
|
|---|
| 1473 | valid 16-bit red, green and blue
|
|---|
| 1474 | values, regardless of color_type
|
|---|
| 1475 |
|
|---|
| 1476 | num_comments = png_get_text(png_ptr, info_ptr,
|
|---|
| 1477 | &text_ptr, &num_text);
|
|---|
| 1478 | num_comments - number of comments
|
|---|
| 1479 | text_ptr - array of png_text holding image
|
|---|
| 1480 | comments
|
|---|
| 1481 | text_ptr[i].compression - type of compression used
|
|---|
| 1482 | on "text" PNG_TEXT_COMPRESSION_NONE
|
|---|
| 1483 | PNG_TEXT_COMPRESSION_zTXt
|
|---|
| 1484 | PNG_ITXT_COMPRESSION_NONE
|
|---|
| 1485 | PNG_ITXT_COMPRESSION_zTXt
|
|---|
| 1486 | text_ptr[i].key - keyword for comment. Must contain
|
|---|
| 1487 | 1-79 characters.
|
|---|
| 1488 | text_ptr[i].text - text comments for current
|
|---|
| 1489 | keyword. Can be empty.
|
|---|
| 1490 | text_ptr[i].text_length - length of text string,
|
|---|
| 1491 | after decompression, 0 for iTXt
|
|---|
| 1492 | text_ptr[i].itxt_length - length of itxt string,
|
|---|
| 1493 | after decompression, 0 for tEXt/zTXt
|
|---|
| 1494 | text_ptr[i].lang - language of comment (empty
|
|---|
| 1495 | string for unknown).
|
|---|
| 1496 | text_ptr[i].lang_key - keyword in UTF-8
|
|---|
| 1497 | (empty string for unknown).
|
|---|
| 1498 | num_text - number of comments (same as
|
|---|
| 1499 | num_comments; you can put NULL here
|
|---|
| 1500 | to avoid the duplication)
|
|---|
| 1501 | Note while png_set_text() will accept text, language,
|
|---|
| 1502 | and translated keywords that can be NULL pointers, the
|
|---|
| 1503 | structure returned by png_get_text will always contain
|
|---|
| 1504 | regular zero-terminated C strings. They might be
|
|---|
| 1505 | empty strings but they will never be NULL pointers.
|
|---|
| 1506 |
|
|---|
| 1507 | num_spalettes = png_get_sPLT(png_ptr, info_ptr,
|
|---|
| 1508 | &palette_ptr);
|
|---|
| 1509 | palette_ptr - array of palette structures holding
|
|---|
| 1510 | contents of one or more sPLT chunks
|
|---|
| 1511 | read.
|
|---|
| 1512 | num_spalettes - number of sPLT chunks read.
|
|---|
| 1513 |
|
|---|
| 1514 | png_get_oFFs(png_ptr, info_ptr, &offset_x, &offset_y,
|
|---|
| 1515 | &unit_type);
|
|---|
| 1516 | offset_x - positive offset from the left edge
|
|---|
| 1517 | of the screen
|
|---|
| 1518 | offset_y - positive offset from the top edge
|
|---|
| 1519 | of the screen
|
|---|
| 1520 | unit_type - PNG_OFFSET_PIXEL, PNG_OFFSET_MICROMETER
|
|---|
| 1521 |
|
|---|
| 1522 | png_get_pHYs(png_ptr, info_ptr, &res_x, &res_y,
|
|---|
| 1523 | &unit_type);
|
|---|
| 1524 | res_x - pixels/unit physical resolution in
|
|---|
| 1525 | x direction
|
|---|
| 1526 | res_y - pixels/unit physical resolution in
|
|---|
| 1527 | x direction
|
|---|
| 1528 | unit_type - PNG_RESOLUTION_UNKNOWN,
|
|---|
| 1529 | PNG_RESOLUTION_METER
|
|---|
| 1530 |
|
|---|
| 1531 | png_get_sCAL(png_ptr, info_ptr, &unit, &width,
|
|---|
| 1532 | &height)
|
|---|
| 1533 | unit - physical scale units (an integer)
|
|---|
| 1534 | width - width of a pixel in physical scale units
|
|---|
| 1535 | height - height of a pixel in physical scale units
|
|---|
| 1536 | (width and height are doubles)
|
|---|
| 1537 |
|
|---|
| 1538 | png_get_sCAL_s(png_ptr, info_ptr, &unit, &width,
|
|---|
| 1539 | &height)
|
|---|
| 1540 | unit - physical scale units (an integer)
|
|---|
| 1541 | width - width of a pixel in physical scale units
|
|---|
| 1542 | height - height of a pixel in physical scale units
|
|---|
| 1543 | (width and height are strings like "2.54")
|
|---|
| 1544 |
|
|---|
| 1545 | num_unknown_chunks = png_get_unknown_chunks(png_ptr,
|
|---|
| 1546 | info_ptr, &unknowns)
|
|---|
| 1547 | unknowns - array of png_unknown_chunk
|
|---|
| 1548 | structures holding unknown chunks
|
|---|
| 1549 | unknowns[i].name - name of unknown chunk
|
|---|
| 1550 | unknowns[i].data - data of unknown chunk
|
|---|
| 1551 | unknowns[i].size - size of unknown chunk's data
|
|---|
| 1552 | unknowns[i].location - position of chunk in file
|
|---|
| 1553 |
|
|---|
| 1554 | The value of "i" corresponds to the order in which the
|
|---|
| 1555 | chunks were read from the PNG file or inserted with the
|
|---|
| 1556 | png_set_unknown_chunks() function.
|
|---|
| 1557 |
|
|---|
| 1558 | The data from the pHYs chunk can be retrieved in several convenient
|
|---|
| 1559 | forms:
|
|---|
| 1560 |
|
|---|
| 1561 | res_x = png_get_x_pixels_per_meter(png_ptr,
|
|---|
| 1562 | info_ptr)
|
|---|
| 1563 | res_y = png_get_y_pixels_per_meter(png_ptr,
|
|---|
| 1564 | info_ptr)
|
|---|
| 1565 | res_x_and_y = png_get_pixels_per_meter(png_ptr,
|
|---|
| 1566 | info_ptr)
|
|---|
| 1567 | res_x = png_get_x_pixels_per_inch(png_ptr,
|
|---|
| 1568 | info_ptr)
|
|---|
| 1569 | res_y = png_get_y_pixels_per_inch(png_ptr,
|
|---|
| 1570 | info_ptr)
|
|---|
| 1571 | res_x_and_y = png_get_pixels_per_inch(png_ptr,
|
|---|
| 1572 | info_ptr)
|
|---|
| 1573 | aspect_ratio = png_get_pixel_aspect_ratio(png_ptr,
|
|---|
| 1574 | info_ptr)
|
|---|
| 1575 |
|
|---|
| 1576 | (Each of these returns 0 [signifying "unknown"] if
|
|---|
| 1577 | the data is not present or if res_x is 0;
|
|---|
| 1578 | res_x_and_y is 0 if res_x != res_y)
|
|---|
| 1579 |
|
|---|
| 1580 | The data from the oFFs chunk can be retrieved in several convenient
|
|---|
| 1581 | forms:
|
|---|
| 1582 |
|
|---|
| 1583 | x_offset = png_get_x_offset_microns(png_ptr, info_ptr);
|
|---|
| 1584 | y_offset = png_get_y_offset_microns(png_ptr, info_ptr);
|
|---|
| 1585 | x_offset = png_get_x_offset_inches(png_ptr, info_ptr);
|
|---|
| 1586 | y_offset = png_get_y_offset_inches(png_ptr, info_ptr);
|
|---|
| 1587 |
|
|---|
| 1588 | (Each of these returns 0 [signifying "unknown" if both
|
|---|
| 1589 | x and y are 0] if the data is not present or if the
|
|---|
| 1590 | chunk is present but the unit is the pixel)
|
|---|
| 1591 |
|
|---|
| 1592 | For more information, see the png_info definition in png.h and the
|
|---|
| 1593 | PNG specification for chunk contents. Be careful with trusting
|
|---|
| 1594 | rowbytes, as some of the transformations could increase the space
|
|---|
| 1595 | needed to hold a row (expand, filler, gray_to_rgb, etc.).
|
|---|
| 1596 | See png_read_update_info(), below.
|
|---|
| 1597 |
|
|---|
| 1598 | A quick word about text_ptr and num_text. PNG stores comments in
|
|---|
| 1599 | keyword/text pairs, one pair per chunk, with no limit on the number
|
|---|
| 1600 | of text chunks, and a 2^31 byte limit on their size. While there are
|
|---|
| 1601 | suggested keywords, there is no requirement to restrict the use to these
|
|---|
| 1602 | strings. It is strongly suggested that keywords and text be sensible
|
|---|
| 1603 | to humans (that's the point), so don't use abbreviations. Non-printing
|
|---|
| 1604 | symbols are not allowed. See the PNG specification for more details.
|
|---|
| 1605 | There is also no requirement to have text after the keyword.
|
|---|
| 1606 |
|
|---|
| 1607 | Keywords should be limited to 79 Latin-1 characters without leading or
|
|---|
| 1608 | trailing spaces, but non-consecutive spaces are allowed within the
|
|---|
| 1609 | keyword. It is possible to have the same keyword any number of times.
