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avcodec/apng: Add partial support for blending with PAL8 pixel format

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Currently restricted to blending pixels that only contain either
0 or 255 in their alpha components

Signed-off-by: Donny Yang <work@kota.moe>
Reviewed-by: Paul B Mahol <onemda@gmail.com>
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>
This commit is contained in:
Donny Yang
2015-06-02 15:49:27 +00:00
committed by Michael Niedermayer
parent 33292c07fe
commit 130a6c04a4
1 changed files with 14 additions and 1 deletions
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15
libavcodec/pngdec.c
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@@ -897,7 +897,8 @@ 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;
@@ -948,6 +949,11 @@ 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)
@@ -958,6 +964,13 @@ 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) {