I you got photoshop it gets even better if you use the black mask just drag the entire masked image on top and set that layer to screen. If you use the white mask same idea but use darken intead. No cuttting nessesary. Sometimes you have to put somthing under to keep the colors from going slightly transparent. Like a black mask. Save those Alpha channels! You can invert it if you need it the other way. If something your doing seems complicated there is a easier way....