2000.03.21 01:23 "raster scaling", by Scott&Patty

Hi all,

I realize that this post is a bit off topic, but I'm grasping at straws at this point.

The gist of my question is, "How do I _quickly_ scale down a monochrome image?" In particular, I want to preserve "on" pixels in large (~10k x ~10k pixels) images. I have seen a number of products that do this very well. "Zooming out" on a large image is practically instantaneous and the pixels are dithered to gray-scale resulting in very fine lines. While Wang Imaging (for Windows) is slow at load-time and memory heavy compared to some I've seen, it does do display of monochrome images like I'm interested in.

I've checked the Graphics Gems series, Foley and van Dam, and a number of the standard journals all to no avail. Am I missing something obvious?

I should probably state that I have of course tried optimizing the brute force method of checking every pixel that lies within the newly scaled pixel. As hard as I try to optimize, I am still _significantly_ slower than what I've seen (not to mention that I'm not even trying to generate gray level pixels based on the density of "on" pixels).

Thanks for any help (and please forgive my ignorance <g>).

Scott