don't see how that could help
You're absolutely right.
Without any images (or the chance to sub them for my own) or the include code I have no chance of running this and providing feedback on whether I see the issue on my machines, what their spec is, add debug/timing/memory usage code etc and help you out.
So...
Why don't you add debug messages to your code so you can determine which function/method is causing the slowdown?