https://imagemagick.org/discourse-server/viewtopic.php?f=1&t=35970

diff --git a/MagickCore/signature.c b/MagickCore/signature.c
index 10223eab5c01f1e7ebb6960c1da16cf6ee81310b..e17b92c1fb6695cd48bc1b297495931b20149945 100644 (file)
--- a/MagickCore/signature.c
+++ b/MagickCore/signature.c
@@ -476,7 +476,7 @@ MagickExport MagickBooleanType SignatureImage(Image *image,
   char
     *hex_signature;
 
-  double
+  float
     pixel;
 
   register const Quantum
@@ -537,9 +537,10 @@ MagickExport MagickBooleanType SignatureImage(Image *image,
 
         PixelChannel channel = GetPixelChannelChannel(image,i);
         PixelTrait traits = GetPixelChannelTraits(image,channel);
-        if (traits == UndefinedPixelTrait)
+        if ((traits == UndefinedPixelTrait) ||
+            ((traits & UpdatePixelTrait) == 0))
           continue;
-        pixel=QuantumScale*p[i];
+        pixel=(float) (QuantumScale*p[i]);
         if (signature_info->lsb_first == MagickFalse)
           for (j=(ssize_t) sizeof(pixel)-1; j >= 0; j--)
             *q++=(unsigned char) ((unsigned char *) &pixel)[j];