Saving Screen to file

[Brent L. Bates AAD/TAB MS361 x42854]

     I would like to be able to save the entire screen (or part of it)
to a file of my own format.  It shouldn't matter what mode the windows
are in, RGB or color map, I want the RGB values no matter what mode the
window is in. That way if I have a window in RGB mode and one in color
map mode I can save the entire screen as RGB values.
     I have looked at 4Dgifts/iristools/imgtools and there is one utility
to save the screen, that is scrsave.  Scrsave calls an undocumented
function gl_readscreen.  What library is this routine in?  Why isn't it
documented?  It seems to be the only function that will do what I want,
however there is no documentation.  Is it ok to use this function or will
it disappear some day.  It should be a normal library function, complete
with documentation.
     I have tried using other routines with no success.  Any suggestions?
Most of this is aimed at SGI.
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					Brent