Sigma Fix for Cylindrical Gaussian Filters (including Mapped Blurs)

diff --git a/ChangeLog b/ChangeLog
index aab443b4b21cd885684c71bcfed2ea3700109b0e..230b41ae532417dd80f5e4ed81b666cad79e7ab3 100644 (file)
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,11 @@
+2010-10-02  6.6.4-9 Anthony Thyssen <A.Thyssen@griffith...>
+  * Added sqrt(2) bluring default for Gaussian Filter if used as a
+    Cylindrical EWA filter.  This resulted in the last aliasing issue
+    that was present in tests for Gaussian EWA resampling.
+    However it is still a very blury filter for default use in EWA.
+  * Adjusted Variable Mapping Blur Composition so user arguments actual
+    relate properly to the sigma of the blur for a maximum mapping value.
+
 2010-09-28  6.6.4-8 Nicolas Robidoux <nicolas.robidoux@gmail...>
   * Chantal Racette double checked the bounding parallelogram computation
     in resample.c (and I tightened the comments).

diff --git a/magick/composite.c b/magick/composite.c
index c04c863215cced7a71354366ee092034af66e728..db6f048ad10004974efd831684b09427e3bec3bc 100644 (file)
--- a/magick/composite.c
+++ b/magick/composite.c
@@ -1761,7 +1761,7 @@ MagickExport MagickBooleanType CompositeImageChannel(Image *image,
       pixel=zero;
       exception=(&image->exception);
       resample_filter=AcquireResampleFilter(image,&image->exception);
-      SetResampleFilter(resample_filter,GaussianFilter,1.0);
+      SetResampleFilter(resample_filter,GaussianFilter,2.0);
       destination_view=AcquireCacheView(destination_image);
       composite_view=AcquireCacheView(composite_image);
       for (y=0; y < (ssize_t) composite_image->rows; y++)

diff --git a/magick/resample.c b/magick/resample.c
index fc245dc4cbe268cf9061037862362f5153fb063d..eaa9fcefcdfecd422d7f0b19a8724f0c61040bcd 100644 (file)
--- a/magick/resample.c
+++ b/magick/resample.c
@@ -1779,10 +1779,11 @@ MagickExport void SetResampleFilter(ResampleFilter *resample_filter,
       resample_filter->filter = PointFilter;
     }
 
+  /* Get the practical working support for the filter,
+   * after any API call blur factors have been accoded for.
+   */
 #if EWA
   resample_filter->support = GetResizeFilterSupport(resize_filter);
-  if ( resample_filter->filter == GaussianFilter )
-    resample_filter->support = 2.0;  /* larger gaussian support */
 #else
   resample_filter->support = 2.0;  /* fixed support size for HQ-EWA */
 #endif

diff --git a/magick/resize.c b/magick/resize.c
index 0ace0c3f8c1bec090b00413c2331b124a25ac720..4f64ceb27bc46c50015431ed85c4294133b0131a 100644 (file)
--- a/magick/resize.c
+++ b/magick/resize.c
@@ -762,47 +762,25 @@ MagickExport ResizeFilter *AcquireResizeFilter(const Image *image,
   */
   filter_type=mapping[filter].filter;
   window_type=mapping[filter].window;
-  /*
-    Filter blur -- scaling both filter and support window.
-  */
-  resize_filter->blur=blur;
-  artifact=GetImageArtifact(image,"filter:blur");
-  if (artifact != (const char *) NULL)
-    resize_filter->blur=StringToDouble(artifact);
-  if (resize_filter->blur < MagickEpsilon)
-    resize_filter->blur=(MagickRealType) MagickEpsilon;
-  /*
-    Cylindrical Filters should use Bessel instead of Sinc, unless a
-    Sinc filter was specifically requested.
-    Result may be overridden by expert settings later.
-  */
+  /* Cylindrical Filters should use Bessel instead of Sinc */
   if (cylindrical != MagickFalse)
     switch (filter_type)
     {
       case SincFilter:
-      {
-        /*
-          Promote 1D Sinc Filter to a 2D Bessel filter, as long as the
-          user did not directly request a 'Sinc' filter.
-        */
+        /* Promote 1D Sinc Filter to a 2D Bessel filter. */
         if ( filter != SincFilter )
           filter_type=BesselFilter;
         break;
-      }
       case SincFastFilter:
-      {
         /* Ditto for SincFast variant */
         if ( filter != SincFastFilter )
           filter_type=BesselFilter;
         break;
-      }
       case LanczosFilter:
-      {
-        /* Promote Lanczos (Sinc-Sinc) to Lanczos (Bessel-Bessel). */
+        /* Promote Lanczos from a Sinc-Sinc to a Bessel-Bessel */
         filter_type=BesselFilter;
         window_type=BesselFilter;
         break;
-      }
       default:
         /*
           What about other filters to make them 'cylindrical
@@ -866,6 +844,31 @@ MagickExport ResizeFilter *AcquireResizeFilter(const Image *image,
   resize_filter->window=filters[window_type].function;
   resize_filter->scale=filters[window_type].scale;
   resize_filter->signature=MagickSignature;
+  /* Filter blur -- scaling both filter and support window.  */
+  resize_filter->blur=blur;
+  artifact=GetImageArtifact(image,"filter:blur");
+  if (artifact != (const char *) NULL)
+    resize_filter->blur=StringToDouble(artifact);
+  if (resize_filter->blur < MagickEpsilon)
+    resize_filter->blur=(MagickRealType) MagickEpsilon;
+
+  if (cylindrical != MagickFalse)
+    switch (filter_type)
+    {
+      case PointFilter:
+      case BoxFilter:
+        /* Support for Cylindrical Box should be sqrt(2)/2 */
+        resize_filter->support=MagickSQ1_2;
+        break;
+      case GaussianFilter:
+        /* Cylindrical Gaussian should have a sigma of sqrt(2)/2
+         * and not the default sigma of 1/2 - so use blur to enlarge
+         * and adjust support so actual practical support = 2.0 by default
+         */
+        resize_filter->blur *= MagickSQ2;
+        resize_filter->support = MagickSQ2; /* which times blur => 2.0 */
+        break;
+    }
   /* Filter support overrides. */
   artifact=GetImageArtifact(image,"filter:lobes");
   if (artifact != (const char *) NULL)