magick wrote:Pixel differences between these two images are isolated to fully transparent pixels. The AbsoluteError metric notes any differences in pixel colors, however, fully transparent pixels are considered equivalent. In this case, fully transparent white is equivalent to fully transparent black. The AbsoluteError metric is sensitive to the -fuzz option. We could patch the algorithm to consider fully transparent black as different from fully transparent white, but we'll need Anthony's opinion before we can implement the change.
NO. The point of AE is that the images are the same! Full-transparent pixels have undefined colors, and AE reflects this when other metrics do not.
More that likely AE comes out a 'idenitical' is that for the partial transparent pixel is that it is so close to transparent the rounding effects make them equivelent. I saw similar almost fully transparent pixel in another image. and in a 8 bit depth they probably are fully transparent. But as they were not quite fully-transparent, and they did not have the 'right' color, thouse pixel causes lots of problems.
Simple way to find them is use
-background white -alpha background -alpha off This sets all fully-transparent pixels to white, then turns alpha off. The result is that any badly colored 'black' pixels are now highlighted, as they will still be black, when all other pixels are now very bright.
For other methods, see IM Examples, Compare
http://www.imagemagick.org/Usage/compare/
If you know what program generated these bad (almost transparent) pixels. Please let us know.
