Re: [FFmpeg-devel] [PATCH v2 01/32] avfilter/palettegen: allow a minimum of 2 colors
ons 2022-12-28 klockan 22:23 +0100 skrev Clément Bœsch: > On Wed, Dec 28, 2022 at 10:04:26PM +0100, Tomas Härdin wrote: > [...] > > Does this mean all-black with transparent is disallowed? > > Yes a single color with or without an extra transparency slot makes > no > sense. > > > Shouldn't it be max_colors + reserve < 2? > > max_colors accounts for the transparent color as well. So if you > specify > 256 colors with reserve_transparent (default settings), you'll get > 255 > color slots and 1 for transparency. > > It also means that if want to go as low as 2 colors in your palette > you > can do max_colors=3 with reserve_transparent=1, or max_colors=2 with > reserve_transparent=0 > > 3-1 → 2 > 2-0 → 2 > > These are the minimums. Right, because there's no "0bpp" pixel format with 1bpp alpha.. yet! Something similar actually exists with GoldSrc .spr files, especially the indexalpha mode. It is effectively "0bpp" with 8-bit alpha: https://the303.org/tutorials/gold_sprite_p3.htm > > PS: sorry for the double answer Tomas! No problem :) /Tomas ___ 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".
Re: [FFmpeg-devel] [PATCH v2 01/32] avfilter/palettegen: allow a minimum of 2 colors
On Wed, Dec 28, 2022 at 10:04:26PM +0100, Tomas Härdin wrote: [...] > Does this mean all-black with transparent is disallowed? Yes a single color with or without an extra transparency slot makes no sense. > Shouldn't it be max_colors + reserve < 2? max_colors accounts for the transparent color as well. So if you specify 256 colors with reserve_transparent (default settings), you'll get 255 color slots and 1 for transparency. It also means that if want to go as low as 2 colors in your palette you can do max_colors=3 with reserve_transparent=1, or max_colors=2 with reserve_transparent=0 3-1 → 2 2-0 → 2 These are the minimums. PS: sorry for the double answer Tomas! -- 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".
Re: [FFmpeg-devel] [PATCH v2 01/32] avfilter/palettegen: allow a minimum of 2 colors
ons 2022-12-28 klockan 00:17 +0100 skrev Clément Bœsch:
> ---
> libavfilter/vf_palettegen.c | 7 ++-
> 1 file changed, 6 insertions(+), 1 deletion(-)
>
> diff --git a/libavfilter/vf_palettegen.c
> b/libavfilter/vf_palettegen.c
> index 27f74fd147..c03f62b942 100644
> --- a/libavfilter/vf_palettegen.c
> +++ b/libavfilter/vf_palettegen.c
> @@ -82,7 +82,7 @@ typedef struct PaletteGenContext {
> #define OFFSET(x) offsetof(PaletteGenContext, x)
> #define FLAGS AV_OPT_FLAG_FILTERING_PARAM|AV_OPT_FLAG_VIDEO_PARAM
> static const AVOption palettegen_options[] = {
> - { "max_colors", "set the maximum number of colors to use in the
> palette", OFFSET(max_colors), AV_OPT_TYPE_INT, {.i64=256}, 4, 256,
> FLAGS },
> + { "max_colors", "set the maximum number of colors to use in the
> palette", OFFSET(max_colors), AV_OPT_TYPE_INT, {.i64=256}, 2, 256,
> FLAGS },
> { "reserve_transparent", "reserve a palette entry for
> transparency", OFFSET(reserve_transparent), AV_OPT_TYPE_BOOL,
> {.i64=1}, 0, 1, FLAGS },
> { "transparency_color", "set a background color for
> transparency", OFFSET(transparency_color), AV_OPT_TYPE_COLOR,
> {.str="lime"}, 0, 0, FLAGS },
> { "stats_mode", "set statistics mode", OFFSET(stats_mode),
> AV_OPT_TYPE_INT, {.i64=STATS_MODE_ALL_FRAMES}, 0, NB_STATS_MODE-1,
> FLAGS, "mode" },
> @@ -586,6 +586,11 @@ static int init(AVFilterContext *ctx)
> if (s->use_alpha && s->reserve_transparent)
> s->reserve_transparent = 0;
>
> + if (s->max_colors - s->reserve_transparent < 2) {
> + av_log(ctx, AV_LOG_ERROR, "max_colors=2 is only allowed
> without reserving a transparent color slot\n");
Does this mean all-black with transparent is disallowed? Shouldn't it
be max_colors + reserve < 2?
/Tomas
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