From: Niklas Haas <g...@haasn.dev>
JPEG XL supports both premultiplied and straight alpha, and the basic info
struct contains signalling for this. Forward the correct tagging on decode
and encode.
---
libavcodec/libjxldec.c | 6 ++++++
libavcodec/libjxlenc.c | 15 +++++++++++++++
2 files changed, 21 insertions(+)
diff --git a/libavcodec/libjxldec.c b/libavcodec/libjxldec.c
index 96c338d1b4..0c4091850c 100644
--- a/libavcodec/libjxldec.c
+++ b/libavcodec/libjxldec.c
@@ -433,6 +433,12 @@ static int libjxl_receive_frame(AVCodecContext *avctx,
AVFrame *frame)
if (ctx->basic_info.have_animation)
ctx->anim_timebase =
av_make_q(ctx->basic_info.animation.tps_denominator,
ctx->basic_info.animation.tps_numerator);
+ if (ctx->basic_info.alpha_bits) {
+ if (ctx->basic_info.alpha_premultiplied)
+ avctx->alpha_mode = AVALPHA_MODE_PREMULTIPLIED;
+ else
+ avctx->alpha_mode = AVALPHA_MODE_STRAIGHT;
+ }
continue;
case JXL_DEC_COLOR_ENCODING:
av_log(avctx, AV_LOG_DEBUG, "COLOR_ENCODING event emitted\n");
diff --git a/libavcodec/libjxlenc.c b/libavcodec/libjxlenc.c
index 823abcafb8..924a835436 100644
--- a/libavcodec/libjxlenc.c
+++ b/libavcodec/libjxlenc.c
@@ -351,6 +351,15 @@ static int libjxl_preprocess_stream(AVCodecContext *avctx,
const AVFrame *frame,
jxl_fmt->data_type = info.bits_per_sample <= 8 ? JXL_TYPE_UINT8 :
JXL_TYPE_UINT16;
}
+ if (info.alpha_bits) {
+ if (avctx->alpha_mode == AVALPHA_MODE_PREMULTIPLIED ||
+ avctx->alpha_mode == AVALPHA_MODE_UNSPECIFIED && frame->alpha_mode
== AVALPHA_MODE_PREMULTIPLIED) {
+ info.alpha_premultiplied = 1;
+ } else if (avctx->alpha_mode != AVALPHA_MODE_STRAIGHT &&
frame->alpha_mode != AVALPHA_MODE_STRAIGHT) {
+ av_log(avctx, AV_LOG_WARNING, "Unknown alpha mode, assuming
straight (independent)\n");
+ }
+ }
+
#if JPEGXL_NUMERIC_VERSION >= JPEGXL_COMPUTE_NUMERIC_VERSION(0, 8, 0)
jxl_bit_depth.bits_per_sample = bits_per_sample;
jxl_bit_depth.type = JXL_BIT_DEPTH_FROM_PIXEL_FORMAT;
@@ -713,6 +722,9 @@ const FFCodec ff_libjxl_encoder = {
FF_CODEC_CAP_AUTO_THREADS | FF_CODEC_CAP_INIT_CLEANUP |
FF_CODEC_CAP_ICC_PROFILES,
CODEC_PIXFMTS_ARRAY(libjxl_supported_pixfmts),
+ .alpha_modes = (const enum AVAlphaMode[]) {
+ AVALPHA_MODE_STRAIGHT, AVALPHA_MODE_PREMULTIPLIED,
AVALPHA_MODE_UNSPECIFIED
+ },
.p.priv_class = &libjxl_encode_class,
.p.wrapper_name = "libjxl",
};
@@ -733,6 +745,9 @@ const FFCodec ff_libjxl_anim_encoder = {
FF_CODEC_CAP_AUTO_THREADS | FF_CODEC_CAP_INIT_CLEANUP |
FF_CODEC_CAP_ICC_PROFILES,
CODEC_PIXFMTS_ARRAY(libjxl_supported_pixfmts),
+ .alpha_modes = (const enum AVAlphaMode[]) {
+ AVALPHA_MODE_STRAIGHT, AVALPHA_MODE_PREMULTIPLIED,
AVALPHA_MODE_UNSPECIFIED
+ },
.p.priv_class = &libjxl_encode_class,
.p.wrapper_name = "libjxl",
};
--
2.50.1
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