A method and apparatus are disclosed for testing the accuracy of digital
test images generated by a computer graphics program executed on a
computer graphics system. A test program is utilized to compare a test
image with a reference image. Regional image quantification verification
aims at an image comparison test that accepts minor color value
differences and spatial shifts in rendered pixel values. The test image
and reference image are divided into corresponding sub-regions. The
average color value for each sub-region of the test image is compared to
the average color value of the corresponding reference image sub-region
and also to other nearby reference image sub-regions. A test image is
unacceptably different from a reference image, if for any sub-region of
the test image, no reference image sub-region is found with an average
color value difference and spatial shift less than specified maximums.