source: trunk/src/3rdparty/libjpeg/jcparam.c@ 764

/*
 * jcparam.c
 *
 * Copyright (C) 1991-1998, Thomas G. Lane.
 * This file is part of the Independent JPEG Group's software.
 * For conditions of distribution and use, see the accompanying README file.
 *
 * This file contains optional default-setting code for the JPEG compressor.
 * Applications do not have to use this file, but those that don't use it
 * must know a lot more about the innards of the JPEG code.
 */

#define JPEG_INTERNALS
#include "jinclude.h"
#include "jpeglib.h"


/*
 * Quantization table setup routines
 */

GLOBAL(void)
jpeg_add_quant_table (j_compress_ptr cinfo, int which_tbl,
                      const unsigned int *basic_table,
                      int scale_factor, boolean force_baseline)
/* Define a quantization table equal to the basic_table times
 * a scale factor (given as a percentage).
 * If force_baseline is TRUE, the computed quantization table entries
 * are limited to 1..255 for JPEG baseline compatibility.
 */
{
  JQUANT_TBL ** qtblptr;
  int i;
  long temp;

  /* Safety check to ensure start_compress not called yet. */
  if (cinfo->global_state != CSTATE_START)
    ERREXIT1(cinfo, JERR_BAD_STATE, cinfo->global_state);

  if (which_tbl < 0 || which_tbl >= NUM_QUANT_TBLS)
    ERREXIT1(cinfo, JERR_DQT_INDEX, which_tbl);

  qtblptr = & cinfo->quant_tbl_ptrs[which_tbl];

  if (*qtblptr == NULL)
    *qtblptr = jpeg_alloc_quant_table((j_common_ptr) cinfo);

  for (i = 0; i < DCTSIZE2; i++) {
    temp = ((long) basic_table[i] * scale_factor + 50L) / 100L;
    /* limit the values to the valid range */
    if (temp <= 0L) temp = 1L;
    if (temp > 32767L) temp = 32767L; /* max quantizer needed for 12 bits */
    if (force_baseline && temp > 255L)
      temp = 255L;              /* limit to baseline range if requested */
    (*qtblptr)->quantval[i] = (UINT16) temp;
  }

  /* Initialize sent_table FALSE so table will be written to JPEG file. */
  (*qtblptr)->sent_table = FALSE;
}


GLOBAL(void)
jpeg_set_linear_quality (j_compress_ptr cinfo, int scale_factor,
                         boolean force_baseline)
/* Set or change the 'quality' (quantization) setting, using default tables
 * and a straight percentage-scaling quality scale.  In most cases it's better
 * to use jpeg_set_quality (below); this entry point is provided for
 * applications that insist on a linear percentage scaling.
 */
{
  /* These are the sample quantization tables given in JPEG spec section K.1.
   * The spec says that the values given produce "good" quality, and
   * when divided by 2, "very good" quality.
   */
  static const unsigned int std_luminance_quant_tbl[DCTSIZE2] = {
    16,  11,  10,  16,  24,  40,  51,  61,
    12,  12,  14,  19,  26,  58,  60,  55,
    14,  13,  16,  24,  40,  57,  69,  56,
    14,  17,  22,  29,  51,  87,  80,  62,
    18,  22,  37,  56,  68, 109, 103,  77,
    24,  35,  55,  64,  81, 104, 113,  92,
    49,  64,  78,  87, 103, 121, 120, 101,
    72,  92,  95,  98, 112, 100, 103,  99
  };
  static const unsigned int std_chrominance_quant_tbl[DCTSIZE2] = {
    17,  18,  24,  47,  99,  99,  99,  99,
    18,  21,  26,  66,  99,  99,  99,  99,
    24,  26,  56,  99,  99,  99,  99,  99,
    47,  66,  99,  99,  99,  99,  99,  99,
    99,  99,  99,  99,  99,  99,  99,  99,
    99,  99,  99,  99,  99,  99,  99,  99,
    99,  99,  99,  99,  99,  99,  99,  99,
    99,  99,  99,  99,  99,  99,  99,  99
  };

  /* Set up two quantization tables using the specified scaling */
  jpeg_add_quant_table(cinfo, 0, std_luminance_quant_tbl,
                       scale_factor, force_baseline);
  jpeg_add_quant_table(cinfo, 1, std_chrominance_quant_tbl,
                       scale_factor, force_baseline);
}


GLOBAL(int)
jpeg_quality_scaling (int quality)
/* Convert a user-specified quality rating to a percentage scaling factor
 * for an underlying quantization table, using our recommended scaling curve.
 * The input 'quality' factor should be 0 (terrible) to 100 (very good).
 */
{
  /* Safety limit on quality factor.  Convert 0 to 1 to avoid zero divide. */
  if (quality <= 0) quality = 1;
  if (quality > 100) quality = 100;

