Hi there, I'm in a process of doing some png crushing on a whole bunch of images. To be extra sure the crushing is lossless, I thought I could run compare on the original versus optimized. That works great in most cases, except I am hitting a few false negatives, could anyone confirm with me if it is a bug or if I am doing something wrong?
Two such images are here (very small 12x12 icons): http://timotheegroleau.com/tmp/external.png (~46kb) http://timotheegroleau.com/tmp/external-crushed.png (114b) To check that my images are identical or not, I run compare (from IM-6.5.8-8 under gentoo) like so: compare -dissimilarity-threshold 1 -metric AE original.png crushed.png /dev/null 2>&1 and read the result. If it is 0, images are identical; not zero, some pixels differ. For the 2 pics above, I get a result of 84, but as far as I can tell both images are identical. The difference image that compare generates shows a whole bunch of pixels supposedly different, but I just cannot see them in the original versus optimized (I'm using gimp to zoom in and check). The original png is grossly uncompressed, the crushed image is super optimized with a 2-color palette. The false negative makes me wonder if there are false positives too, so I am worried on the reliability of my validation with compare. Any help would be much appreciated. Many thanks! Tim. _______________________________________________ Magick-users mailing list [email protected] http://studio.imagemagick.org/mailman/listinfo/magick-users
