Lib/test/test_imageop.py

#! /usr/bin/env python
"""Test script for the imageop module.  This has the side
   effect of partially testing the imgfile module as well.
   Roger E. Masse
"""
from test_support import verbose

import imageop

def main():
    
    image, width, height = getimage('test.rgb')

    # Return the selected part of image, which should by width by height
    # in size and consist of pixels of psize bytes.
    if verbose:
	print 'crop'
    newimage = imageop.crop (image, 4, width, height, 0, 0, 1, 1)

    # 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. 
    if verbose:
	print 'scale'
    scaleimage = imageop.scale(image, 4, width, height, 1, 1)

    # 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 two vertically-aligned source pixels,  hence the name. 
    if verbose:
	print 'tovideo'
    videoimage = imageop.tovideo (image, 4, width, height)
    
    image, width, height = getimage('greytest.rgb')  
    # Convert a 8-bit deep greyscale image to a 1-bit deep image by
    # tresholding all the pixels. The resulting image is tightly packed
    # and is probably only useful as an argument to mono2grey. 
    if verbose:
	print 'grey2mono'
    monoimage = imageop.grey2mono (image, width, height, 0) 

    #monoimage, width, height = getimage('monotest.rgb')

    # 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.
    if verbose:
	print 'mono2grey'
    greyimage = imageop.mono2grey (monoimage, width, height, 0, 255)

    # Convert an 8-bit greyscale image to a 1-bit monochrome image using a
    # (simple-minded) dithering algorithm.
    if verbose:
	print 'dither2mono'
    monoimage = imageop.dither2mono (greyimage, width, height)


    # Convert an 8-bit greyscale image to a 4-bit greyscale image without
    # dithering. 
    if verbose:
	print 'grey2grey4'
    grey4image = imageop.grey2grey4 (greyimage, width, height) 

    # Convert an 8-bit greyscale image to a 2-bit greyscale image without
    # dithering. 
    if verbose:
	print 'grey2grey2'
    grey2image = imageop.grey2grey2 (greyimage, width, height) 

    # Convert an 8-bit greyscale image to a 2-bit greyscale image with
    # dithering. As for dither2mono, the dithering algorithm is currently
    # very simple. 
    if verbose:
	print 'dither2grey2'
    grey2image = imageop.dither2grey2 (greyimage, width, height) 

    # Convert a 4-bit greyscale image to an 8-bit greyscale image. 
    if verbose:
	print 'grey42grey'
    greyimage = imageop.grey42grey (grey4image, width, height) 

    # Convert a 2-bit greyscale image to an 8-bit greyscale image. 
    if verbose:
	print 'grey22grey'
    image = imageop.grey22grey (grey2image, width, height) 

def getimage(name):
    """return a tuple consisting of
       image (in 'imgfile' format) width and height
    """

    import sys
    import os
    import imgfile
    import string

    # try opening the name directly
    try:
	sizes = imgfile.getsizes(name)
    except imgfile.error:
	# get a more qualified path component of the script...
	if __name__ == '__main__':
	    ourname = sys.argv[0]
	else: # ...or the full path of the module
	    ourname = sys.modules[__name__].__file__

	parts = string.splitfields(ourname, os.sep)
	parts[-1] = name
	name = string.joinfields(parts, os.sep)
	sizes = imgfile.getsizes(name)
    if verbose:
	print 'Opening test image: %s, sizes: %s' % (name, str(sizes))

    image = imgfile.read(name)
    return (image, sizes[0], sizes[1])

main()