| 1 | \section{\module{imageop} ---
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| 2 | Manipulate raw image data}
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| 3 |
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| 4 | \declaremodule{builtin}{imageop}
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| 5 | \modulesynopsis{Manipulate raw image data.}
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| 6 |
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| 7 |
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| 8 | The \module{imageop} module contains some useful operations on images.
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| 9 | It operates on images consisting of 8 or 32 bit pixels stored in
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| 10 | Python strings. This is the same format as used by
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| 11 | \function{gl.lrectwrite()} and the \refmodule{imgfile} module.
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| 12 |
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| 13 | The module defines the following variables and functions:
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| 14 |
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| 15 | \begin{excdesc}{error}
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| 16 | This exception is raised on all errors, such as unknown number of bits
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| 17 | per pixel, etc.
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| 18 | \end{excdesc}
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| 19 |
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| 20 |
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| 21 | \begin{funcdesc}{crop}{image, psize, width, height, x0, y0, x1, y1}
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| 22 | Return the selected part of \var{image}, which should by
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| 23 | \var{width} by \var{height} in size and consist of pixels of
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| 24 | \var{psize} bytes. \var{x0}, \var{y0}, \var{x1} and \var{y1} are like
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| 25 | the \function{gl.lrectread()} parameters, i.e.\ the boundary is
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| 26 | included in the new image. The new boundaries need not be inside the
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| 27 | picture. Pixels that fall outside the old image will have their value
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| 28 | set to zero. If \var{x0} is bigger than \var{x1} the new image is
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| 29 | mirrored. The same holds for the y coordinates.
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| 30 | \end{funcdesc}
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| 31 |
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| 32 | \begin{funcdesc}{scale}{image, psize, width, height, newwidth, newheight}
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| 33 | Return \var{image} scaled to size \var{newwidth} by \var{newheight}.
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| 34 | No interpolation is done, scaling is done by simple-minded pixel
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| 35 | duplication or removal. Therefore, computer-generated images or
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| 36 | dithered images will not look nice after scaling.
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