On 30 December 2009 pm 11:07:18 da.mihi.sis.bubulae.frustrum.assae.solana.tuberosa.in.modo.gallico.fricta.ac.quassum.lactatum.coagulatum.cras...@imagemagick.org wrote: > > but as far as I can tell both images are identical. > > One has an alpha channel, the other does not: > > -> compare +matte -metric rmse external.png external-crushed.png null: > 0 (0)
Thanks, that worked for these 2 images. But hmm, doesn't adding the +matte switch makes the comparison less generic? I do have a few pngs with transparency enabled, for which I would need to compare both rgb data and alpha data to ensure everything is still identical. Is there a set of arguments I could use to do a generic comparison in all cases? Reading on the -channel switch, it seems I should turn "-alpha on" which creates an opaque alpha channel if its not in an image, but that didn't work for these 2 images :(. "-alpha set" did work though. For these 2 images anyway, I don't understand how the alpha channel is set in the first image. I thought that even though there is alpha data, it was fully opaque. In gimp if I push a plain red layer underneath for example, there's no color change so the icon is fully opaque, which is why I guess the png crusher (pngout) dropped it in the optimized image. Sorry I'm kind of new to this, how would I go about checking out the actual structure of the first non-optimized image? Thanks! Tim. _______________________________________________ Magick-users mailing list [email protected] http://studio.imagemagick.org/mailman/listinfo/magick-users
