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+
+:mod:`imageop` --- Manipulate raw image data
+============================================
+
+.. module:: imageop
+ :synopsis: Manipulate raw image data.
+ :deprecated:
+
+.. deprecated:: 2.6
+ The :mod:`imageop` module has been removed in Python 3.0.
+
+The :mod:`imageop` module contains some useful operations on images. It operates
+on images consisting of 8 or 32 bit pixels stored in Python strings. This is
+the same format as used by :func:`gl.lrectwrite` and the :mod:`imgfile` module.
+
+The module defines the following variables and functions:
+
+
+.. exception:: error
+
+ This exception is raised on all errors, such as unknown number of bits per
+ pixel, etc.
+
+
+.. function:: crop(image, psize, width, height, x0, y0, x1, y1)
+
+ Return the selected part of *image*, which should be *width* by *height* in size
+ and consist of pixels of *psize* bytes. *x0*, *y0*, *x1* and *y1* are like the
+ :func:`gl.lrectread` parameters, i.e. the boundary is included in the new image.
+ The new boundaries need not be inside the picture. Pixels that fall outside the
+ old image will have their value set to zero. If *x0* is bigger than *x1* the
+ new image is mirrored. The same holds for the y coordinates.
+
+
+.. function:: scale(image, psize, width, height, newwidth, newheight)
+
+ Return *image* scaled to size *newwidth* by *newheight*. No interpolation is
+ done, scaling is done by simple-minded pixel duplication or removal. Therefore,
+ computer-generated images or dithered images will not look nice after scaling.
+
+
+.. function:: tovideo(image, psize, width, height)
+
+ Run a vertical low-pass filter over an image. It does so by computing each
+ destination pixel as the average of two vertically-aligned source pixels. The
+ main use of this routine is to forestall excessive flicker if the image is
+ displayed on a video device that uses interlacing, hence the name.
+
+
+.. function:: grey2mono(image, width, height, threshold)
+
+ Convert a 8-bit deep greyscale image to a 1-bit deep image by thresholding all
+ the pixels. The resulting image is tightly packed and is probably only useful
+ as an argument to :func:`mono2grey`.
+
+
+.. function:: dither2mono(image, width, height)
+
+ Convert an 8-bit greyscale image to a 1-bit monochrome image using a
+ (simple-minded) dithering algorithm.
+
+
+.. function:: mono2grey(image, width, height, p0, p1)
+
+ Convert a 1-bit monochrome image to an 8 bit greyscale or color image. All
+ pixels that are zero-valued on input get value *p0* on output and all one-value
+ input pixels get value *p1* on output. To convert a monochrome black-and-white
+ image to greyscale pass the values ``0`` and ``255`` respectively.
+
+
+.. function:: grey2grey4(image, width, height)
+
+ Convert an 8-bit greyscale image to a 4-bit greyscale image without dithering.
+
+
+.. function:: grey2grey2(image, width, height)
+
+ Convert an 8-bit greyscale image to a 2-bit greyscale image without dithering.
+
+
+.. function:: dither2grey2(image, width, height)
+
+ Convert an 8-bit greyscale image to a 2-bit greyscale image with dithering. As
+ for :func:`dither2mono`, the dithering algorithm is currently very simple.
+
+
+.. function:: grey42grey(image, width, height)
+
+ Convert a 4-bit greyscale image to an 8-bit greyscale image.
+
+
+.. function:: grey22grey(image, width, height)
+
+ Convert a 2-bit greyscale image to an 8-bit greyscale image.
+
+
+.. data:: backward_compatible
+
+ If set to 0, the functions in this module use a non-backward compatible way
+ of representing multi-byte pixels on little-endian systems. The SGI for
+ which this module was originally written is a big-endian system, so setting
+ this variable will have no effect. However, the code wasn't originally
+ intended to run on anything else, so it made assumptions about byte order
+ which are not universal. Setting this variable to 0 will cause the byte
+ order to be reversed on little-endian systems, so that it then is the same as
+ on big-endian systems.
+