|
|---|
| 1610 | The text_ptr is an array of png_text structures, each holding a
|
|---|
| 1611 | pointer to a language string, a pointer to a keyword and a pointer to
|
|---|
| 1612 | a text string. The text string, language code, and translated
|
|---|
| 1613 | keyword may be empty or NULL pointers. The keyword/text
|
|---|
| 1614 | pairs are put into the array in the order that they are received.
|
|---|
| 1615 | However, some or all of the text chunks may be after the image, so, to
|
|---|
| 1616 | make sure you have read all the text chunks, don't mess with these
|
|---|
| 1617 | until after you read the stuff after the image. This will be
|
|---|
| 1618 | mentioned again below in the discussion that goes with png_read_end().
|
|---|
| 1619 |
|
|---|
| 1620 | .SS Input transformations
|
|---|
| 1621 |
|
|---|
| 1622 | After you've read the header information, you can set up the library
|
|---|
| 1623 | to handle any special transformations of the image data. The various
|
|---|
| 1624 | ways to transform the data will be described in the order that they
|
|---|
| 1625 | should occur. This is important, as some of these change the color
|
|---|
| 1626 | type and/or bit depth of the data, and some others only work on
|
|---|
| 1627 | certain color types and bit depths. Even though each transformation
|
|---|
| 1628 | checks to see if it has data that it can do something with, you should
|
|---|
| 1629 | make sure to only enable a transformation if it will be valid for the
|
|---|
| 1630 | data. For example, don't swap red and blue on grayscale data.
|
|---|
| 1631 |
|
|---|
| 1632 | The colors used for the background and transparency values should be
|
|---|
| 1633 | supplied in the same format/depth as the current image data. They
|
|---|
| 1634 | are stored in the same format/depth as the image data in a bKGD or tRNS
|
|---|
| 1635 | chunk, so this is what libpng expects for this data. The colors are
|
|---|
| 1636 | transformed to keep in sync with the image data when an application
|
|---|
| 1637 | calls the png_read_update_info() routine (see below).
|
|---|
| 1638 |
|
|---|
| 1639 | Data will be decoded into the supplied row buffers packed into bytes
|
|---|
| 1640 | unless the library has been told to transform it into another format.
|
|---|
| 1641 | For example, 4 bit/pixel paletted or grayscale data will be returned
|
|---|
| 1642 | 2 pixels/byte with the leftmost pixel in the high-order bits of the
|
|---|
| 1643 | byte, unless png_set_packing() is called. 8-bit RGB data will be stored
|
|---|
| 1644 | in RGB RGB RGB format unless png_set_filler() or png_set_add_alpha()
|
|---|
| 1645 | is called to insert filler bytes, either before or after each RGB triplet.
|
|---|
| 1646 | 16-bit RGB data will be returned RRGGBB RRGGBB, with the most significant
|
|---|
| 1647 | byte of the color value first, unless png_set_strip_16() is called to
|
|---|
| 1648 | transform it to regular RGB RGB triplets, or png_set_filler() or
|
|---|
| 1649 | png_set_add alpha() is called to insert filler bytes, either before or
|
|---|
| 1650 | after each RRGGBB triplet. Similarly, 8-bit or 16-bit grayscale data can
|
|---|
| 1651 | be modified with
|
|---|
| 1652 | png_set_filler(), png_set_add_alpha(), or png_set_strip_16().
|
|---|
| 1653 |
|
|---|
| 1654 | The following code transforms grayscale images of less than 8 to 8 bits,
|
|---|
| 1655 | changes paletted images to RGB, and adds a full alpha channel if there is
|
|---|
| 1656 | transparency information in a tRNS chunk. This is most useful on
|
|---|
| 1657 | grayscale images with bit depths of 2 or 4 or if there is a multiple-image
|
|---|
| 1658 | viewing application that wishes to treat all images in the same way.
|
|---|
| 1659 |
|
|---|
| 1660 | if (color_type == PNG_COLOR_TYPE_PALETTE)
|
|---|
| 1661 | png_set_palette_to_rgb(png_ptr);
|
|---|
| 1662 |
|
|---|
| 1663 | if (color_type == PNG_COLOR_TYPE_GRAY &&
|
|---|
| 1664 | bit_depth < 8) png_set_expand_gray_1_2_4_to_8(png_ptr);
|
|---|
| 1665 |
|
|---|
| 1666 | if (png_get_valid(png_ptr, info_ptr,
|
|---|
| 1667 | PNG_INFO_tRNS)) png_set_tRNS_to_alpha(png_ptr);
|
|---|
| 1668 |
|
|---|
| 1669 | These three functions are actually aliases for png_set_expand(), added
|
|---|
| 1670 | in libpng version 1.0.4, with the function names expanded to improve code
|
|---|
| 1671 | readability. In some future version they may actually do different
|
|---|
| 1672 | things.
|
|---|
| 1673 |
|
|---|
| 1674 | As of libpng version 1.2.9, png_set_expand_gray_1_2_4_to_8() was
|
|---|
| 1675 | added. It expands the sample depth without changing tRNS to alpha.
|
|---|
| 1676 |
|
|---|
| 1677 | PNG can have files with 16 bits per channel. If you only can handle
|
|---|
| 1678 | 8 bits per channel, this will strip the pixels down to 8 bit.
|
|---|
| 1679 |
|
|---|
| 1680 | if (bit_depth == 16)
|
|---|
| 1681 | png_set_strip_16(png_ptr);
|
|---|
| 1682 |
|
|---|
| 1683 | If, for some reason, you don't need the alpha channel on an image,
|
|---|
| 1684 | and you want to remove it rather than combining it with the background
|
|---|
| 1685 | (but the image author certainly had in mind that you *would* combine
|
|---|
| 1686 | it with the background, so that's what you should probably do):
|
|---|
| 1687 |
|
|---|
| 1688 | if (color_type & PNG_COLOR_MASK_ALPHA)
|
|---|
| 1689 | png_set_strip_alpha(png_ptr);
|
|---|
| 1690 |
|
|---|
| 1691 | In PNG files, the alpha channel in an image
|
|---|
| 1692 | is the level of opacity. If you need the alpha channel in an image to
|
|---|
| 1693 | be the level of transparency instead of opacity, you can invert the
|
|---|
| 1694 | alpha channel (or the tRNS chunk data) after it's read, so that 0 is
|
|---|
| 1695 | fully opaque and 255 (in 8-bit or paletted images) or 65535 (in 16-bit
|
|---|
| 1696 | images) is fully transparent, with
|
|---|
| 1697 |
|
|---|
| 1698 | png_set_invert_alpha(png_ptr);
|
|---|
| 1699 |
|
|---|
| 1700 | PNG files pack pixels of bit depths 1, 2, and 4 into bytes as small as
|
|---|
| 1701 | they can, resulting in, for example, 8 pixels per byte for 1 bit
|
|---|
| 1702 | files. This code expands to 1 pixel per byte without changing the
|
|---|
| 1703 | values of the pixels:
|
|---|
| 1704 |
|
|---|
| 1705 | if (bit_depth < 8)
|
|---|
| 1706 | png_set_packing(png_ptr);
|
|---|
| 1707 |
|
|---|
| 1708 | PNG files have possible bit depths of 1, 2, 4, 8, and 16. All pixels
|
|---|
| 1709 | stored in a PNG image have been "scaled" or "shifted" up to the next
|
|---|
| 1710 | higher possible bit depth (e.g. from 5 bits/sample in the range [0,31] to
|
|---|
| 1711 | 8 bits/sample in the range [0, 255]). However, it is also possible to
|
|---|
| 1712 | convert the PNG pixel data back to the original bit depth of the image.
|
|---|
| 1713 | This call reduces the pixels back down to the original bit depth:
|
|---|
| 1714 |
|
|---|
| 1715 | png_color_8p sig_bit;
|
|---|
| 1716 |
|
|---|
| 1717 | if (png_get_sBIT(png_ptr, info_ptr, &sig_bit))
|
|---|
| 1718 | png_set_shift(png_ptr, sig_bit);
|
|---|
| 1719 |
|
|---|
| 1720 | PNG files store 3-color pixels in red, green, blue order. This code
|
|---|
| 1721 | changes the storage of the pixels to blue, green, red:
|
|---|
| 1722 |
|
|---|
| 1723 | if (color_type == PNG_COLOR_TYPE_RGB ||
|
|---|
| 1724 | color_type == PNG_COLOR_TYPE_RGB_ALPHA)
|
|---|
| 1725 | png_set_bgr(png_ptr);
|
|---|
| 1726 |
|
|---|
| 1727 | PNG files store RGB pixels packed into 3 or 6 bytes. This code expands them
|
|---|
| 1728 | into 4 or 8 bytes for windowing systems that need them in this format:
|
|---|
| 1729 |
|
|---|
| 1730 | if (color_type == PNG_COLOR_TYPE_RGB)
|
|---|
| 1731 | png_set_filler(png_ptr, filler, PNG_FILLER_BEFORE);
|
|---|
| 1732 |
|
|---|
| 1733 | where "filler" is the 8 or 16-bit number to fill with, and the location is
|
|---|
| 1734 | either PNG_FILLER_BEFORE or PNG_FILLER_AFTER, depending upon whether
|
|---|
| 1735 | you want the filler before the RGB or after. This transformation
|
|---|
| 1736 | does not affect images that already have full alpha channels. To add an
|
|---|
| 1737 | opaque alpha channel, use filler=0xff or 0xffff and PNG_FILLER_AFTER which
|
|---|
| 1738 | will generate RGBA pixels.
