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Code Issues Releases Activity

avcodec/pngenc: fix sBIT writing for indexed-color PNGs

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We currently write invalid sBIT entries for indexed PNGs, which by PNG
specification[1] must be 3-bytes long. The values also are capped at 8
for indexed-color PNGs, not the palette depth. This patch fixes both of
these issues previously fixed in the decoder, but not the encoder.

[1]: https://www.w3.org/TR/png-3/#11sBIT

Regression since: c125860892.

Signed-off-by: Leo Izen <leo.izen@gmail.com>
Reported-by: Ramiro Polla: <ramiro.polla@gmail.com>
This commit is contained in:
Leo Izen 2024-07-19 12:04:20 -04:00
parent 825606641b
commit 7bb5626fa7
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GPG Key ID: 764E48EA48221833
1 changed files with 3 additions and 2 deletions
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5
libavcodec/pngenc.c
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@ -469,8 +469,9 @@ static int encode_headers(AVCodecContext *avctx, const AVFrame *pict)
if (png_get_gama(pict->color_trc, s->buf))
png_write_chunk(&s->bytestream, MKTAG('g', 'A', 'M', 'A'), s->buf, 4);
if (avctx->bits_per_raw_sample > 0 && avctx->bits_per_raw_sample < s->bit_depth) {
int len = ff_png_get_nb_channels(s->color_type);
if (avctx->bits_per_raw_sample > 0 &&
avctx->bits_per_raw_sample < (s->color_type & PNG_COLOR_MASK_PALETTE ? 8 : s->bit_depth)) {
int len = s->color_type & PNG_COLOR_MASK_PALETTE ? 3 : ff_png_get_nb_channels(s->color_type);
memset(s->buf, avctx->bits_per_raw_sample, len);
png_write_chunk(&s->bytestream, MKTAG('s', 'B', 'I', 'T'), s->buf, len);
}