Hi, This patchset essentially fixes a few core problems in these filters and switches to a perceptual model.
I've generated a report for each key commit on this (temporary) page: http://big.pkh.me/pal/ (warning: heavy page, ~500M; I did try to add some lazy loading of the images but I'm not sure it's actually working as expected). It is easy for me to add specific samples and re-run the whole thing, so feel free to suggest one. A summary on a few important observed differences can be found on the page, but I'm duplicating it here for the record: - Current: current state on master - Paletteuse Perceptual + same palette but better selection: instead of rgb triplet distance, it uses a colorspace designed for uniform perceptual color differences (OkLab) + overall impact not that visible immediately, but it will make sure the palette is used the best way possible, meaning improvements to palettegen will be honored + observations (with no dither): * file02 (rooftops) in max_colors=8 or 16: sky pattern is more stable * file06 (parrot) in max_colors=8: better color for the parrot beak * overall seems to favor slightly brighter colors in the currently offered palette - Palettegen Linear Average + sRGB colors are gamma encoded, averaging them naively is incorrect, we need to do that in linear space + observations (with no dither): * file00 (colorful drawing) in max_colors=8: contrast and color skin look better * file07 (abstract flower) in max_color=128 or 256: this picture composed of 1M different colors in the source is now more balanced (better spreading of the colors) - Palettegen Perceptual + similar to the paletteuse perceptual, we use OkLab for the color distance + observations (with no dither): * file07 (abstract flower): in max_colors=128 or 256 we can see the picture offering a much finer grain. - Palettegen Variance per axis + When deciding on spliting a box along an axis, instead of picking the longest one, we pick the one with the most color variance + Not that much impact Overall, the most brutal change is probably in file07 between current and last, 256 colors no dither in particular. Finally, I do believe a lot of other color filters could at least benefit from fixing their gamma handling (I know I'm guilty of this in various other filters). Regards, -- Clément B. _______________________________________________ ffmpeg-devel mailing list ffmpeg-devel@ffmpeg.org https://ffmpeg.org/mailman/listinfo/ffmpeg-devel To unsubscribe, visit link above, or email ffmpeg-devel-requ...@ffmpeg.org with subject "unsubscribe".
