File ImageMagick-convert-tiff-resize-png.patch of Package ImageMagick.19146
diff --git a/coders/png.c b/coders/png.c
index c80b4bcdcd..6754a6b9b5 100644
--- a/coders/png.c
+++ b/coders/png.c
@@ -8757,6 +8757,7 @@ static MagickBooleanType WriteOnePNGImage(MngInfo *mng_info,
Sometimes we get PseudoClass images whose RGB values don't match
the colors in the colormap. This code syncs the RGB values.
*/
+ image->depth=GetImageQuantumDepth(image,MagickFalse);
if (image->depth <= 8 && image->taint && image->storage_class == PseudoClass)
(void) SyncImage(image,exception);