  /* The basic table is used as-is (scaling 100) for a quality of 50.
   * Qualities 50..100 are converted to scaling percentage 200 - 2*Q;
   * note that at Q=100 the scaling is 0, which will cause jpeg_add_quant_table
   * to make all the table entries 1 (hence, minimum quantization loss).
   * Qualities 1..50 are converted to scaling percentage 5000/Q.
   */
  if (quality < 50)
    quality = 5000 / quality;
  else
    quality = 200 - quality*2;

  return quality;
}


GLOBAL(void)
jpeg_set_quality (j_compress_ptr cinfo, int quality, boolean force_baseline)
/* Set or change the 'quality' (quantization) setting, using default tables.
 * This is the standard quality-adjusting entry point for typical user
 * interfaces; only those who want detailed control over quantization tables
 * would use the preceding three routines directly.
 */
{
  /* Convert user 0-100 rating to percentage scaling */
  quality = jpeg_quality_scaling(quality);

  /* Set up standard quality tables */
  jpeg_set_linear_quality(cinfo, quality, force_baseline);
}


/*
 * Huffman table setup routines
 */

LOCAL(void)
add_huff_table (j_compress_ptr cinfo,
                JHUFF_TBL **htblptr, const UINT8 *bits, const UINT8 *val)
/* Define a Huffman table */
{
  int nsymbols, len;

  if (*htblptr == NULL)
    *htblptr = jpeg_alloc_huff_table((j_common_ptr) cinfo);

  /* Copy the number-of-symbols-of-each-code-length counts */
  MEMCOPY((*htblptr)->bits, bits, SIZEOF((*htblptr)->bits));

  /* Validate the counts.  We do this here mainly so we can copy the right
   * number of symbols from the val[] array, without risking marching off
   * the end of memory.  jchuff.c will do a more thorough test later.
   */
  nsymbols = 0;
  for (len = 1; len <= 16; len++)
    nsymbols += bits[len];
  if (nsymbols < 1 || nsymbols > 256)
    ERREXIT(cinfo, JERR_BAD_HUFF_TABLE);

  MEMCOPY((*htblptr)->huffval, val, nsymbols * SIZEOF(UINT8));

  /* Initialize sent_table FALSE so table will be written to JPEG file. */
  (*htblptr)->sent_table = FALSE;
}


LOCAL(void)
std_huff_tables (j_compress_ptr cinfo)
/* Set up the standard Huffman tables (cf. JPEG standard section K.3) */
/* IMPORTANT: these are only valid for 8-bit data precision! */
{
  static const UINT8 bits_dc_luminance[17] =
    { /* 0-base */ 0, 0, 1, 5, 1, 1, 1, 1, 1, 1, 0, 0, 0, 0, 0, 0, 0 };
  static const UINT8 val_dc_luminance[] =
    { 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11 };
  
  static const UINT8 bits_dc_chrominance[17] =
    { /* 0-base */ 0, 0, 3, 1, 1, 1, 1, 1, 1, 1, 1, 1, 0, 0, 0, 0, 0 };
  static const UINT8 val_dc_chrominance[] =
    { 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11 };
  
  static const UINT8 bits_ac_luminance[17] =
    { /* 0-base */ 0, 0, 2, 1, 3, 3, 2, 4, 3, 5, 5, 4, 4, 0, 0, 1, 0x7d };
  static const UINT8 val_ac_luminance[] =
    { 0x01, 0x02, 0x03, 0x00, 0x04, 0x11, 0x05, 0x12,
      0x21, 0x31, 0x41, 0x06, 0x13, 0x51, 0x61, 0x07,
      0x22, 0x71, 0x14, 0x32, 0x81, 0x91, 0xa1, 0x08,
      0x23, 0x42, 0xb1, 0xc1, 0x15, 0x52, 0xd1, 0xf0,
      0x24, 0x33, 0x62, 0x72, 0x82, 0x09, 0x0a, 0x16,
      0x17, 0x18, 0x19, 0x1a, 0x25, 0x26, 0x27, 0x28,
      0x29, 0x2a, 0x34, 0x35, 0x36, 0x37, 0x38, 0x39,
      0x3a, 0x43, 0x44, 0x45, 0x46, 0x47, 0x48, 0x49,
      0x4a, 0x53, 0x54, 0x55, 0x56, 0x57, 0x58, 0x59,
      0x5a, 0x63, 0x64, 0x65, 0x66, 0x67, 0x68, 0x69,
      0x6a, 0x73, 0x74, 0x75, 0x76, 0x77, 0x78, 0x79,
      0x7a, 0x83, 0x84, 0x85, 0x86, 0x87, 0x88, 0x89,
      0x8a, 0x92, 0x93, 0x94, 0x95, 0x96, 0x97, 0x98,
      0x99, 0x9a, 0xa2, 0xa3, 0xa4, 0xa5, 0xa6, 0xa7,
      0xa8, 0xa9, 0xaa, 0xb2, 0xb3, 0xb4, 0xb5, 0xb6,