|
|---|
| 1739 |
|
|---|
| 1740 | Note that png_set_filler() does not change the color type. If you want
|
|---|
| 1741 | to do that, you can add a true alpha channel with
|
|---|
| 1742 |
|
|---|
| 1743 | if (color_type == PNG_COLOR_TYPE_RGB ||
|
|---|
| 1744 | color_type == PNG_COLOR_TYPE_GRAY)
|
|---|
| 1745 | png_set_add_alpha(png_ptr, filler, PNG_FILLER_AFTER);
|
|---|
| 1746 |
|
|---|
| 1747 | where "filler" contains the alpha value to assign to each pixel.
|
|---|
| 1748 | This function was added in libpng-1.2.7.
|
|---|
| 1749 |
|
|---|
| 1750 | If you are reading an image with an alpha channel, and you need the
|
|---|
| 1751 | data as ARGB instead of the normal PNG format RGBA:
|
|---|
| 1752 |
|
|---|
| 1753 | if (color_type == PNG_COLOR_TYPE_RGB_ALPHA)
|
|---|
| 1754 | png_set_swap_alpha(png_ptr);
|
|---|
| 1755 |
|
|---|
| 1756 | For some uses, you may want a grayscale image to be represented as
|
|---|
| 1757 | RGB. This code will do that conversion:
|
|---|
| 1758 |
|
|---|
| 1759 | if (color_type == PNG_COLOR_TYPE_GRAY ||
|
|---|
| 1760 | color_type == PNG_COLOR_TYPE_GRAY_ALPHA)
|
|---|
| 1761 | png_set_gray_to_rgb(png_ptr);
|
|---|
| 1762 |
|
|---|
| 1763 | Conversely, you can convert an RGB or RGBA image to grayscale or grayscale
|
|---|
| 1764 | with alpha.
|
|---|
| 1765 |
|
|---|
| 1766 | if (color_type == PNG_COLOR_TYPE_RGB ||
|
|---|
| 1767 | color_type == PNG_COLOR_TYPE_RGB_ALPHA)
|
|---|
| 1768 | png_set_rgb_to_gray_fixed(png_ptr, error_action,
|
|---|
| 1769 | int red_weight, int green_weight);
|
|---|
| 1770 |
|
|---|
| 1771 | error_action = 1: silently do the conversion
|
|---|
| 1772 | error_action = 2: issue a warning if the original
|
|---|
| 1773 | image has any pixel where
|
|---|
| 1774 | red != green or red != blue
|
|---|
| 1775 | error_action = 3: issue an error and abort the
|
|---|
| 1776 | conversion if the original
|
|---|
| 1777 | image has any pixel where
|
|---|
| 1778 | red != green or red != blue
|
|---|
| 1779 |
|
|---|
| 1780 | red_weight: weight of red component times 100000
|
|---|
| 1781 | green_weight: weight of green component times 100000
|
|---|
| 1782 | If either weight is negative, default
|
|---|
| 1783 | weights (21268, 71514) are used.
|
|---|
| 1784 |
|
|---|
| 1785 | If you have set error_action = 1 or 2, you can
|
|---|
| 1786 | later check whether the image really was gray, after processing
|
|---|
| 1787 | the image rows, with the png_get_rgb_to_gray_status(png_ptr) function.
|
|---|
| 1788 | It will return a png_byte that is zero if the image was gray or
|
|---|
| 1789 | 1 if there were any non-gray pixels. bKGD and sBIT data
|
|---|
| 1790 | will be silently converted to grayscale, using the green channel
|
|---|
| 1791 | data, regardless of the error_action setting.
|
|---|
| 1792 |
|
|---|
| 1793 | With red_weight+green_weight<=100000,
|
|---|
| 1794 | the normalized graylevel is computed:
|
|---|
| 1795 |
|
|---|
| 1796 | int rw = red_weight * 65536;
|
|---|
| 1797 | int gw = green_weight * 65536;
|
|---|
| 1798 | int bw = 65536 - (rw + gw);
|
|---|
| 1799 | gray = (rw*red + gw*green + bw*blue)/65536;
|
|---|
| 1800 |
|
|---|
| 1801 | The default values approximate those recommended in the Charles
|
|---|
| 1802 | Poynton's Color FAQ, <http://www.inforamp.net/~poynton/>
|
|---|
| 1803 | Copyright (c) 1998-01-04 Charles Poynton <poynton at inforamp.net>
|
|---|
| 1804 |
|
|---|
| 1805 | Y = 0.212671 * R + 0.715160 * G + 0.072169 * B
|
|---|
| 1806 |
|
|---|
| 1807 | Libpng approximates this with
|
|---|
| 1808 |
|
|---|
| 1809 | Y = 0.21268 * R + 0.7151 * G + 0.07217 * B
|
|---|
| 1810 |
|
|---|
| 1811 | which can be expressed with integers as
|
|---|
| 1812 |
|
|---|
| 1813 | Y = (6969 * R + 23434 * G + 2365 * B)/32768
|
|---|
| 1814 |
|
|---|
| 1815 | The calculation is done in a linear colorspace, if the image gamma
|
|---|
| 1816 | is known.
|
|---|
| 1817 |
|
|---|
| 1818 | If you have a grayscale and you are using png_set_expand_depth(),
|
|---|
| 1819 | png_set_expand(), or png_set_gray_to_rgb to change to truecolor or to
|
|---|
| 1820 | a higher bit-depth, you must either supply the background color as a gray
|
|---|
| 1821 | value at the original file bit-depth (need_expand = 1) or else supply the
|
|---|
| 1822 | background color as an RGB triplet at the final, expanded bit depth
|
|---|
| 1823 | (need_expand = 0). Similarly, if you are reading a paletted image, you
|
|---|
| 1824 | must either supply the background color as a palette index (need_expand = 1)
|
|---|
| 1825 | or as an RGB triplet that may or may not be in the palette (need_expand = 0).
|
|---|
| 1826 |
|
|---|
| 1827 | png_color_16 my_background;
|
|---|
| 1828 | png_color_16p image_background;
|
|---|
| 1829 |
|
|---|
| 1830 | if (png_get_bKGD(png_ptr, info_ptr, &image_background))
|
|---|
| 1831 | png_set_background(png_ptr, image_background,
|
|---|
| 1832 | PNG_BACKGROUND_GAMMA_FILE, 1, 1.0);
|
|---|
| 1833 | else
|
|---|
| 1834 | png_set_background(png_ptr, &my_background,
|
|---|
| 1835 | PNG_BACKGROUND_GAMMA_SCREEN, 0, 1.0);
|
|---|
| 1836 |
|
|---|
| 1837 | The png_set_background() function tells libpng to composite images
|
|---|
| 1838 | with alpha or simple transparency against the supplied background
|
|---|
| 1839 | color. If the PNG file contains a bKGD chunk (PNG_INFO_bKGD valid),
|
|---|
| 1840 | you may use this color, or supply another color more suitable for
|
|---|
| 1841 | the current display (e.g., the background color from a web page). You
|
|---|
| 1842 | need to tell libpng whether the color is in the gamma space of the
|
|---|
| 1843 | display (PNG_BACKGROUND_GAMMA_SCREEN for colors you supply), the file
|
|---|
| 1844 | (PNG_BACKGROUND_GAMMA_FILE for colors from the bKGD chunk), or one
|
|---|
| 1845 | that is neither of these gammas (PNG_BACKGROUND_GAMMA_UNIQUE - I don't
|
|---|
| 1846 | know why anyone would use this, but it's here).
|
|---|
| 1847 |
|
|---|
| 1848 | To properly display PNG images on any kind of system, the application needs
|
|---|
| 1849 | to know what the display gamma is. Ideally, the user will know this, and
|
|---|
| 1850 | the application will allow them to set it. One method of allowing the user
|
|---|
| 1851 | to set the display gamma separately for each system is to check for a
|
|---|
| 1852 | SCREEN_GAMMA or DISPLAY_GAMMA environment variable, which will hopefully be
|
|---|
| 1853 | correctly set.
|
|---|
| 1854 |
|
|---|
| 1855 | Note that display_gamma is the overall gamma correction required to produce
|
|---|
| 1856 | pleasing results, which depends on the lighting conditions in the surrounding
|
|---|
| 1857 | environment. In a dim or brightly lit room, no compensation other than
|
|---|
| 1858 | the physical gamma exponent of the monitor is needed, while in a dark room
|
|---|
| 1859 | a slightly smaller exponent is better.
