I'm don't follow what you mean by "semi-transparent background", and your code is a little too lengthy and messy for me to want to tear apart. However, FWIW I have managed to get GD to print black text on top of a patterned background, and the text blended correctly with the background -- i.e. when the vector (font) graphic was layered on top of the raster image, the anti-aliasing algorithm used the pixels from the patterned background rather than white or something else. Have you managed to do something simple like that? If so, then we can limit the problem domain to something small and go from there.