A slightly more narrow approach to BrowserUk's questions above: are you saving anything as a JPEG? If so, you almost certainly shouldn't be—GD is a terrific tool for 8-bit graphic manipulation, but 8-bit JPEGs are not generally especially pleasant to look upon, and things that should be 8-bit GIFs or PNGs, when saved as JPEG, look fuzzy and are larger than the GIF or PNG would be.