symbian-qemu-0.9.1-12/python-2.6.1/Doc/library/imageop.rst
author johnathan.white@2718R8BGH51.accenture.com
Mon, 08 Mar 2010 18:45:03 +0000
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parent 1 2fb8b9db1c86
permissions -rw-r--r--
Modify framebuffer and NGA framebuffer to read screen size from board model dtb file. Optimise memory usuage of frame buffer Add example minigui application with hooks to profiler (which writes results to S:\). Modified NGA framebuffer to run its own dfc queue at high priority
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:mod:`imageop` --- Manipulate raw image data
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============================================
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.. module:: imageop
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   :synopsis: Manipulate raw image data.
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   :deprecated:
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.. deprecated:: 2.6
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    The :mod:`imageop` module has been removed in Python 3.0.
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The :mod:`imageop` module contains some useful operations on images. It operates
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on images consisting of 8 or 32 bit pixels stored in Python strings.  This is
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the same format as used by :func:`gl.lrectwrite` and the :mod:`imgfile` module.
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The module defines the following variables and functions:
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.. exception:: error
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   This exception is raised on all errors, such as unknown number of bits per
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   pixel, etc.
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.. function:: crop(image, psize, width, height, x0, y0, x1, y1)
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   Return the selected part of *image*, which should be *width* by *height* in size
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   and consist of pixels of *psize* bytes. *x0*, *y0*, *x1* and *y1* are like the
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   :func:`gl.lrectread` parameters, i.e. the boundary is included in the new image.
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   The new boundaries need not be inside the picture.  Pixels that fall outside the
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   old image will have their value set to zero.  If *x0* is bigger than *x1* the
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   new image is mirrored.  The same holds for the y coordinates.
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.. function:: scale(image, psize, width, height, newwidth, newheight)
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   Return *image* scaled to size *newwidth* by *newheight*. No interpolation is
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   done, scaling is done by simple-minded pixel duplication or removal.  Therefore,
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   computer-generated images or dithered images will not look nice after scaling.
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.. function:: tovideo(image, psize, width, height)
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   Run a vertical low-pass filter over an image.  It does so by computing each
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   destination pixel as the average of two vertically-aligned source pixels.  The
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   main use of this routine is to forestall excessive flicker if the image is
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   displayed on a video device that uses interlacing, hence the name.
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.. function:: grey2mono(image, width, height, threshold)
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   Convert a 8-bit deep greyscale image to a 1-bit deep image by thresholding all
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   the pixels.  The resulting image is tightly packed and is probably only useful
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   as an argument to :func:`mono2grey`.
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.. function:: dither2mono(image, width, height)
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   Convert an 8-bit greyscale image to a 1-bit monochrome image using a
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   (simple-minded) dithering algorithm.
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.. function:: mono2grey(image, width, height, p0, p1)
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   Convert a 1-bit monochrome image to an 8 bit greyscale or color image. All
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   pixels that are zero-valued on input get value *p0* on output and all one-value
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   input pixels get value *p1* on output.  To convert a monochrome black-and-white
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   image to greyscale pass the values ``0`` and ``255`` respectively.
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.. function:: grey2grey4(image, width, height)
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   Convert an 8-bit greyscale image to a 4-bit greyscale image without dithering.
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.. function:: grey2grey2(image, width, height)
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   Convert an 8-bit greyscale image to a 2-bit greyscale image without dithering.
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.. function:: dither2grey2(image, width, height)
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   Convert an 8-bit greyscale image to a 2-bit greyscale image with dithering.  As
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   for :func:`dither2mono`, the dithering algorithm is currently very simple.
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.. function:: grey42grey(image, width, height)
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   Convert a 4-bit greyscale image to an 8-bit greyscale image.
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.. function:: grey22grey(image, width, height)
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   Convert a 2-bit greyscale image to an 8-bit greyscale image.
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.. data:: backward_compatible
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   If set to 0, the functions in this module use a non-backward compatible way
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   of representing multi-byte pixels on little-endian systems.  The SGI for
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   which this module was originally written is a big-endian system, so setting
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   this variable will have no effect. However, the code wasn't originally
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   intended to run on anything else, so it made assumptions about byte order
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   which are not universal.  Setting this variable to 0 will cause the byte
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   order to be reversed on little-endian systems, so that it then is the same as
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   on big-endian systems.
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