Hi! A few weeks ago dithering was added to Rawspeed, as part of the bit scaling process. Rawspeed delivers 16 bit images, so for images that are scaled from 12 to 16 bit, the "new" 4 bits now contain noise instead of "0" (or any other fixed value). I don't know when or if darktable has been updated with this code.
I think the only case where dithering isn't applied is some compressed Nikon formats that contain values compressed with a fixed tone curve, but other than that you should get automatic dithering on all images already. Regards, Klaus Post http://www.klauspost.com On Wed, Dec 26, 2012 at 6:04 PM, Ulrich Pegelow <[email protected] > wrote: > Hi guys, > > you might have observed that some of our modules can produce banding > artifacts. Main candidates are vignetting and graduated neutral density. > There are certainly other situations as well where banding might hit you. > > It was easy to add a dithering option to vignetting by adding some > random noise. > > Graduated neutral density on the other hand is problematic as it comes > very early in pixelpipe. Any added random noise will scale in an > unpredictable way and there are some modules after gnd that will do > their best to eliminate noise again... > > For that reason I developed a general dithering module which comes late > in pixelpipe, just before gamma. It supports random dither and error > diffusion (Floyd-Steinberg). The latter with just a few output options. > I left some room for future enhancements. Namely one could think about > dithering into a user-defined color palette and such. > > With dithering there is some inherent issue when you scale the image. > Rendering a scaled-down version into 1-bit b&w would look completely > different than seeing the same image dithered with original resolution > from some distance. I did a few tricks with dithering levels in order to > make zooming halfways intuitive. > > All is kept in a separate branch 'dither'. Please give it a try, tell me > your feedback and vote if you think this should move into master. > > Ulrich > > > ------------------------------------------------------------------------------ > LogMeIn Rescue: Anywhere, Anytime Remote support for IT. Free Trial > Remotely access PCs and mobile devices and provide instant support > Improve your efficiency, and focus on delivering more value-add services > Discover what IT Professionals Know. Rescue delivers > http://p.sf.net/sfu/logmein_12329d2d > _______________________________________________ > darktable-devel mailing list > [email protected] > https://lists.sourceforge.net/lists/listinfo/darktable-devel >
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