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opening and display large file

How do you manage to display very large images? What is the options?
From the manual, it seem that using "assoc" is a winner but maybe with one little example it would be more clear how can this be (It seem to me that it is an important aspect of programming with IDL since most of the time you'll deal with larger than memory files).
Even with assoc, dont you still have to copy from the file to an array before display?
I dont decipher exactly why and when to use readu or read_binary, the file pointer, assoc or writing to an offscreen buffer.

I tried to open and display a GTOPO30 tile (4800 x 6000 int). tv could not display it - froze. I tried "slide_image" but it didnt scroll with "retain=1" while "retain=2" and "retain=3" result in windows error and crash.

Since most of my data fall in the 30mb to 610 mb range, I need absolutely to open and display very large file. What is available? Pointers, sample code, library, ideas, etc, I'm listening.... Just knowing that it have to be handled on your own or that IDL provide facility (that they forgot to explain in the manual) to deal with this will already be invaluable


Sylvain Carette
VRML designer-composer