/Doc/library/imageop.rst
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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.