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lavc/pngenc: Support writing colorspace tags.

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These are defined in http://www.w3.org/TR/PNG/#11addnlcolinfo.
This commit is contained in:
Niklas Haas 2015-02-27 21:31:38 +01:00 committed by Michael Niedermayer
parent 0a23129bfc
commit 888a33c070
1 changed files with 87 additions and 0 deletions
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87
libavcodec/pngenc.c
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@ -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;