[FFmpeg-cvslog] lavc/pngenc: Support writing colorspace tags.
Niklas Haas
git at videolan.org
Sat Feb 28 03:46:13 CET 2015
ffmpeg | branch: master | Niklas Haas <git at nand.wakku.to> | Fri Feb 27 21:31:38 2015 +0100| [888a33c070f1e96b683e13e7b0b6af891428c6c3] | committer: Michael Niedermayer
lavc/pngenc: Support writing colorspace tags.
These are defined in http://www.w3.org/TR/PNG/#11addnlcolinfo.
> http://git.videolan.org/gitweb.cgi/ffmpeg.git/?a=commit;h=888a33c070f1e96b683e13e7b0b6af891428c6c3
---
libavcodec/pngenc.c | 87 +++++++++++++++++++++++++++++++++++++++++++++++++++
1 file changed, 87 insertions(+)
diff --git a/libavcodec/pngenc.c b/libavcodec/pngenc.c
index ef33332..9fd8eef 100644
--- a/libavcodec/pngenc.c
+++ b/libavcodec/pngenc.c
@@ -231,6 +231,81 @@ static int png_write_row(PNGEncContext *s, const uint8_t *data, int size)
return 0;
}
+#define AV_WB32_PNG(buf, n) (AV_WB32(buf, round((n) * 100000)))
+static int png_get_chrm(enum AVColorPrimaries prim, uint8_t *buf)
+{
+ double rx, ry, gx, gy, bx, by, wx = 0.3127, wy = 0.3290;
+ switch (prim) {
+ case AVCOL_PRI_BT709:
+ rx = 0.640; ry = 0.330;
+ gx = 0.300; gy = 0.600;
+ bx = 0.150; by = 0.060;
+ break;
+ case AVCOL_PRI_BT470M:
+ rx = 0.670; ry = 0.330;
+ gx = 0.210; gy = 0.710;
+ bx = 0.140; by = 0.080;
+ wx = 0.310; wy = 0.316;
+ break;
+ case AVCOL_PRI_BT470BG:
+ rx = 0.640; ry = 0.330;
+ gx = 0.290; gy = 0.600;
+ bx = 0.150; by = 0.060;
+ break;
+ case AVCOL_PRI_SMPTE170M:
+ case AVCOL_PRI_SMPTE240M:
+ rx = 0.630; ry = 0.340;
+ gx = 0.310; gy = 0.595;
+ bx = 0.155; by = 0.070;
+ break;
+ case AVCOL_PRI_BT2020:
+ rx = 0.708; ry = 0.292;
+ gx = 0.170; gy = 0.797;
+ bx = 0.131; by = 0.046;
+ break;
+ default:
+ return 0;
+ }
+
+ AV_WB32_PNG(buf , wx); AV_WB32_PNG(buf + 4 , wy);
+ AV_WB32_PNG(buf + 8 , rx); AV_WB32_PNG(buf + 12, ry);
+ AV_WB32_PNG(buf + 16, gx); AV_WB32_PNG(buf + 20, gy);
+ AV_WB32_PNG(buf + 24, bx); AV_WB32_PNG(buf + 28, by);
+ return 1;
+}
+
+static int png_get_gama(enum AVColorTransferCharacteristic trc, uint8_t *buf)
+{
+ double gamma;
+ switch (trc) {
+ case AVCOL_TRC_BT709:
+ case AVCOL_TRC_SMPTE170M:
+ case AVCOL_TRC_SMPTE240M:
+ case AVCOL_TRC_BT1361_ECG:
+ case AVCOL_TRC_BT2020_10:
+ case AVCOL_TRC_BT2020_12:
+ /* these share a segmented TRC, but gamma 1.961 is a close
+ approximation, and also more correct for decoding content */
+ gamma = 1.961;
+ break;
+ case AVCOL_TRC_GAMMA22:
+ case AVCOL_TRC_IEC61966_2_1:
+ gamma = 2.2;
+ break;
+ case AVCOL_TRC_GAMMA28:
+ gamma = 2.8;
+ break;
+ case AVCOL_TRC_LINEAR:
+ gamma = 1.0;
+ break;
+ default:
+ return 0;
+ }
+
+ AV_WB32_PNG(buf, 1.0 / gamma);
+ return 1;
+}
+
static int encode_frame(AVCodecContext *avctx, AVPacket *pkt,
const AVFrame *pict, int *got_packet)
{
@@ -358,6 +433,18 @@ static int encode_frame(AVCodecContext *avctx, AVPacket *pkt,
}
png_write_chunk(&s->bytestream, MKTAG('p', 'H', 'Y', 's'), s->buf, 9);
+ /* write colorspace information */
+ if (pict->color_primaries == AVCOL_PRI_BT709 &&
+ pict->color_trc == AVCOL_TRC_IEC61966_2_1) {
+ s->buf[0] = 1; /* rendering intent, relative colorimetric by default */
+ png_write_chunk(&s->bytestream, MKTAG('s', 'R', 'G', 'B'), s->buf, 1);
+ }
+
+ if (png_get_chrm(pict->color_primaries, s->buf))
+ png_write_chunk(&s->bytestream, MKTAG('c', 'H', 'R', 'M'), s->buf, 32);
+ if (png_get_gama(pict->color_trc, s->buf))
+ png_write_chunk(&s->bytestream, MKTAG('g', 'A', 'M', 'A'), s->buf, 4);
+
/* put the palette if needed */
if (color_type == PNG_COLOR_TYPE_PALETTE) {
int has_alpha, alpha, i;
More information about the ffmpeg-cvslog
mailing list