Yeah, it sounds like a color table problem. You probably are in a 256-size 8-bit-palette color-space and are trying to allocate 1000 unique colors. GD by default creates palette-based images. You need to either

1. create a TrueColor (24-bit RGB color) image, which requires a newer libgd and GD.pm. See GD.pm home manual under new(), trueColor() and newTrueColor() and search for palette.
2. or use colorResolve and colorClosest to map your 1000 objects into the 256 available palette slotes. Rather than use colorAllocation, I use colorResolve(@rgb)||colorClosest(@rgb) in my mk_color() utility function. Just don't let the table fill with 256 shades of brick red first.

The prior-comment about eval'ing trueColor to catch failure to make portable scripts take advantage of new features is right on target for your problem. (It's also a generalizable strategy for compatibility and extension for other modules and features, too.)

Good luck, enjoy -- I'm having fun with GD, hope you will too.

Bill n1vux
I had a .sig when they wasted usenet bandwidth, now I make it up as I go along.