negate correlation image for NCC metric

ImageMagick · Feb 15, 2025 · 61c6651 · 61c6651
1 parent c6272cc
commit 61c6651
Showing 1 changed file with 5 additions and 1 deletion.
diff --git a/magick/compare.c b/magick/compare.c
@@ -2209,7 +2209,11 @@ MagickExport Image *SimilarityMetricImage(Image *image,const Image *reference,
         }
       if (metric == PerceptualHashErrorMetric)
         similarity=MagickMin(0.01*similarity,1.0);
-      SetPixelRed(q,(double) QuantumRange*similarity);
+      if (metric == NormalizedCrossCorrelationErrorMetric)
+        SetPixelRed(q,ClampToQuantum((double) QuantumRange-QuantumRange*
+          similarity));
+      else
+        SetPixelRed(q,ClampToQuantum((double) QuantumRange*similarity));
       SetPixelGreen(q,GetPixelRed(q));
       SetPixelBlue(q,GetPixelRed(q));
       q++;