Lib/test/test_imgfile.py

from test_support import verbose

import imgfile

     
def main():       

    testimage('test.rgb')
    testimage('greytest.rgb')


def testimage(name):
    """return a tuple consisting of
       image (in 'imgfile' format) width, height, size
    """

    import sys
    import os
    import string

    outputfile = '/tmp/deleteme'

    # try opening the name directly
    try:
	# This function returns a tuple (x, y, z) where x and y are the size of
	# the image in pixels and z is the number of bytes per pixel. Only
	# 3 byte RGB pixels and 1 byte greyscale pixels are supported.
	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))
    # This function reads and decodes the image on the specified file,
    # and returns it as a python string. The string has either 1 byte
    # greyscale pixels or 4 byte RGBA pixels. The bottom left pixel
    # is the first in the string. This format is suitable to pass
    # to gl.lrectwrite, for instance. 
    image = imgfile.read(name)
    
    # This function writes the RGB or greyscale data in data to
    # image file file. x and y give the size of the image, z is
    # 1 for 1 byte greyscale images or 3 for RGB images (which
    # are stored as 4 byte values of which only the lower three
    # bytes are used). These are the formats returned by gl.lrectread. 
    if verbose:
	print 'Writing output file'
    imgfile.write (outputfile, image, sizes[0], sizes[1], sizes[2]) 
   

    if verbose:
	print 'Opening scaled test image: %s, sizes: %s' % (name, str(sizes))
    # This function is identical to read but it returns an image that
    # is scaled to the given x and y sizes. If the filter and blur
    # parameters are omitted scaling is done by simply dropping
    # or duplicating pixels, so the result will be less than perfect,
    # especially for computer-generated images.  Alternatively,
    # you can specify a filter to use to smoothen the image after
    # scaling. The filter forms supported are 'impulse', 'box',
    # 'triangle', 'quadratic' and 'gaussian'. If a filter is
    # specified blur is an optional parameter specifying the
    # blurriness of the filter. It defaults to 1.0.  readscaled
    # makes no attempt to keep the aspect ratio correct, so that
    # is the users' responsibility.
    if verbose:
	print 'Filtering with "impulse"'
    simage = imgfile.readscaled (name, sizes[0]/2, sizes[1]/2, 'impulse', 2.0)

    # This function sets a global flag which defines whether the
    # scan lines of the image are read or written from bottom to
    # top (flag is zero, compatible with SGI GL) or from top to
    # bottom(flag is one, compatible with X). The default is zero. 
    if verbose:
	print 'Switching to X compatibility'
    imgfile.ttob (1) 

    if verbose:
	print 'Filtering with "triangle"'
    simage = imgfile.readscaled (name, sizes[0]/2, sizes[1]/2, 'triangle', 3.0)
    if verbose:
	print 'Switching back to SGI compatibility'
    imgfile.ttob (0) 
    
    if verbose: print 'Filtering with "quadratic"'
    simage = imgfile.readscaled (name, sizes[0]/2, sizes[1]/2, 'quadratic')
    if verbose: print 'Filtering with "gaussian"'
    simage = imgfile.readscaled (name, sizes[0]/2, sizes[1]/2, 'gaussian', 1.0)

    if verbose:
	print 'Writing output file'
    imgfile.write (outputfile, simage, sizes[0]/2, sizes[1]/2, sizes[2]) 

    os.unlink(outputfile)

main()