From Bugzilla Helper: User-Agent: Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.0.0) Gecko/20020605 Description of problem: gdk-pixbuf currently does not dither images in 16bpp; visible banding occurs. Version-Release number of selected component (if applicable): How reproducible: Always Steps to Reproduce: 1. View images used in GTK+ widgets. 2. Horrible banding occurs on gradients and alpha gradients. Expected Results: Images displayed using GTK+2, such as those in Anaconda, up2date, etc. should look fine in 16bpp, with no banding. Dithering would make things look "normal". Additional info:
It's not at all clear to me that changing 16bpp to dither at GTK_DITHER_NORMAL level would be a compatible change... note also in many cases the problem is that rendering is going through the alpha-composited path, which can never be dithered.
Marking various no-need-to-be-private bugs public.
I think Owen is right. The docs for GdkRgbDither clearly define that GDK_RGB_DITHER_NORMAL doesn't dither at 16bpp. This must be fixed in the caller by using GDK_RGB_DITHER_MAX. I don't know how anaconda displays its images...