From: Niklas Haas <g...@haasn.dev> OpenEXR always uses premultiplied alpha, as per the spec.
cf. https://openexr.com/en/latest/TechnicalIntroduction.html > By convention, all color channels are premultiplied by alpha, so that > `foreground + (1-alpha) x background` performs a correct “over” operation. > (See Premultiplied vs. Un-Premultiplied Color Channels) > > In the visual effects industry premultiplied color channels are the norm, > and application software packages typically use internal image > representations that are also premultiplied. --- libavcodec/exr.c | 3 +++ libavcodec/exrenc.c | 3 +++ 2 files changed, 6 insertions(+) diff --git a/libavcodec/exr.c b/libavcodec/exr.c index 0a6aab662e..9f0daf863c 100644 --- a/libavcodec/exr.c +++ b/libavcodec/exr.c @@ -2124,6 +2124,9 @@ static int decode_frame(AVCodecContext *avctx, AVFrame *picture, return AVERROR_INVALIDDATA; } + if (s->channel_offsets[3] >= 0) + avctx->alpha_mode = AVALPHA_MODE_PREMULTIPLIED; + #if FF_API_EXR_GAMMA if (s->apply_trc_type != AVCOL_TRC_UNSPECIFIED) avctx->color_trc = s->apply_trc_type; diff --git a/libavcodec/exrenc.c b/libavcodec/exrenc.c index c9685890ea..54f63d9eb6 100644 --- a/libavcodec/exrenc.c +++ b/libavcodec/exrenc.c @@ -553,4 +553,7 @@ const FFCodec ff_exr_encoder = { FF_CODEC_ENCODE_CB(encode_frame), .close = encode_close, CODEC_PIXFMTS(AV_PIX_FMT_GRAYF32, AV_PIX_FMT_GBRPF32, AV_PIX_FMT_GBRAPF32), + .alpha_modes = (const enum AVAlphaMode[]) { + AVALPHA_MODE_PREMULTIPLIED, AVALPHA_MODE_UNSPECIFIED + }, }; -- 2.50.1 _______________________________________________ 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".
