File ImageMagick-CVE-2020-27762.patch of Package ImageMagick.23974

diff --git a/coders/hdr.c b/coders/hdr.c
index ab02f8e52..77e3c6336 100644
--- a/coders/hdr.c
+++ b/coders/hdr.c
@@ -786,9 +786,12 @@ static MagickBooleanType WriteHDRImage(const ImageInfo *image_info,Image *image)
             exponent;
 
           gamma=frexp(gamma,&exponent)*256.0/gamma;
-          pixel[0]=(unsigned char) (gamma*QuantumScale*GetPixelRed(p));
-          pixel[1]=(unsigned char) (gamma*QuantumScale*GetPixelGreen(p));
-          pixel[2]=(unsigned char) (gamma*QuantumScale*GetPixelBlue(p));
+          if (GetPixelRed(p) > 0)
+            pixel[0]=(unsigned char) (gamma*QuantumScale*GetPixelRed(p));
+          if (GetPixelGreen(p) > 0)
+            pixel[1]=(unsigned char) (gamma*QuantumScale*GetPixelGreen(p));
+          if (GetPixelBlue(p) > 0)
+            pixel[2]=(unsigned char) (gamma*QuantumScale*GetPixelBlue(p));
           pixel[3]=(unsigned char) (exponent+128);
         }
       if ((image->columns >= 8) && (image->columns <= 0x7ffff))