On Fri, 12 Jul 2024, Leo Izen wrote:

Indexed color images use three colors for sBIT, but the function
ff_png_get_nb_channels returns 1 in this case. We should avoid erroring
out on valid files in this scenario.

Please mention that this is a regression since 84b454935fae2633a8a5dd075e22393f3e8f932f.


Signed-off-by: Leo Izen <leo.i...@gmail.com>
Reported-by: Ramiro Polla <ramiro.po...@gmail.com>
---
libavcodec/pngdec.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/libavcodec/pngdec.c b/libavcodec/pngdec.c
index 180806e5e1..b0d02c97dd 100644
--- a/libavcodec/pngdec.c
+++ b/libavcodec/pngdec.c
@@ -1084,7 +1084,7 @@ static int decode_sbit_chunk(AVCodecContext *avctx, 
PNGDecContext *s,
        return AVERROR_INVALIDDATA;
    }

-    channels = ff_png_get_nb_channels(s->color_type);
+    channels = s->color_type & PNG_COLOR_MASK_PALETTE ? 3 : 
ff_png_get_nb_channels(s->color_type);


LGTM, also please backport this to the affected branches!

Thanks,
Marton


    if (bytestream2_get_bytes_left(gb) != channels)
        return AVERROR_INVALIDDATA;
--
2.45.2

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