On Tue, Jan 31, 2012 at 06:25:14PM +0100, Bogdan Szczurek wrote: > W dniu 12-01-31 15:48, gespertino@xxxxxxxxx pisze: > >Here I have to quote my friend Troy Sobotka who's usually a jerk towards > >GIMP :-p but makes a point: > >http://troy-sobotka.blogspot.com/2011/01/bit-depth-and-confusion.html > > As much as I agree with general idea I want to point out two things > about image comparing 8 bit dithered and 15 bit outputs (the square > regions). My point was to show the dithering noise that I got rid of by switching from 8bpc to 15bpc. It wasn't really meant for scientific analysis ;-) > First: they're not of the same dynamic range. The upper one is "brighter", > "wider" Well, I just opened both MyPaint versions and painted roughly the same (large) number of circles with a faint brush. The right box is a magnification of the left box (which is a section of the full circle). > and "not grayscale" like the bottom one. It makes its "ugliness" more > apparent. Both images were made with a pure black brush painting over pure white. The color that you see comes from the dithering. I used a different random number to dither each color channel. This actually improves the perceived smoothness of the result. > Second: why to use dithering anyway since internally you're using sRGB, > monitor "should be" at least sRGB?… Do you have any other examples maybe? Dithering was done per dab. When you stamp a dab, 8bpc over 8bpc, you get a 16bpc intermediate result. When scaling this back to 8bpc I used dithering instead of simple rounding. If I had done rounding, I would have gotten banding instead of noise. Same problem, different manifestation. -- Martin Renold _______________________________________________ gimp-developer-list mailing list gimp-developer-list@xxxxxxxxx http://mail.gnome.org/mailman/listinfo/gimp-developer-list
