1 2 :mod:`imageop` --- Manipulate raw image data 3 ============================================ 4 5 .. module:: imageop 6 :synopsis: Manipulate raw image data. 7 :deprecated: 8 9 .. deprecated:: 2.6 10 The :mod:`imageop` module has been removed in Python 3. 11 12 The :mod:`imageop` module contains some useful operations on images. It operates 13 on images consisting of 8 or 32 bit pixels stored in Python strings. This is 14 the same format as used by :func:`gl.lrectwrite` and the :mod:`imgfile` module. 15 16 The module defines the following variables and functions: 17 18 19 .. exception:: error 20 21 This exception is raised on all errors, such as unknown number of bits per 22 pixel, etc. 23 24 25 .. function:: crop(image, psize, width, height, x0, y0, x1, y1) 26 27 Return the selected part of *image*, which should be *width* by *height* in size 28 and consist of pixels of *psize* bytes. *x0*, *y0*, *x1* and *y1* are like the 29 :func:`gl.lrectread` parameters, i.e. the boundary is included in the new image. 30 The new boundaries need not be inside the picture. Pixels that fall outside the 31 old image will have their value set to zero. If *x0* is bigger than *x1* the 32 new image is mirrored. The same holds for the y coordinates. 33 34 35 .. function:: scale(image, psize, width, height, newwidth, newheight) 36 37 Return *image* scaled to size *newwidth* by *newheight*. No interpolation is 38 done, scaling is done by simple-minded pixel duplication or removal. Therefore, 39 computer-generated images or dithered images will not look nice after scaling. 40 41 42 .. function:: tovideo(image, psize, width, height) 43 44 Run a vertical low-pass filter over an image. It does so by computing each 45 destination pixel as the average of two vertically-aligned source pixels. The 46 main use of this routine is to forestall excessive flicker if the image is 47 displayed on a video device that uses interlacing, hence the name. 48 49 50 .. function:: grey2mono(image, width, height, threshold) 51 52 Convert an 8-bit deep greyscale image to a 1-bit deep image by thresholding all 53 the pixels. The resulting image is tightly packed and is probably only useful 54 as an argument to :func:`mono2grey`. 55 56 57 .. function:: dither2mono(image, width, height) 58 59 Convert an 8-bit greyscale image to a 1-bit monochrome image using a 60 (simple-minded) dithering algorithm. 61 62 63 .. function:: mono2grey(image, width, height, p0, p1) 64 65 Convert a 1-bit monochrome image to an 8 bit greyscale or color image. All 66 pixels that are zero-valued on input get value *p0* on output and all one-value 67 input pixels get value *p1* on output. To convert a monochrome black-and-white 68 image to greyscale pass the values ``0`` and ``255`` respectively. 69 70 71 .. function:: grey2grey4(image, width, height) 72 73 Convert an 8-bit greyscale image to a 4-bit greyscale image without dithering. 74 75 76 .. function:: grey2grey2(image, width, height) 77 78 Convert an 8-bit greyscale image to a 2-bit greyscale image without dithering. 79 80 81 .. function:: dither2grey2(image, width, height) 82 83 Convert an 8-bit greyscale image to a 2-bit greyscale image with dithering. As 84 for :func:`dither2mono`, the dithering algorithm is currently very simple. 85 86 87 .. function:: grey42grey(image, width, height) 88 89 Convert a 4-bit greyscale image to an 8-bit greyscale image. 90 91 92 .. function:: grey22grey(image, width, height) 93 94 Convert a 2-bit greyscale image to an 8-bit greyscale image. 95 96 97 .. data:: backward_compatible 98 99 If set to 0, the functions in this module use a non-backward compatible way 100 of representing multi-byte pixels on little-endian systems. The SGI for 101 which this module was originally written is a big-endian system, so setting 102 this variable will have no effect. However, the code wasn't originally 103 intended to run on anything else, so it made assumptions about byte order 104 which are not universal. Setting this variable to 0 will cause the byte 105 order to be reversed on little-endian systems, so that it then is the same as 106 on big-endian systems. 107 108
