https://www.imagemagick.org/discourse-server/viewtopic.php?f=3&t=32407

diff --git a/coders/gif.c b/coders/gif.c
index ab2d76e8d38fdc458059eefcedb1b6115525f7ea..6202f5e1663f1ac2fef15e2a1dbf2918b8b333d8 100644 (file)
--- a/coders/gif.c
+++ b/coders/gif.c
@@ -1255,7 +1255,7 @@ static Image *ReadGIFImage(const ImageInfo *image_info,ExceptionInfo *exception)
     image->colors=BitSet((int) flag,0x80) == 0 ? global_colors : one <<
       ((size_t) (flag & 0x07)+1);
     if (opacity >= (ssize_t) image->colors)
-      opacity=(-1);
+      image->colors=opacity+1;
     image->page.width=page.width;
     image->page.height=page.height;
     image->page.y=page.y;