Here's an example regarding the image color quantization I've been talking about.
This is an original subtitle bitmap having a palette of 4 or 5 colors:
fate-suite\apng\o_sample.png
All following images are zoomed to 400% and taken as screenshots from Photoshop
ffmpeg -y -loglevel verbose -i "fate-suite\apng\o_sample.png" -filter_complex "split[split1][split2];[split1]palettegen=max_colors=255:use_alpha=1[pal1];[split2][pal1]paletteuse=use_alpha=1" -frames:v 1 out.png
ffmpeg -y -loglevel verbose -i "fate-suite\apng\o_sample.png" -filter_complex "split[split1][split2];[split1]palettegen=max_colors=255[pal1];[split2][pal1]paletteuse" -frames:v 1 out.png
ffmpeg -y -loglevel verbose -i "..\fate-suite\apng\o_sample.png" -filter_complex "elbg=pal8=1" -frames:v 1 out.png
ffmpeg -y -loglevel verbose -i "..\fate-suite\apng\o_sample.png" -filter_complex "elbg=pal8=1:use_alpha=1" -frames:v 1 out.png
Palettized via palettegen and palleteuse (8 colors max):
Palettized via Photoshop (8 colors max):
Palettized via palettegen and palleteuse after adding alpha support (8 colors max):
via elbg with the new alpha patch
via palettegen and palleteuse (8 colors max): - 200% magnified
Palettized via Photoshop max):: - 200% magnified
via palettegen and palleteuse after adding alpha support (8 colors max): - 200% magnified
via elbg with the new alpha patch