// automatically or using the specified colour for the mask), if it has
// any, does nothing otherwise:
bool ConvertAlphaToMask(unsigned char threshold = wxIMAGE_ALPHA_THRESHOLD);
// automatically or using the specified colour for the mask), if it has
// any, does nothing otherwise:
bool ConvertAlphaToMask(unsigned char threshold = wxIMAGE_ALPHA_THRESHOLD);