Added alpha saving support to TIFF image handler.

Added support for saving alpha with RGB, greyscale, and black and white images.


git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@68948 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

tests/testimage.h

@@ -31,9 +31,10 @@ struct assertion_traits<wxImage>
 
     static std::string toString(const wxImage& image)
     {
-        return wxString::Format("image of size %d*%d",
+        return wxString::Format("image of size %d*%d with%s alpha",
                                 image.GetWidth(),
-                                image.GetHeight())
+                                image.GetHeight(),
+                                image.HasAlpha() ? "" : "out")
                 .ToStdString();
     }
 };