How to generate bitmaps containing truetype fonts?

I'd like to build a script that generates bitmaps for a navigation bar. I only reached to draw post script fonts and to write a .png file. But I'd like to use true type fonts instead and to write the bitmaps as .gif files. Can anybody give me a hint? Is there a tool that converts .pngs to .gifs? Is it possible to use truetypes? Thanks!