Thanks, even if I'm not the one who asked. I guess the longer version of your answer would be "if you have larger input, just downscale first". And for the quality demands, you wouldn't even miss any antialiasing, just sample every nth pixel for a n00xn00 image, should really be good enough.

I wonder if it might be nice to allocate some more bytes to the center than to the edges/corners? Or is this already done?