I'm using cairo but have run into a snag. I want to load a raster image (a .png file) and then use that image as a mask. The image I am loading is black, and I would like to use it as clipping mask, or regular mask and 'stamp' so that I could change the image from black to another color (or gradient.) Pseudo-code or comments greatly appreciated. And this for my own project, not homework. Thanks.