On Fri, Sep 24, 2021 at 10:30:31AM +0000, Soft Works wrote: > Hi, > > for a new filter, I want to rescale PAL8 subtitle bitmaps where the palette > includes > colors with alpha. > > From what I’ve seen, swscale doesn’t support PAL8-to-PAL8, only PAL8-to-BGR8 > which doesn’t support alpha and the palette is fixed with 256 entries defined > by > convention, while I would ideally like to be able to allow the following: > > - constrain the output to use the same palette as the input > - adaptively quantize it to a palette with a configurable number of colors > > Thus it's about the palette quantization (with or without dithering) after > scaling in RGBA. (or some cool algorithmic trick I'm not aware of) > > Is there any existing code that I could reuse? The closest I could find > is pngenc, but I'm wondering whether there's something else/better > somewhere in the ffmpeg libs that I haven't seen?
There are some non linear scaling filters which may make sense when you do not have the full linear space available see: hqx, epx, xbr you could also try some neural net stuff or the insane solution, OCR, scale text, render font into RGBA and then back to PAL8 thx [...] -- Michael GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB Those who are best at talking, realize last or never when they are wrong.
signature.asc
Description: PGP signature
_______________________________________________ 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".