|
|---|
| 1860 |
|
|---|
| 1861 | double gamma, screen_gamma;
|
|---|
| 1862 |
|
|---|
| 1863 | if (/* We have a user-defined screen
|
|---|
| 1864 | gamma value */)
|
|---|
| 1865 | {
|
|---|
| 1866 | screen_gamma = user_defined_screen_gamma;
|
|---|
| 1867 | }
|
|---|
| 1868 | /* One way that applications can share the same
|
|---|
| 1869 | screen gamma value */
|
|---|
| 1870 | else if ((gamma_str = getenv("SCREEN_GAMMA"))
|
|---|
| 1871 | != NULL)
|
|---|
| 1872 | {
|
|---|
| 1873 | screen_gamma = (double)atof(gamma_str);
|
|---|
| 1874 | }
|
|---|
| 1875 | /* If we don't have another value */
|
|---|
| 1876 | else
|
|---|
| 1877 | {
|
|---|
| 1878 | screen_gamma = 2.2; /* A good guess for a
|
|---|
| 1879 | PC monitor in a bright office or a dim room */
|
|---|
| 1880 | screen_gamma = 2.0; /* A good guess for a
|
|---|
| 1881 | PC monitor in a dark room */
|
|---|
| 1882 | screen_gamma = 1.7 or 1.0; /* A good
|
|---|
| 1883 | guess for Mac systems */
|
|---|
| 1884 | }
|
|---|
| 1885 |
|
|---|
| 1886 | The png_set_gamma() function handles gamma transformations of the data.
|
|---|
| 1887 | Pass both the file gamma and the current screen_gamma. If the file does
|
|---|
| 1888 | not have a gamma value, you can pass one anyway if you have an idea what
|
|---|
| 1889 | it is (usually 0.45455 is a good guess for GIF images on PCs). Note
|
|---|
| 1890 | that file gammas are inverted from screen gammas. See the discussions
|
|---|
| 1891 | on gamma in the PNG specification for an excellent description of what
|
|---|
| 1892 | gamma is, and why all applications should support it. It is strongly
|
|---|
| 1893 | recommended that PNG viewers support gamma correction.
|
|---|
| 1894 |
|
|---|
| 1895 | if (png_get_gAMA(png_ptr, info_ptr, &gamma))
|
|---|
| 1896 | png_set_gamma(png_ptr, screen_gamma, gamma);
|
|---|
| 1897 | else
|
|---|
| 1898 | png_set_gamma(png_ptr, screen_gamma, 0.45455);
|
|---|
| 1899 |
|
|---|
| 1900 | If you need to reduce an RGB file to a paletted file, or if a paletted
|
|---|
| 1901 | file has more entries then will fit on your screen, png_set_dither()
|
|---|
| 1902 | will do that. Note that this is a simple match dither that merely
|
|---|
| 1903 | finds the closest color available. This should work fairly well with
|
|---|
| 1904 | optimized palettes, and fairly badly with linear color cubes. If you
|
|---|
| 1905 | pass a palette that is larger then maximum_colors, the file will
|
|---|
| 1906 | reduce the number of colors in the palette so it will fit into
|
|---|
| 1907 | maximum_colors. If there is a histogram, it will use it to make
|
|---|
| 1908 | more intelligent choices when reducing the palette. If there is no
|
|---|
| 1909 | histogram, it may not do as good a job.
|
|---|
| 1910 |
|
|---|
| 1911 | if (color_type & PNG_COLOR_MASK_COLOR)
|
|---|
| 1912 | {
|
|---|
| 1913 | if (png_get_valid(png_ptr, info_ptr,
|
|---|
| 1914 | PNG_INFO_PLTE))
|
|---|
| 1915 | {
|
|---|
| 1916 | png_uint_16p histogram = NULL;
|
|---|
| 1917 |
|
|---|
| 1918 | png_get_hIST(png_ptr, info_ptr,
|
|---|
| 1919 | &histogram);
|
|---|
| 1920 | png_set_dither(png_ptr, palette, num_palette,
|
|---|
| 1921 | max_screen_colors, histogram, 1);
|
|---|
| 1922 | }
|
|---|
| 1923 | else
|
|---|
| 1924 | {
|
|---|
| 1925 | png_color std_color_cube[MAX_SCREEN_COLORS] =
|
|---|
| 1926 | { ... colors ... };
|
|---|
| 1927 |
|
|---|
| 1928 | png_set_dither(png_ptr, std_color_cube,
|
|---|
| 1929 | MAX_SCREEN_COLORS, MAX_SCREEN_COLORS,
|
|---|
| 1930 | NULL,0);
|
|---|
| 1931 | }
|
|---|
| 1932 | }
|
|---|
| 1933 |
|
|---|
| 1934 | PNG files describe monochrome as black being zero and white being one.
|
|---|
| 1935 | The following code will reverse this (make black be one and white be
|
|---|
| 1936 | zero):
|
|---|
| 1937 |
|
|---|
| 1938 | if (bit_depth == 1 && color_type == PNG_COLOR_TYPE_GRAY)
|
|---|
| 1939 | png_set_invert_mono(png_ptr);
|
|---|
| 1940 |
|
|---|
| 1941 | This function can also be used to invert grayscale and gray-alpha images:
|
|---|
| 1942 |
|
|---|
| 1943 | if (color_type == PNG_COLOR_TYPE_GRAY ||
|
|---|
| 1944 | color_type == PNG_COLOR_TYPE_GRAY_ALPHA)
|
|---|
| 1945 | png_set_invert_mono(png_ptr);
|
|---|
| 1946 |
|
|---|
| 1947 | PNG files store 16 bit pixels in network byte order (big-endian,
|
|---|
| 1948 | ie. most significant bits first). This code changes the storage to the
|
|---|
| 1949 | other way (little-endian, i.e. least significant bits first, the
|
|---|
| 1950 | way PCs store them):
|
|---|
| 1951 |
|
|---|
| 1952 | if (bit_depth == 16)
|
|---|
| 1953 | png_set_swap(png_ptr);
|
|---|
| 1954 |
|
|---|
| 1955 | If you are using packed-pixel images (1, 2, or 4 bits/pixel), and you
|
|---|
| 1956 | need to change the order the pixels are packed into bytes, you can use:
|
|---|
| 1957 |
|
|---|
| 1958 | if (bit_depth < 8)
|
|---|
| 1959 | png_set_packswap(png_ptr);
|
|---|
| 1960 |
|
|---|
| 1961 | Finally, you can write your own transformation function if none of
|
|---|
| 1962 | the existing ones meets your needs. This is done by setting a callback
|
|---|
| 1963 | with
|
|---|
| 1964 |
|
|---|
| 1965 | png_set_read_user_transform_fn(png_ptr,
|
|---|
| 1966 | read_transform_fn);
|
|---|
| 1967 |
|
|---|
| 1968 | You must supply the function
|
|---|
| 1969 |
|
|---|
| 1970 | void read_transform_fn(png_ptr ptr, row_info_ptr
|
|---|
| 1971 | row_info, png_bytep data)
|
|---|
| 1972 |
|
|---|
| 1973 | See pngtest.c for a working example. Your function will be called
|
|---|
| 1974 | after all of the other transformations have been processed.
|
|---|
| 1975 |
|
|---|
| 1976 | You can also set up a pointer to a user structure for use by your
|
|---|
| 1977 | callback function, and you can inform libpng that your transform
|
|---|
| 1978 | function will change the number of channels or bit depth with the
|
|---|
| 1979 | function
|
|---|
| 1980 |
|
|---|
| 1981 | png_set_user_transform_info(png_ptr, user_ptr,
|
|---|
| 1982 | user_depth, user_channels);
|
|---|
| 1983 |
|
|---|
| 1984 | The user's application, not libpng, is responsible for allocating and
|
|---|
| 1985 | freeing any memory required for the user structure.
|
|---|
| 1986 |
|
|---|
| 1987 | You can retrieve the pointer via the function
|
|---|
| 1988 | png_get_user_transform_ptr(). For example:
|
|---|
| 1989 |
|
|---|
| 1990 | voidp read_user_transform_ptr =
|
|---|
| 1991 | png_get_user_transform_ptr(png_ptr);
|
|---|
| 1992 |
|
|---|
| 1993 | The last thing to handle is interlacing; this is covered in detail below,
|
|---|
| 1994 | but you must call the function here if you want libpng to handle expansion
|
|---|
| 1995 | of the interlaced image.
|
|---|
| 1996 |
|
|---|
| 1997 | number_of_passes = png_set_interlace_handling(png_ptr);
|
|---|
| 1998 |
|
|---|
| 1999 | After setting the transformations, libpng can update your png_info
|
|---|
| 2000 | structure to reflect any transformations you've requested with this
|
|---|
| 2001 | call. This is most useful to update the info structure's rowbytes
|
|---|
| 2002 | field so you can use it to allocate your image memory. This function
|
|---|
| 2003 | will also update your palette with the correct screen_gamma and
|
|---|
| 2004 | background if these have been given with the calls above.
|
|---|
| 2005 |
|
|---|
| 2006 | png_read_update_info(png_ptr, info_ptr);
|
|---|
| 2007 |
|
|---|
| 2008 | After you call png_read_update_info(), you can allocate any
|
|---|
| 2009 | memory you need to hold the image. The row data is simply
|
|---|
| 2010 | raw byte data for all forms of images. As the actual allocation
|
|---|
| 2011 | varies among applications, no example will be given. If you
|
|---|
| 2012 | are allocating one large chunk, you will need to build an
|
|---|
| 2013 | array of pointers to each row, as it will be needed for some
|
|---|
| 2014 | of the functions below.
