+#elif defined(__WXCOCOA__)
+ // Cocoa is standard RGB or RGBA (normally it is RGBA)
+ typedef wxPixelFormat<unsigned char, 24, 0, 1, 2> wxNativePixelFormat;
+
+ #define wxPIXEL_FORMAT_ALPHA 3
+#elif defined(__WXGTK__)
+ // Under GTK+ 2.X we use GdkPixbuf, which should be RGBA
+ typedef wxPixelFormat<unsigned char, 32, 0, 1, 2> wxNativePixelFormat;
+
+ #define wxPIXEL_FORMAT_ALPHA 3