Speeding up this handler

[Geoff Canyon]

You should first break down the problem to see what is slow. Off the 
top of my head, possibilities include:

1. Updating images onscreen. (even though the screen is locked)
2. Loading data from a file.
3. Getting the data into an image.
4. The code you wrote to do 1,2, and 3.

2 and 3 are tough to separate since they're both part of

       set the filename of image bMap[z] to line y of cMap[x]

First, try timing setting the filename of an image repeatedly to two 
different files. See how long that takes. I'd bet you'll find that it 
takes 99% of the time the routine you posted takes. In other words, the 
overhead is all in setting the images, not in the routine you wrote to 
do it.

If that's the case, you need to figure out what's slow among 1, 2, and 
3.

Second, create two source images, and try timing setting the imagedata 
of  a third image repeatedly to the two source images, a, then b, then 
a, etc. That should give you a good idea whether 1 and 3 are your 
problem.

If 1 and 3 are the problem, try timing setting the icon of a button to 
the two images, see if that is any faster.

If 1 and 3 aren't the problem, then consider 2. Others have suggested 
ways of using images as a storage method. You might also simply store 
the image data in an array. I don't know what the memory and 
performance overhead is on an image that you never display, but it has 
to be higher than an array (I think).

regards,

Geoff Canyon
gcanyon at inspiredlogic.com