There have been many changes to PNG encoder and many other areas. Latest version at the moment is 6.6.7-7, latest version in Portage is 6.6.5.6. Reproducible: Always Steps to Reproduce:
It's not good idea to bump to *latest* ImageMagick tarball because upstream tends to change the tarball after it's been released. So I've bumped it to 6.6.7.6 instead: +*imagemagick-6.6.7.6 (15 Feb 2011) + + 15 Feb 2011; Samuli Suominen <ssuominen@gentoo.org> + +imagemagick-6.6.7.6.ebuild: + Version bump wrt #354945 by "Lypsik".