Currently restricted to blending pixels that only contain either
0 or 255 in their alpha components
Signed-off-by: Donny Yang <w...@kota.moe>
---
libavcodec/pngdec.c | 15 ++++++++++++++-
1 file changed, 14 insertions(+), 1 deletion(-)
diff --git a/libavcodec/pngdec.c b/libavcodec/pngdec.c
index 1667530..4063347 100644
--- a/libavcodec/pngdec.c
+++ b/libavcodec/pngdec.c
@@ -892,7 +892,8 @@ static int handle_p_frame_apng(AVCodecContext *avctx,
PNGDecContext *s,
if (s->blend_op == APNG_BLEND_OP_OVER &&
avctx->pix_fmt != AV_PIX_FMT_RGBA &&
- avctx->pix_fmt != AV_PIX_FMT_GRAY8A) {
+ avctx->pix_fmt != AV_PIX_FMT_GRAY8A &&
+ avctx->pix_fmt != AV_PIX_FMT_PAL8) {
avpriv_request_sample(avctx, "Blending with pixel format %s",
av_get_pix_fmt_name(avctx->pix_fmt));
return AVERROR_PATCHWELCOME;
@@ -941,6 +942,11 @@ static int handle_p_frame_apng(AVCodecContext *avctx,
PNGDecContext *s,
foreground_alpha = foreground[1];
background_alpha = background[1];
break;
+
+ case AV_PIX_FMT_PAL8:
+ foreground_alpha = s->palette[foreground[0]] >> 24;
+ background_alpha = s->palette[background[0]] >> 24;
+ break;
}
if (foreground_alpha == 0)
@@ -951,6 +957,13 @@ static int handle_p_frame_apng(AVCodecContext *avctx,
PNGDecContext *s,
continue;
}
+ if (avctx->pix_fmt == AV_PIX_FMT_PAL8) {
+ // TODO: Alpha blending with PAL8 will likely need the
entire image converted over to RGBA first
+ avpriv_request_sample(avctx, "Alpha blending palette
samples");
+ background[0] = foreground[0];
+ continue;
+ }
+
output_alpha = foreground_alpha + FAST_DIV255((255 -
foreground_alpha) * background_alpha);
for (b = 0; b < s->bpp - 1; ++b) {
--
2.4.0
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