Expose event of displaying large image

[Justin Zhang <bnj8754777 jlonline com>]

In my programe, I want to load in PGM type of image files. I use strings
to store the pixel values. If the size of the image file is too large,
the whole file cannot be loaded
into one string (since the memory is also limited ). So whenever  an
expose takes place, the whole file must be loaded in again ( it cannot
be stored in the main memory ) and redrawn. I wonder if there is a
method more efficient. I donn't know
whether the system supports a 'virtuel memory' function so that I can
creat a pixmap
large enough to store the pixels (extra part to be stored on hard disk )
? If so, I
think it may become easier.

    Thanks

Justin Zhang