GD has always served my needs till now; but the recent news of libgd stagnation made me make a mental note to look at other options. I tried I::M once and found it to be a huge messy things; 'sides I couldn't possibly bring myself to use anything that spelt magic with a 'k' :)

I just found Imager available as a PPM for 64-bit, so, I installed that. I obviously can't yet comment upon it's abilities. Seems quite large at 142 files. But, at a cursory glance, it also seems to be very well structured and documented, and that is half the battle.