No changes, just refactor common code in wxImage cloning functions.

Extract code common to several wxImage methods creating new images based on an
existing one in a new MakeEmptyClone() method.

Closes #12682.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@66167 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

include/wx/image.h

@@ -591,6 +591,24 @@ protected:
 private:
     friend class WXDLLIMPEXP_FWD_CORE wxImageHandler;
 
+    // Possible values for MakeEmptyClone() flags.
+    enum
+    {
+        // Create an image with the same orientation as this one. This is the
+        // default and only exists for symmetry with SwapOrientation.
+        Clone_SameOrientation = 0,
+
+        // Create an image with the same height as this image width and the
+        // same width as this image height.
+        Clone_SwapOrientation = 1
+    };
+
+    // Returns a new blank image with the same dimensions (or with width and
+    // height swapped if Clone_SwapOrientation flag is given), alpha, and mask
+    // as this image itself. This is used by several functions creating
+    // modified versions of this image.
+    wxImage MakeEmptyClone(int flags = Clone_SameOrientation) const;
+
 #if wxUSE_STREAMS
     // read the image from the specified stream updating image type if
     // successful