Changed behaviour of wxImageResizeQuality parameter in wxImage.Scale and wxImage...

Made the following changes:

* Formerly specifying to resize using wxIMAGE_QUALITY_BICUBIC or wxIMAGE_QUALITY_BILINEAR could result in the ResampleBox method being used. Now always resize with the method that the user actually specified.

* Added wxIMAGE_QUALITY_BOX_AVERAGE to explicitly allow resizing with the ResampleBox method.

* Previously wxIMAGE_QUALITY_HIGH was equal to wxIMAGE_QUALITY_BICUBIC. It has been changed to use wxIMAGE_QUALITY_BOX_AVERAGE when reducing the size of an image and wxIMAGE_QUALITY_BICUBIC in all other cases.

Closes #12845.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@67203 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

diff --git a/include/wx/image.h b/include/wx/image.h
index 43e7115ea03bde494c2bd5fd4c0dcc11c2ab47bf..e9fb5c54694005d4fb7621610723e28bf0ff4f08 100644 (file)
--- a/include/wx/image.h
+++ b/include/wx/image.h
@@ -62,12 +62,13 @@ enum wxImageResizeQuality
     wxIMAGE_QUALITY_NEAREST = 0,
     wxIMAGE_QUALITY_BILINEAR = 1,
     wxIMAGE_QUALITY_BICUBIC = 2,
+    wxIMAGE_QUALITY_BOX_AVERAGE = 3,
 
     // default quality is low (but fast)
     wxIMAGE_QUALITY_NORMAL = wxIMAGE_QUALITY_NEAREST,
 
     // highest (but best) quality
-    wxIMAGE_QUALITY_HIGH = wxIMAGE_QUALITY_BICUBIC
+    wxIMAGE_QUALITY_HIGH
 };
 
 // alpha channel values: fully transparent, default threshold separating

diff --git a/interface/wx/image.h b/interface/wx/image.h
index 105ee05f0ff4dd0f7b328c23c07c2e666e550c17..fc75c139c7a1bd58ec13f321adf2de0b1573b701 100644 (file)
--- a/interface/wx/image.h
+++ b/interface/wx/image.h
@@ -39,10 +39,24 @@ enum wxImageResizeQuality
     /// Highest quality but slowest execution time.
     wxIMAGE_QUALITY_BICUBIC,
 
-    /// Default image resizing algorithm used by wxImage::Scale().
+    /**
+    Use surrounding pixels to calculate an average that will be used for
+    new pixels. This method is typically used when reducing the size of
+    an image.
+    wxIMAGE_QUALITY_BOX_AVERAGE,
+
+    /**
+    Default image resizing algorithm used by wxImage::Scale(). Currently
+    the same as wxIMAGE_QUALITY_NEAREST.
+    */
     wxIMAGE_QUALITY_NORMAL,
 
-    /// Best image resizing algorithm, currently same as wxIMAGE_QUALITY_BICUBIC.
+    /**
+    Best image resizing algorithm. Since version 2.9.2 this results in
+    wxIMAGE_QUALITY_BOX_AVERAGE being used when reducing the size of the
+    image (meaning that both the new width and height will be smaller than
+    the original size). Otherwise wxIMAGE_QUALITY_BICUBIC is used.
+    */
     wxIMAGE_QUALITY_HIGH
 };
 

diff --git a/src/common/image.cpp b/src/common/image.cpp
index a055858d4d21fcc0796aaed7e7195fbd9f9cb2d4..1d82b39ca581000c1c07db1a04afbb731b1767de 100644 (file)
--- a/src/common/image.cpp
+++ b/src/common/image.cpp
@@ -442,23 +442,16 @@ wxImage::Scale( int width, int height, wxImageResizeQuality quality ) const
     if ( old_width == width && old_height == height )
         return *this;
 
-    // resample the image using either the nearest neighbourhood, bilinear or
-    // bicubic method as specified
-    switch ( quality )
+    if (quality == wxIMAGE_QUALITY_HIGH)
     {
-        case wxIMAGE_QUALITY_BICUBIC:
-        case wxIMAGE_QUALITY_BILINEAR:
-            // both of these algorithms should be used for up-sampling the
-            // image only, when down-sampling always use box averaging for best
-            // results
-            if ( width < old_width && height < old_height )
-                image = ResampleBox(width, height);
-            else if ( quality == wxIMAGE_QUALITY_BILINEAR )
-                image = ResampleBilinear(width, height);
-            else if ( quality == wxIMAGE_QUALITY_BICUBIC )
-                image = ResampleBicubic(width, height);
-            break;
+        quality = (width < old_width && height < old_height)
+            ? wxIMAGE_QUALITY_BOX_AVERAGE
+            : wxIMAGE_QUALITY_BICUBIC;
+    }
 
+    // Resample the image using the method as specified.
+    switch ( quality )
+    {
         case wxIMAGE_QUALITY_NEAREST:
             if ( old_width % width == 0 && old_width >= width &&
                 old_height % height == 0 && old_height >= height )
@@ -468,6 +461,18 @@ wxImage::Scale( int width, int height, wxImageResizeQuality quality ) const
 
             image = ResampleNearest(width, height);
             break;
+
+        case wxIMAGE_QUALITY_BILINEAR:
+            image = ResampleBilinear(width, height);
+            break;
+
+        case wxIMAGE_QUALITY_BICUBIC:
+            image = ResampleBicubic(width, height);
+            break;
+
+        case wxIMAGE_QUALITY_BOX_AVERAGE:
+            image = ResampleBox(width, height);
+            break;
     }
 
     // If the original image has a mask, apply the mask to the new image