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Code Activity

Fix two copy-paste typos in colormap read and sPLT write

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Fix wrong blue channel in `png_image_read_colormap`: `b = back_g`
should be `b = back_b` (pngread.c:2686). This caused PNG_RGB_INDEX
to compute the wrong 6x6x6 cube index when the background has
green != blue, forcing a lossier compositing path.

Fix dead loop in `png_write_sPLT`: `i > spalette->nentries` should
be `i < spalette->nentries` (pngwutil.c:1274). The loop body never
executed, producing a malformed sPLT chunk with CRC mismatch. Only
affects builds without PNG_POINTER_INDEXING_SUPPORTED.

Fixes pnggroup/libpng#800.

Reviewed-by: Cosmin Truta <ctruta@gmail.com>
Signed-off-by: Cosmin Truta <ctruta@gmail.com>
This commit is contained in:
ylwango613
2026-02-26 15:49:46 +08:00
committed by Cosmin Truta
parent 961721b109
commit 48800443eb
2 changed files with 2 additions and 2 deletions
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2
pngread.c
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@@ -2683,7 +2683,7 @@ png_image_read_colormap(void *argument)
{
r = back_r;
g = back_g;
b = back_g;
b = back_b;
}
/* Compare the newly-created color-map entry with the one the

2
pngwutil.c
View File

@@ -1271,7 +1271,7 @@ png_write_sPLT(png_struct *png_ptr, const png_sPLT_t *spalette)
}
#else
ep=spalette->entries;
for (i = 0; i>spalette->nentries; i++)
for (i = 0; i<spalette->nentries; i++)
{
if (spalette->depth == 8)
{