pngenc: write sample aspect ratio

Signed-off-by: Paul B Mahol <onemda@gmail.com>

libavcodec/pngenc.c

@@ -335,6 +335,11 @@ static int encode_frame(AVCodecContext *avctx, AVPacket *pkt,
 
     png_write_chunk(&s->bytestream, MKTAG('I', 'H', 'D', 'R'), s->buf, 13);
 
+    AV_WB32(s->buf, avctx->sample_aspect_ratio.num);
+    AV_WB32(s->buf + 4, avctx->sample_aspect_ratio.den);
+    s->buf[8] = 0; /* unit specifier is unknown */
+    png_write_chunk(&s->bytestream, MKTAG('p', 'H', 'Y', 's'), s->buf, 9);
+
     /* put the palette if needed */
     if (color_type == PNG_COLOR_TYPE_PALETTE) {
         int has_alpha, alpha, i;

tests/ref/lavf/png

-c162094e51dc1a3203de43e496086dfd *./tests/data/images/png/02.png
+2af72da4468e61a37c220b25cb28618a *./tests/data/images/png/02.png
 ./tests/data/images/png/%02d.png CRC=0x6da01946
-248612 ./tests/data/images/png/02.png
-63805114b3723490833789277246276f *./tests/data/images/png/02.png
+248633 ./tests/data/images/png/02.png
+62b26c9582ba37dd37b76191338f3770 *./tests/data/images/png/02.png
 ./tests/data/images/png/%02d.png CRC=0x831a2963
-41666 ./tests/data/images/png/02.png
-b4c1f0b706a296ba6e791d436757dc5f *./tests/data/images/png/02.png
+41687 ./tests/data/images/png/02.png
+b4e38244c97debe3f528e7d1adb283ef *./tests/data/images/png/02.png
 ./tests/data/images/png/%02d.png CRC=0x5984c023
-511879 ./tests/data/images/png/02.png
+511900 ./tests/data/images/png/02.png