+// alpha channel values: fully transparent, default threshold separating
+// transparent pixels from opaque for a few functions dealing with alpha and
+// fully opaque
+const unsigned char wxIMAGE_ALPHA_TRANSPARENT = 0;
+const unsigned char wxIMAGE_ALPHA_THRESHOLD = 0x80;
+const unsigned char wxIMAGE_ALPHA_OPAQUE = 0xff;
+