https://github.com/ImageMagick/ImageMagick/issues/1298

diff --git a/MagickCore/composite.c b/MagickCore/composite.c
index 1dd6bb8de4900c3d0671281b7b3a4c4bb7a8c8f4..8fa83ca4ca2aa53116d52b4cfb936f8b75f8697d 100644 (file)
--- a/MagickCore/composite.c
+++ b/MagickCore/composite.c
@@ -1613,6 +1613,11 @@ MagickExport MagickBooleanType CompositeImage(Image *image,
                   Da*GetPixelIntensity(image,q) ? Sa : Da;
                 break;
               }
+              case DifferenceCompositeOp:
+              {
+                pixel=QuantumRange*fabs(Sa-Da);
+                break;
+              }
               case LightenIntensityCompositeOp:
               {
                 pixel=Sa*GetPixelIntensity(source_image,p) >

diff --git a/MagickCore/morphology.c b/MagickCore/morphology.c
index 131396836d0dc272dd9ed4f0e7684554484b8414..258432562a496e616c53eba7e7d17f5be96345e3 100644 (file)
--- a/MagickCore/morphology.c
+++ b/MagickCore/morphology.c
@@ -3984,7 +3984,7 @@ MagickPrivate Image *MorphologyApply(const Image *image,
             (void) FormatLocaleFile(stderr,
               "\n%s: Difference of Dilate and Erode",CommandOptionToMnemonic(
               MagickMorphologyOptions, method) );
-          (void) CompositeImage(curr_image,save_image,OutCompositeOp,
+          (void) CompositeImage(curr_image,save_image,DifferenceCompositeOp,
             MagickTrue,0,0,exception);
           save_image = DestroyImage(save_image); /* finished with save image */
           break;