|
|---|
| 2015 |
|
|---|
| 2016 | .SS Reading image data
|
|---|
| 2017 |
|
|---|
| 2018 | After you've allocated memory, you can read the image data.
|
|---|
| 2019 | The simplest way to do this is in one function call. If you are
|
|---|
| 2020 | allocating enough memory to hold the whole image, you can just
|
|---|
| 2021 | call png_read_image() and libpng will read in all the image data
|
|---|
| 2022 | and put it in the memory area supplied. You will need to pass in
|
|---|
| 2023 | an array of pointers to each row.
|
|---|
| 2024 |
|
|---|
| 2025 | This function automatically handles interlacing, so you don't need
|
|---|
| 2026 | to call png_set_interlace_handling() or call this function multiple
|
|---|
| 2027 | times, or any of that other stuff necessary with png_read_rows().
|
|---|
| 2028 |
|
|---|
| 2029 | png_read_image(png_ptr, row_pointers);
|
|---|
| 2030 |
|
|---|
| 2031 | where row_pointers is:
|
|---|
| 2032 |
|
|---|
| 2033 | png_bytep row_pointers[height];
|
|---|
| 2034 |
|
|---|
| 2035 | You can point to void or char or whatever you use for pixels.
|
|---|
| 2036 |
|
|---|
| 2037 | If you don't want to read in the whole image at once, you can
|
|---|
| 2038 | use png_read_rows() instead. If there is no interlacing (check
|
|---|
| 2039 | interlace_type == PNG_INTERLACE_NONE), this is simple:
|
|---|
| 2040 |
|
|---|
| 2041 | png_read_rows(png_ptr, row_pointers, NULL,
|
|---|
| 2042 | number_of_rows);
|
|---|
| 2043 |
|
|---|
| 2044 | where row_pointers is the same as in the png_read_image() call.
|
|---|
| 2045 |
|
|---|
| 2046 | If you are doing this just one row at a time, you can do this with
|
|---|
| 2047 | a single row_pointer instead of an array of row_pointers:
|
|---|
| 2048 |
|
|---|
| 2049 | png_bytep row_pointer = row;
|
|---|
| 2050 | png_read_row(png_ptr, row_pointer, NULL);
|
|---|
| 2051 |
|
|---|
| 2052 | If the file is interlaced (interlace_type != 0 in the IHDR chunk), things
|
|---|
| 2053 | get somewhat harder. The only current (PNG Specification version 1.2)
|
|---|
| 2054 | interlacing type for PNG is (interlace_type == PNG_INTERLACE_ADAM7)
|
|---|
| 2055 | is a somewhat complicated 2D interlace scheme, known as Adam7, that
|
|---|
| 2056 | breaks down an image into seven smaller images of varying size, based
|
|---|
| 2057 | on an 8x8 grid.
|
|---|
| 2058 |
|
|---|
| 2059 | libpng can fill out those images or it can give them to you "as is".
|
|---|
| 2060 | If you want them filled out, there are two ways to do that. The one
|
|---|
| 2061 | mentioned in the PNG specification is to expand each pixel to cover
|
|---|
| 2062 | those pixels that have not been read yet (the "rectangle" method).
|
|---|
| 2063 | This results in a blocky image for the first pass, which gradually
|
|---|
| 2064 | smooths out as more pixels are read. The other method is the "sparkle"
|
|---|
| 2065 | method, where pixels are drawn only in their final locations, with the
|
|---|
| 2066 | rest of the image remaining whatever colors they were initialized to
|
|---|
| 2067 | before the start of the read. The first method usually looks better,
|
|---|
| 2068 | but tends to be slower, as there are more pixels to put in the rows.
|
|---|
| 2069 |
|
|---|
| 2070 | If you don't want libpng to handle the interlacing details, just call
|
|---|
| 2071 | png_read_rows() seven times to read in all seven images. Each of the
|
|---|
| 2072 | images is a valid image by itself, or they can all be combined on an
|
|---|
| 2073 | 8x8 grid to form a single image (although if you intend to combine them
|
|---|
| 2074 | you would be far better off using the libpng interlace handling).
|
|---|
| 2075 |
|
|---|
| 2076 | The first pass will return an image 1/8 as wide as the entire image
|
|---|
| 2077 | (every 8th column starting in column 0) and 1/8 as high as the original
|
|---|
| 2078 | (every 8th row starting in row 0), the second will be 1/8 as wide
|
|---|
| 2079 | (starting in column 4) and 1/8 as high (also starting in row 0). The
|
|---|
| 2080 | third pass will be 1/4 as wide (every 4th pixel starting in column 0) and
|
|---|
| 2081 | 1/8 as high (every 8th row starting in row 4), and the fourth pass will
|
|---|
| 2082 | be 1/4 as wide and 1/4 as high (every 4th column starting in column 2,
|
|---|
| 2083 | and every 4th row starting in row 0). The fifth pass will return an
|
|---|
| 2084 | image 1/2 as wide, and 1/4 as high (starting at column 0 and row 2),
|
|---|
| 2085 | while the sixth pass will be 1/2 as wide and 1/2 as high as the original
|
|---|
| 2086 | (starting in column 1 and row 0). The seventh and final pass will be as
|
|---|
| 2087 | wide as the original, and 1/2 as high, containing all of the odd
|
|---|
| 2088 | numbered scanlines. Phew!
|
|---|
| 2089 |
|
|---|
| 2090 | If you want libpng to expand the images, call this before calling
|
|---|
| 2091 | png_start_read_image() or png_read_update_info():
|
|---|
| 2092 |
|
|---|
| 2093 | if (interlace_type == PNG_INTERLACE_ADAM7)
|
|---|
| 2094 | number_of_passes
|
|---|
| 2095 | = png_set_interlace_handling(png_ptr);
|
|---|
| 2096 |
|
|---|
| 2097 | This will return the number of passes needed. Currently, this
|
|---|
| 2098 | is seven, but may change if another interlace type is added.
|
|---|
| 2099 | This function can be called even if the file is not interlaced,
|
|---|
| 2100 | where it will return one pass.
|
|---|
| 2101 |
|
|---|
| 2102 | If you are not going to display the image after each pass, but are
|
|---|
| 2103 | going to wait until the entire image is read in, use the sparkle
|
|---|
| 2104 | effect. This effect is faster and the end result of either method
|
|---|
| 2105 | is exactly the same. If you are planning on displaying the image
|
|---|
| 2106 | after each pass, the "rectangle" effect is generally considered the
|
|---|
| 2107 | better looking one.
|
|---|
| 2108 |
|
|---|
| 2109 | If you only want the "sparkle" effect, just call png_read_rows() as
|
|---|
| 2110 | normal, with the third parameter NULL. Make sure you make pass over
|
|---|
| 2111 | the image number_of_passes times, and you don't change the data in the
|
|---|
| 2112 | rows between calls. You can change the locations of the data, just
|
|---|
| 2113 | not the data. Each pass only writes the pixels appropriate for that
|
|---|
| 2114 | pass, and assumes the data from previous passes is still valid.
|
|---|
| 2115 |
|
|---|
| 2116 | png_read_rows(png_ptr, row_pointers, NULL,
|
|---|
| 2117 | number_of_rows);
|
|---|
| 2118 |
|
|---|
| 2119 | If you only want the first effect (the rectangles), do the same as
|
|---|
| 2120 | before except pass the row buffer in the third parameter, and leave
|
|---|
| 2121 | the second parameter NULL.
|
|---|
| 2122 |
|
|---|
| 2123 | png_read_rows(png_ptr, NULL, row_pointers,
|
|---|
| 2124 | number_of_rows);
|
|---|
| 2125 |
|
|---|
| 2126 | .SS Finishing a sequential read
|
|---|
| 2127 |
|
|---|
| 2128 | After you are finished reading the image through the
|
|---|
| 2129 | low-level interface, you can finish reading the file. If you are
|
|---|
| 2130 | interested in comments or time, which may be stored either before or
|
|---|
| 2131 | after the image data, you should pass the separate png_info struct if
|
|---|
| 2132 | you want to keep the comments from before and after the image
|
|---|
| 2133 | separate. If you are not interested, you can pass NULL.
|
|---|
| 2134 |
|
|---|
| 2135 | png_read_end(png_ptr, end_info);
|
|---|
| 2136 |
|
|---|
| 2137 | When you are done, you can free all memory allocated by libpng like this:
|
|---|
| 2138 |
|
|---|
| 2139 | png_destroy_read_struct(&png_ptr, &info_ptr,
|
|---|
| 2140 | &end_info);
|
|---|
| 2141 |
|
|---|
| 2142 | It is also possible to individually free the info_ptr members that
|
|---|
| 2143 | point to libpng-allocated storage with the following function:
|
|---|
| 2144 |
|
|---|
| 2145 | png_free_data(png_ptr, info_ptr, mask, seq)
|
|---|
| 2146 | mask - identifies data to be freed, a mask
|
|---|
| 2147 | containing the bitwise OR of one or
|
|---|
| 2148 | more of
|
|---|
| 2149 | PNG_FREE_PLTE, PNG_FREE_TRNS,
|
|---|
| 2150 | PNG_FREE_HIST, PNG_FREE_ICCP,
|
|---|
| 2151 | PNG_FREE_PCAL, PNG_FREE_ROWS,
|
|---|
| 2152 | PNG_FREE_SCAL, PNG_FREE_SPLT,
|
|---|
| 2153 | PNG_FREE_TEXT, PNG_FREE_UNKN,
|
|---|
| 2154 | or simply PNG_FREE_ALL
|
|---|
| 2155 | seq - sequence number of item to be freed
|
|---|
| 2156 | (-1 for all items)
|
|---|
| 2157 |
|
|---|
| 2158 | This function may be safely called when the relevant storage has
|
|---|
| 2159 | already been freed, or has not yet been allocated, or was allocated
|
|---|
| 2160 | by the user and not by libpng, and will in those
|
|---|
| 2161 | cases do nothing. The "seq" parameter is ignored if only one item
|
|---|
| 2162 | of the selected data type, such as PLTE, is allowed. If "seq" is not
|
|---|
| 2163 | -1, and multiple items are allowed for the data type identified in
|
|---|
| 2164 | the mask, such as text or sPLT, only the n'th item in the structure
|
|---|
| 2165 | is freed, where n is "seq".
