Dov Kruger wrote:

Granted, because you are editing the image, not just displaying it,
there has to be some slowdown, but I wondered if there is any way I can
tweak gimp, do I somehow have it massively de-optimized. When I first
set up gimp-2.0, I tried both 128 and 512 Mb tile cache sizes. 512 seems
to work a lot better, but it's still pretty bad. Any idea as to the area
of the speed advantage of Adobe?

It's true that GIMP struggles with large images. I frequently need to edit 400 or even 600dpi full-colour A4 pages on a 256MB machine, and that's sailing pretty close to the wind.

The most important thing to do is balance your tile cache setting, as you've already found. You want it large enough that GIMP doesn't have to use its own virtual memory, but not so large that the OS has to use virtual memory to accommodate it. On a 2GB machine, I'd set to about 1.5GB, assuming GIMP has pretty much free reign over the machine.

The other thing that can help a lot is to set the maximum number of undo levels right down to 1, but set the maximum undo memory to something a bit higher - maybe 50 or 100 MB. That way you still get plenty of undo levels on small images, but don't waste memory with a long undo history for huge images. I've found that this solves most of the disk thrashing problems with GIMP/Win98 and A4 scans. Linux seems to have better memory management to start with, but this tweak can help here too.

All the best,
Alastair M. Robinson
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