Making a texture from the currenct Mac OS X desktop/screen?


I’m writing a program and I’d like to mess with the a screen capture of whatever if displayed on the screen when the program starts. I need to then use the grab of the screen as an OpenGL texture so I can draw on it, or put it on a polygon or whatever.

So my question is, how do I grab the screen and then make it into a texture? It’s something I’ve done under Windows, but I can’t work it out under Mac OS X, altho I’m hoping it’s still possible.

Any help would be greatly appreciated!