imwrite with unicode path Windows

Hi Is there any way in Windows MFC to give a non-ascii file name to imwrite? cv::String appears to be internally represented by char*and Unicode in Windows is UTF-16. Is there a way to convert an UTF-16 string to UTF-8 and put it in a char array? I thought chars in Windows only represents the ascii set? I'm not the best at encoding so I'm wondering if anyone else has solved this Thanks