2019-04-07 2:17 GMT+02:00, Mikhail V <mikhail...@gmail.com>: > I have a strange problem with extracting alpha plane from an grayscale > PNG with alpha channel. > So I have an image with alpha in it and use this command: > > ffmpeg -i 1-open-patch.png -vf alphaextract -pix_fmt gray > testgray_alpha.png > or > ffmpeg -i 1-open-patch.png -vf alphaextract testgray_alpha.png > (wich works same way I think) > > Problem: the output alpha plane is shifted 1 pixel to the left. The > data is ok - but the position is 1 pixel shifted. > The problem appears only with ya8 pixel format. If I use same but RGBa > image the output plane is correctly positioned.
Please test the inlined patch. Carl Eugen diff --git a/libavfilter/vf_extractplanes.c b/libavfilter/vf_extractplanes.c index 739c242..2f2c8e1 100644 --- a/libavfilter/vf_extractplanes.c +++ b/libavfilter/vf_extractplanes.c @@ -226,6 +226,8 @@ static int config_input(AVFilterLink *inlink) for (i = 0; i < 4; i++) s->map[i] = rgba_map[s->map[i]]; } + if (inlink->format == AV_PIX_FMT_GRAY8A) + s->map[0] = 1; return 0; } _______________________________________________ ffmpeg-user mailing list ffmpeg-user@ffmpeg.org https://ffmpeg.org/mailman/listinfo/ffmpeg-user To unsubscribe, visit link above, or email ffmpeg-user-requ...@ffmpeg.org with subject "unsubscribe".