|
|---|
| 2166 |
|
|---|
| 2167 | The default behavior is only to free data that was allocated internally
|
|---|
| 2168 | by libpng. This can be changed, so that libpng will not free the data,
|
|---|
| 2169 | or so that it will free data that was allocated by the user with png_malloc()
|
|---|
| 2170 | or png_zalloc() and passed in via a png_set_*() function, with
|
|---|
| 2171 |
|
|---|
| 2172 | png_data_freer(png_ptr, info_ptr, freer, mask)
|
|---|
| 2173 | mask - which data elements are affected
|
|---|
| 2174 | same choices as in png_free_data()
|
|---|
| 2175 | freer - one of
|
|---|
| 2176 | PNG_DESTROY_WILL_FREE_DATA
|
|---|
| 2177 | PNG_SET_WILL_FREE_DATA
|
|---|
| 2178 | PNG_USER_WILL_FREE_DATA
|
|---|
| 2179 |
|
|---|
| 2180 | This function only affects data that has already been allocated.
|
|---|
| 2181 | You can call this function after reading the PNG data but before calling
|
|---|
| 2182 | any png_set_*() functions, to control whether the user or the png_set_*()
|
|---|
| 2183 | function is responsible for freeing any existing data that might be present,
|
|---|
| 2184 | and again after the png_set_*() functions to control whether the user
|
|---|
| 2185 | or png_destroy_*() is supposed to free the data. When the user assumes
|
|---|
| 2186 | responsibility for libpng-allocated data, the application must use
|
|---|
| 2187 | png_free() to free it, and when the user transfers responsibility to libpng
|
|---|
| 2188 | for data that the user has allocated, the user must have used png_malloc()
|
|---|
| 2189 | or png_zalloc() to allocate it.
|
|---|
| 2190 |
|
|---|
| 2191 | If you allocated your row_pointers in a single block, as suggested above in
|
|---|
| 2192 | the description of the high level read interface, you must not transfer
|
|---|
| 2193 | responsibility for freeing it to the png_set_rows or png_read_destroy function,
|
|---|
| 2194 | because they would also try to free the individual row_pointers[i].
|
|---|
| 2195 |
|
|---|
| 2196 | If you allocated text_ptr.text, text_ptr.lang, and text_ptr.translated_keyword
|
|---|
| 2197 | separately, do not transfer responsibility for freeing text_ptr to libpng,
|
|---|
| 2198 | because when libpng fills a png_text structure it combines these members with
|
|---|
| 2199 | the key member, and png_free_data() will free only text_ptr.key. Similarly,
|
|---|
| 2200 | if you transfer responsibility for free'ing text_ptr from libpng to your
|
|---|
| 2201 | application, your application must not separately free those members.
|
|---|
| 2202 |
|
|---|
| 2203 | The png_free_data() function will turn off the "valid" flag for anything
|
|---|
| 2204 | it frees. If you need to turn the flag off for a chunk that was freed by your
|
|---|
| 2205 | application instead of by libpng, you can use
|
|---|
| 2206 |
|
|---|
| 2207 | png_set_invalid(png_ptr, info_ptr, mask);
|
|---|
| 2208 | mask - identifies the chunks to be made invalid,
|
|---|
| 2209 | containing the bitwise OR of one or
|
|---|
| 2210 | more of
|
|---|
| 2211 | PNG_INFO_gAMA, PNG_INFO_sBIT,
|
|---|
| 2212 | PNG_INFO_cHRM, PNG_INFO_PLTE,
|
|---|
| 2213 | PNG_INFO_tRNS, PNG_INFO_bKGD,
|
|---|
| 2214 | PNG_INFO_hIST, PNG_INFO_pHYs,
|
|---|
| 2215 | PNG_INFO_oFFs, PNG_INFO_tIME,
|
|---|
| 2216 | PNG_INFO_pCAL, PNG_INFO_sRGB,
|
|---|
| 2217 | PNG_INFO_iCCP, PNG_INFO_sPLT,
|
|---|
| 2218 | PNG_INFO_sCAL, PNG_INFO_IDAT
|
|---|
| 2219 |
|
|---|
| 2220 | For a more compact example of reading a PNG image, see the file example.c.
|
|---|
| 2221 |
|
|---|
| 2222 | .SS Reading PNG files progressively
|
|---|
| 2223 |
|
|---|
| 2224 | The progressive reader is slightly different then the non-progressive
|
|---|
| 2225 | reader. Instead of calling png_read_info(), png_read_rows(), and
|
|---|
| 2226 | png_read_end(), you make one call to png_process_data(), which calls
|
|---|
| 2227 | callbacks when it has the info, a row, or the end of the image. You
|
|---|
| 2228 | set up these callbacks with png_set_progressive_read_fn(). You don't
|
|---|
| 2229 | have to worry about the input/output functions of libpng, as you are
|
|---|
| 2230 | giving the library the data directly in png_process_data(). I will
|
|---|
| 2231 | assume that you have read the section on reading PNG files above,
|
|---|
| 2232 | so I will only highlight the differences (although I will show
|
|---|
| 2233 | all of the code).
|
|---|
| 2234 |
|
|---|
| 2235 | png_structp png_ptr;
|
|---|
| 2236 | png_infop info_ptr;
|
|---|
| 2237 |
|
|---|
| 2238 | /* An example code fragment of how you would
|
|---|
| 2239 | initialize the progressive reader in your
|
|---|
| 2240 | application. */
|
|---|
| 2241 | int
|
|---|
| 2242 | initialize_png_reader()
|
|---|
| 2243 | {
|
|---|
| 2244 | png_ptr = png_create_read_struct
|
|---|
| 2245 | (PNG_LIBPNG_VER_STRING, (png_voidp)user_error_ptr,
|
|---|
| 2246 | user_error_fn, user_warning_fn);
|
|---|
| 2247 | if (!png_ptr)
|
|---|
| 2248 | return (ERROR);
|
|---|
| 2249 | info_ptr = png_create_info_struct(png_ptr);
|
|---|
| 2250 | if (!info_ptr)
|
|---|
| 2251 | {
|
|---|
| 2252 | png_destroy_read_struct(&png_ptr, (png_infopp)NULL,
|
|---|
| 2253 | (png_infopp)NULL);
|
|---|
| 2254 | return (ERROR);
|
|---|
| 2255 | }
|
|---|
| 2256 |
|
|---|
| 2257 | if (setjmp(png_jmpbuf(png_ptr)))
|
|---|
| 2258 | {
|
|---|
| 2259 | png_destroy_read_struct(&png_ptr, &info_ptr,
|
|---|
| 2260 | (png_infopp)NULL);
|
|---|
| 2261 | return (ERROR);
|
|---|
| 2262 | }
|
|---|
| 2263 |
|
|---|
| 2264 | /* This one's new. You can provide functions
|
|---|
| 2265 | to be called when the header info is valid,
|
|---|
| 2266 | when each row is completed, and when the image
|
|---|
| 2267 | is finished. If you aren't using all functions,
|
|---|
| 2268 | you can specify NULL parameters. Even when all
|
|---|
| 2269 | three functions are NULL, you need to call
|
|---|
| 2270 | png_set_progressive_read_fn(). You can use
|
|---|
| 2271 | any struct as the user_ptr (cast to a void pointer
|
|---|
| 2272 | for the function call), and retrieve the pointer
|
|---|
| 2273 | from inside the callbacks using the function
|
|---|
| 2274 |
|
|---|
| 2275 | png_get_progressive_ptr(png_ptr);
|
|---|
| 2276 |
|
|---|
| 2277 | which will return a void pointer, which you have
|
|---|
| 2278 | to cast appropriately.
