There's a fair bit of software for modifying images from Photoshop to Maxim and the list is pretty long actually. You might also want to stop by Dave Allmon's website and check out the DARKGEN software he has. He's available though the QCUIAG website http://www.astrabio.demon.co.uk/QCUIAG/ I believe is it's address is. Dave's website is http://ns.par1.net/~dallmon and you will need to look in his software section. Don't forget to also download his runtime part if you do get his software. I haven't run it but it's a work in progress and you may have to do a format conversion as I think that he uses the BMP format for input and output. It's free so don't be afraid to at least try it.