From e6529ff52c05a2d3352d83a429cb69aa15f5b585 Mon Sep 17 00:00:00 2001
From: cristy <urban-warrior@git.imagemagick.org>
Date: Fri, 4 Feb 2011 20:05:32 +0000
Subject: [PATCH]

---
 ChangeLog        |  2 ++
 magick/compare.c | 53 +++++++++++++++++++-----------------------------
 2 files changed, 23 insertions(+), 32 deletions(-)

diff --git a/ChangeLog b/ChangeLog
index fbcc4482d..1ffbc69c1 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -4,6 +4,8 @@
   * Eliminate fault when reading WMF image files (reference
     http://www.imagemagick.org/discourse-server/viewtopic.php?f=2&t=17971).
   * Support multi-page transparent Postscript and PDF image files.
+  * The compare fuzz metric now returns the same correct value for
+    'xc:white xc:blue -alpha on' and 'xc:white xc:blue -alpha on'.
 
 2011-01-29  6.6.7-4 Paul Heckbert  <ph@cs.cm...>
   * Move coders/tiff.c conditional compile to define TIFF exception /
diff --git a/magick/compare.c b/magick/compare.c
index f54875480..f593d34e1 100644
--- a/magick/compare.c
+++ b/magick/compare.c
@@ -510,8 +510,8 @@ static MagickBooleanType GetFuzzDistortion(const Image *image,
     if (status == MagickFalse)
       continue;
     p=GetCacheViewVirtualPixels(image_view,0,y,image->columns,1,exception);
-    q=GetCacheViewVirtualPixels(reconstruct_view,0,y,
-      reconstruct_image->columns,1,exception);
+    q=GetCacheViewVirtualPixels(reconstruct_view,0,y,reconstruct_image->columns,
+      1,exception);
     if ((p == (const PixelPacket *) NULL) || (q == (const PixelPacket *) NULL))
       {
         status=MagickFalse;
@@ -523,50 +523,34 @@ static MagickBooleanType GetFuzzDistortion(const Image *image,
     for (x=0; x < (ssize_t) image->columns; x++)
     {
       MagickRealType
-        distance,
-        scale;
+        distance;
 
-      scale=1.0;
-      if ((channel & OpacityChannel) != 0)
-        {
-          if (image->matte != MagickFalse)
-            scale*=QuantumScale*GetAlphaPixelComponent(p);
-          if (reconstruct_image->matte != MagickFalse)
-            scale*=QuantumScale*GetAlphaPixelComponent(q);
-        }
-      if (((channel & IndexChannel) != 0) &&
-          (image->colorspace == CMYKColorspace) &&
-          (reconstruct_image->colorspace == CMYKColorspace))
-        {
-          scale*=(MagickRealType) (QuantumScale*(QuantumRange-indexes[x]));
-          scale*=(MagickRealType) (QuantumScale*(QuantumRange-
-            reconstruct_indexes[x]));
-        }
       if ((channel & RedChannel) != 0)
         {
           distance=QuantumScale*(p->red-(MagickRealType) q->red);
-          channel_distortion[RedChannel]+=scale*distance*distance;
-          channel_distortion[AllChannels]+=scale*distance*distance;
+          channel_distortion[RedChannel]+=distance*distance;
+          channel_distortion[AllChannels]+=distance*distance;
         }
       if ((channel & GreenChannel) != 0)
         {
           distance=QuantumScale*(p->green-(MagickRealType) q->green);
-          channel_distortion[GreenChannel]+=scale*distance*distance;
-          channel_distortion[AllChannels]+=scale*distance*distance;
+          channel_distortion[GreenChannel]+=distance*distance;
+          channel_distortion[AllChannels]+=distance*distance;
         }
       if ((channel & BlueChannel) != 0)
         {
           distance=QuantumScale*(p->blue-(MagickRealType) q->blue);
-          channel_distortion[BlueChannel]+=scale*distance*distance;
-          channel_distortion[AllChannels]+=scale*distance*distance;
+          channel_distortion[BlueChannel]+=distance*distance;
+          channel_distortion[AllChannels]+=distance*distance;
         }
-      if (((channel & OpacityChannel) != 0) && ((image->matte != MagickFalse) ||          (reconstruct_image->matte != MagickFalse)))
+      if (((channel & OpacityChannel) != 0) && ((image->matte != MagickFalse) ||
+          (reconstruct_image->matte != MagickFalse)))
         {
           distance=QuantumScale*((image->matte != MagickFalse ? p->opacity :
             OpaqueOpacity)-(reconstruct_image->matte != MagickFalse ?
             q->opacity : OpaqueOpacity));
-          channel_distortion[OpacityChannel]+=QuantumScale*distance*distance;
-          channel_distortion[AllChannels]+=QuantumScale*distance*distance;
+          channel_distortion[OpacityChannel]+=distance*distance;
+          channel_distortion[AllChannels]+=distance*distance;
         }
       if (((channel & IndexChannel) != 0) &&
           (image->colorspace == CMYKColorspace) &&
@@ -574,8 +558,8 @@ static MagickBooleanType GetFuzzDistortion(const Image *image,
         {
           distance=QuantumScale*(indexes[x]-(MagickRealType)
             reconstruct_indexes[x]);
-          channel_distortion[BlackChannel]+=scale*distance*distance;
-          channel_distortion[AllChannels]+=scale*distance*distance;
+          channel_distortion[BlackChannel]+=distance*distance;
+          channel_distortion[AllChannels]+=distance*distance;
         }
       p++;
       q++;
@@ -590,7 +574,12 @@ static MagickBooleanType GetFuzzDistortion(const Image *image,
   image_view=DestroyCacheView(image_view);
   for (i=0; i <= (ssize_t) AllChannels; i++)
     distortion[i]/=((double) image->columns*image->rows);
-  distortion[AllChannels]/=(double) GetNumberChannels(image,channel);
+  if (((channel & OpacityChannel) != 0) && ((image->matte != MagickFalse) ||
+      (reconstruct_image->matte != MagickFalse)))
+    distortion[AllChannels]/=(double) (GetNumberChannels(image,channel)-1);
+  else
+    distortion[AllChannels]/=(double) GetNumberChannels(image,channel);
+  distortion[AllChannels]=sqrt(distortion[AllChannels]);
   return(status);
 }
 
-- 
2.40.0