|
|---|
| 2279 | */
|
|---|
| 2280 | png_set_progressive_read_fn(png_ptr, (void *)user_ptr,
|
|---|
| 2281 | info_callback, row_callback, end_callback);
|
|---|
| 2282 |
|
|---|
| 2283 | return 0;
|
|---|
| 2284 | }
|
|---|
| 2285 |
|
|---|
| 2286 | /* A code fragment that you call as you receive blocks
|
|---|
| 2287 | of data */
|
|---|
| 2288 | int
|
|---|
| 2289 | process_data(png_bytep buffer, png_uint_32 length)
|
|---|
| 2290 | {
|
|---|
| 2291 | if (setjmp(png_jmpbuf(png_ptr)))
|
|---|
| 2292 | {
|
|---|
| 2293 | png_destroy_read_struct(&png_ptr, &info_ptr,
|
|---|
| 2294 | (png_infopp)NULL);
|
|---|
| 2295 | return (ERROR);
|
|---|
| 2296 | }
|
|---|
| 2297 |
|
|---|
| 2298 | /* This one's new also. Simply give it a chunk
|
|---|
| 2299 | of data from the file stream (in order, of
|
|---|
| 2300 | course). On machines with segmented memory
|
|---|
| 2301 | models machines, don't give it any more than
|
|---|
| 2302 | 64K. The library seems to run fine with sizes
|
|---|
| 2303 | of 4K. Although you can give it much less if
|
|---|
| 2304 | necessary (I assume you can give it chunks of
|
|---|
| 2305 | 1 byte, I haven't tried less then 256 bytes
|
|---|
| 2306 | yet). When this function returns, you may
|
|---|
| 2307 | want to display any rows that were generated
|
|---|
| 2308 | in the row callback if you don't already do
|
|---|
| 2309 | so there.
|
|---|
| 2310 | */
|
|---|
| 2311 | png_process_data(png_ptr, info_ptr, buffer, length);
|
|---|
| 2312 | return 0;
|
|---|
| 2313 | }
|
|---|
| 2314 |
|
|---|
| 2315 | /* This function is called (as set by
|
|---|
| 2316 | png_set_progressive_read_fn() above) when enough data
|
|---|
| 2317 | has been supplied so all of the header has been
|
|---|
| 2318 | read.
|
|---|
| 2319 | */
|
|---|
| 2320 | void
|
|---|
| 2321 | info_callback(png_structp png_ptr, png_infop info)
|
|---|
| 2322 | {
|
|---|
| 2323 | /* Do any setup here, including setting any of
|
|---|
| 2324 | the transformations mentioned in the Reading
|
|---|
| 2325 | PNG files section. For now, you _must_ call
|
|---|
| 2326 | either png_start_read_image() or
|
|---|
| 2327 | png_read_update_info() after all the
|
|---|
| 2328 | transformations are set (even if you don't set
|
|---|
| 2329 | any). You may start getting rows before
|
|---|
| 2330 | png_process_data() returns, so this is your
|
|---|
| 2331 | last chance to prepare for that.
|
|---|
| 2332 | */
|
|---|
| 2333 | }
|
|---|
| 2334 |
|
|---|
| 2335 | /* This function is called when each row of image
|
|---|
| 2336 | data is complete */
|
|---|
| 2337 | void
|
|---|
| 2338 | row_callback(png_structp png_ptr, png_bytep new_row,
|
|---|
| 2339 | png_uint_32 row_num, int pass)
|
|---|
| 2340 | {
|
|---|
| 2341 | /* If the image is interlaced, and you turned
|
|---|
| 2342 | on the interlace handler, this function will
|
|---|
| 2343 | be called for every row in every pass. Some
|
|---|
| 2344 | of these rows will not be changed from the
|
|---|
| 2345 | previous pass. When the row is not changed,
|
|---|
| 2346 | the new_row variable will be NULL. The rows
|
|---|
| 2347 | and passes are called in order, so you don't
|
|---|
| 2348 | really need the row_num and pass, but I'm
|
|---|
| 2349 | supplying them because it may make your life
|
|---|
| 2350 | easier.
|
|---|
| 2351 |
|
|---|
| 2352 | For the non-NULL rows of interlaced images,
|
|---|
| 2353 | you must call png_progressive_combine_row()
|
|---|
| 2354 | passing in the row and the old row. You can
|
|---|
| 2355 | call this function for NULL rows (it will just
|
|---|
| 2356 | return) and for non-interlaced images (it just
|
|---|
| 2357 | does the memcpy for you) if it will make the
|
|---|
| 2358 | code easier. Thus, you can just do this for
|
|---|
| 2359 | all cases:
|
|---|
| 2360 | */
|
|---|
| 2361 |
|
|---|
| 2362 | png_progressive_combine_row(png_ptr, old_row,
|
|---|
| 2363 | new_row);
|
|---|
| 2364 |
|
|---|
| 2365 | /* where old_row is what was displayed for
|
|---|
| 2366 | previously for the row. Note that the first
|
|---|
| 2367 | pass (pass == 0, really) will completely cover
|
|---|
| 2368 | the old row, so the rows do not have to be
|
|---|
| 2369 | initialized. After the first pass (and only
|
|---|
| 2370 | for interlaced images), you will have to pass
|
|---|
| 2371 | the current row, and the function will combine
|
|---|
| 2372 | the old row and the new row.
|
|---|
| 2373 | */
|
|---|
| 2374 | }
|
|---|
| 2375 |
|
|---|
| 2376 | void
|
|---|
| 2377 | end_callback(png_structp png_ptr, png_infop info)
|
|---|
| 2378 | {
|
|---|
| 2379 | /* This function is called after the whole image
|
|---|
| 2380 | has been read, including any chunks after the
|
|---|
| 2381 | image (up to and including the IEND). You
|
|---|
| 2382 | will usually have the same info chunk as you
|
|---|
| 2383 | had in the header, although some data may have
|
|---|
| 2384 | been added to the comments and time fields.
|
|---|
| 2385 |
|
|---|
| 2386 | Most people won't do much here, perhaps setting
|
|---|
| 2387 | a flag that marks the image as finished.
|
|---|
| 2388 | */
|
|---|
| 2389 | }
|
|---|
| 2390 |
|
|---|
| 2391 |
|
|---|
| 2392 |
|
|---|
| 2393 | .SH IV. Writing
|
|---|
| 2394 |
|
|---|
| 2395 | Much of this is very similar to reading. However, everything of
|
|---|
| 2396 | importance is repeated here, so you won't have to constantly look
|
|---|
| 2397 | back up in the reading section to understand writing.
|
|---|
| 2398 |
|
|---|
| 2399 | .SS Setup
|
|---|
| 2400 |
|
|---|
| 2401 | You will want to do the I/O initialization before you get into libpng,
|
|---|
| 2402 | so if it doesn't work, you don't have anything to undo. If you are not
|
|---|
| 2403 | using the standard I/O functions, you will need to replace them with
|
|---|
| 2404 | custom writing functions. See the discussion under Customizing libpng.
|
|---|
| 2405 |
|
|---|
| 2406 | FILE *fp = fopen(file_name, "wb");
|
|---|
| 2407 | if (!fp)
|
|---|
| 2408 | {
|
|---|
| 2409 | return (ERROR);
|
|---|
| 2410 | }
|
|---|
| 2411 |
|
|---|
| 2412 | Next, png_struct and png_info need to be allocated and initialized.
|
|---|
| 2413 | As these can be both relatively large, you may not want to store these
|
|---|
| 2414 | on the stack, unless you have stack space to spare. Of course, you
|
|---|
| 2415 | will want to check if they return NULL. If you are also reading,
|
|---|
| 2416 | you won't want to name your read structure and your write structure
|
|---|
| 2417 | both "png_ptr"; you can call them anything you like, such as
|
|---|
| 2418 | "read_ptr" and "write_ptr". Look at pngtest.c, for example.
|
|---|
| 2419 |
|
|---|
| 2420 | png_structp png_ptr = png_create_write_struct
|
|---|
| 2421 | (PNG_LIBPNG_VER_STRING, (png_voidp)user_error_ptr,
|
|---|
| 2422 | user_error_fn, user_warning_fn);
|
|---|
| 2423 | if (!png_ptr)
|
|---|
| 2424 | return (ERROR);
|
|---|
| 2425 |
|
|---|
| 2426 | png_infop info_ptr = png_create_info_struct(png_ptr);
|
|---|
| 2427 | if (!info_ptr)
|
|---|
| 2428 | {
|
|---|
| 2429 | png_destroy_write_struct(&png_ptr,
|
|---|
| 2430 | (png_infopp)NULL);
|
|---|
| 2431 | return (ERROR);
|
|---|
| 2432 | }
|
|---|
| 2433 |
|
|---|
| 2434 | If you want to use your own memory allocation routines,
|
|---|
| 2435 | define PNG_USER_MEM_SUPPORTED and use
|
|---|
| 2436 | png_create_write_struct_2() instead of png_create_write_struct():
|
|---|
| 2437 |
|
|---|
| 2438 | png_structp png_ptr = png_create_write_struct_2
|
|---|
| 2439 | (PNG_LIBPNG_VER_STRING, (png_voidp)user_error_ptr,
|
|---|
| 2440 | user_error_fn, user_warning_fn, (png_voidp)
|
|---|
| 2441 | user_mem_ptr, user_malloc_fn, user_free_fn);
|
|---|
| 2442 |
|
|---|
| 2443 | After you have these structures, you will need to set up the
|
|---|
| 2444 | error handling. When libpng encounters an error, it expects to
|
|---|
| 2445 | longjmp() back to your routine. Therefore, you will need to call
|
|---|
| 2446 | setjmp() and pass the png_jmpbuf(png_ptr). If you
|
|---|
| 2447 | write the file from different routines, you will need to update
|
|---|
| 2448 | the png_jmpbuf(png_ptr) every time you enter a new routine that will
|
|---|
| 2449 | call a png_*() function. See your documentation of setjmp/longjmp
|
|---|
| 2450 | for your compiler for more information on setjmp/longjmp. See
|
|---|
| 2451 | the discussion on libpng error handling in the Customizing Libpng
|
|---|
| 2452 | section below for more information on the libpng error handling.
|
|---|
| 2453 |
|
|---|
| 2454 | if (setjmp(png_jmpbuf(png_ptr)))
|
|---|
| 2455 | {
|
|---|
| 2456 | png_destroy_write_struct(&png_ptr, &info_ptr);
|
|---|
| 2457 | fclose(fp);
|
|---|
| 2458 | return (ERROR);
|
|---|
| 2459 | }
|
|---|
| 2460 | ...
|
|---|
| 2461 | return;
|
|---|
| 2462 |
|
|---|
| 2463 | If you would rather avoid the complexity of setjmp/longjmp issues,
|
|---|
| 2464 | you can compile libpng with PNG_SETJMP_NOT_SUPPORTED, in which case
|
|---|
| 2465 | errors will result in a call to PNG_ABORT() which defaults to abort().
|
|---|
| 2466 |
|
|---|
| 2467 | Now you need to set up the output code. The default for libpng is to
|
|---|
| 2468 | use the C function fwrite(). If you use this, you will need to pass a
|
|---|
| 2469 | valid FILE * in the function png_init_io(). Be sure that the file is
|
|---|
| 2470 | opened in binary mode. Again, if you wish to handle writing data in
|
|---|
| 2471 | another way, see the discussion on libpng I/O handling in the Customizing
|
|---|
| 2472 | Libpng section below.
|
|---|
| 2473 |
|
|---|
| 2474 | png_init_io(png_ptr, fp);
|
|---|
| 2475 |
|
|---|
| 2476 | If you are embedding your PNG into a datastream such as MNG, and don't
|
|---|
| 2477 | want libpng to write the 8-byte signature, or if you have already
|
|---|
| 2478 | written the signature in your application, use
|
|---|
| 2479 |
|
|---|
| 2480 | png_set_sig_bytes(png_ptr, 8);
|
|---|
| 2481 |
|
|---|
| 2482 | to inform libpng that it should not write a signature.
|
|---|
| 2483 |
|
|---|
| 2484 | .SS Write callbacks
|
|---|
| 2485 |
|
|---|
| 2486 | At this point, you can set up a callback function that will be
|
|---|
| 2487 | called after each row has been written, which you can use to control
|
|---|
| 2488 | a progress meter or the like. It's demonstrated in pngtest.c.
|
|---|
| 2489 | You must supply a function
|
|---|
| 2490 |
|
|---|
| 2491 | void write_row_callback(png_ptr, png_uint_32 row,
|
|---|
| 2492 | int pass);
|
|---|
| 2493 | {
|
|---|
| 2494 | /* put your code here */
|
|---|
| 2495 | }
|
|---|
| 2496 |
|
|---|
| 2497 | (You can give it another name that you like instead of "write_row_callback")
|
|---|
| 2498 |
|
|---|
| 2499 | To inform libpng about your function, use
|
|---|
| 2500 |
|
|---|
| 2501 | png_set_write_status_fn(png_ptr, write_row_callback);
|
|---|
| 2502 |
|
|---|
| 2503 | You now have the option of modifying how the compression library will
|
|---|
| 2504 | run. The following functions are mainly for testing, but may be useful
|
|---|
| 2505 | in some cases, like if you need to write PNG files extremely fast and
|
|---|
| 2506 | are willing to give up some compression, or if you want to get the
|
|---|
| 2507 | maximum possible compression at the expense of slower writing. If you
|
|---|
| 2508 | have no special needs in this area, let the library do what it wants by
|
|---|
| 2509 | not calling this function at all, as it has been tuned to deliver a good
|
|---|
| 2510 | speed/compression ratio. The second parameter to png_set_filter() is
|
|---|
| 2511 | the filter method, for which the only valid values are 0 (as of the
|
|---|
| 2512 | July 1999 PNG specification, version 1.2) or 64 (if you are writing
|
|---|
| 2513 | a PNG datastream that is to be embedded in a MNG datastream). The third
|
|---|
| 2514 | parameter is a flag that indicates which filter type(s) are to be tested
|
|---|
| 2515 | for each scanline. See the PNG specification for details on the specific filter
|
|---|
| 2516 | types.
|
|---|
| 2517 |
|
|---|
| 2518 |
|
|---|
| 2519 | /* turn on or off filtering, and/or choose
|
|---|
| 2520 | specific filters. You can use either a single
|
|---|
| 2521 | PNG_FILTER_VALUE_NAME or the bitwise OR of one
|
|---|
| 2522 | or more PNG_FILTER_NAME masks. */
|
|---|
| 2523 | png_set_filter(png_ptr, 0,
|
|---|
| 2524 | PNG_FILTER_NONE | PNG_FILTER_VALUE_NONE |
|
|---|
| 2525 | PNG_FILTER_SUB | PNG_FILTER_VALUE_SUB |
|
|---|
| 2526 | PNG_FILTER_UP | PNG_FILTER_VALUE_UP |
|
|---|
| 2527 | PNG_FILTER_AVG | PNG_FILTER_VALUE_AVG |
|
|---|
| 2528 | PNG_FILTER_PAETH | PNG_FILTER_VALUE_PAETH|
|
|---|
| 2529 | PNG_ALL_FILTERS);
|
|---|
| 2530 |
|
|---|
| 2531 | If an application
|
|---|
| 2532 | wants to start and stop using particular filters during compression,
|
|---|
| 2533 | it should start out with all of the filters (to ensure that the previous
|
|---|
| 2534 | row of pixels will be stored in case it's needed later), and then add
|
|---|
| 2535 | and remove them after the start of compression.
|
|---|
| 2536 |
|
|---|
| 2537 | If you are writing a PNG datastream that is to be embedded in a MNG
|
|---|
| 2538 | datastream, the second parameter can be either 0 or 64.
|
|---|
| 2539 |
|
|---|
| 2540 | The png_set_compression_*() functions interface to the zlib compression
|
|---|
| 2541 | library, and should mostly be ignored unless you really know what you are
|
|---|
| 2542 | doing. The only generally useful call is png_set_compression_level()
|
|---|
| 2543 | which changes how much time zlib spends on trying to compress the image
|
|---|
| 2544 | data. See the Compression Library (zlib.h and algorithm.txt, distributed
|
|---|
| 2545 | with zlib) for details on the compression levels.
|
|---|
| 2546 |
|
|---|
| 2547 | /* set the zlib compression level */
|
|---|
| 2548 | png_set_compression_level(png_ptr,
|
|---|
| 2549 | Z_BEST_COMPRESSION);
|
|---|
| 2550 |
|
|---|
| 2551 | /* set other zlib parameters */
|
|---|
| 2552 | png_set_compression_mem_level(png_ptr, 8);
|
|---|
| 2553 | png_set_compression_strategy(png_ptr,
|
|---|
| 2554 | Z_DEFAULT_STRATEGY);
|
|---|
| 2555 | png_set_compression_window_bits(png_ptr, 15);
|
|---|
| 2556 | png_set_compression_method(png_ptr, 8);
|
|---|
| 2557 | png_set_compression_buffer_size(png_ptr, 8192)
|
|---|
| 2558 |
|
|---|
| 2559 | extern PNG_EXPORT(void,png_set_zbuf_size)
|
|---|
| 2560 |
|
|---|
| 2561 | .SS Setting the contents of info for output
|
|---|
| 2562 |
|
|---|
| 2563 | You now need to fill in the png_info structure with all the data you
|
|---|
| 2564 | wish to write before the actual image. Note that the only thing you
|
|---|
| 2565 | are allowed to write after the image is the text chunks and the time
|
|---|
| 2566 | chunk (as of PNG Specification 1.2, anyway). See png_write_end() and
|
|---|
| 2567 | the latest PNG specification for more information on that. If you
|
|---|
| 2568 | wish to write them before the image, fill them in now, and flag that
|
|---|
| 2569 | data as being valid. If you want to wait until after the data, don't
|
|---|
| 2570 | fill them until png_write_end(). For all the fields in png_info and
|
|---|
| 2571 | their data types, see png.h. For explanations of what the fields
|
|---|
| 2572 | contain, see the PNG specification.
|
|---|
| 2573 |
|
|---|
| 2574 | Some of the more important parts of the png_info are:
|
|---|
| 2575 |
|
|---|
| 2576 | png_set_IHDR(png_ptr, info_ptr, width, height,
|
|---|
| 2577 | bit_depth, color_type, interlace_type,
|
|---|
| 2578 | compression_type, filter_method)
|
|---|
| 2579 | width - holds the width of the image
|
|---|
| 2580 | in pixels (up to 2^31).
|
|---|
| 2581 | height - holds the height of the image
|
|---|
| 2582 | in pixels (up to 2^31).
|
|---|
| 2583 | bit_depth - holds the bit depth of one of the
|
|---|
| 2584 | image channels.
|
|---|
| 2585 | (valid values are 1, 2, 4, 8, 16
|
|---|
| 2586 | and depend also on the
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