[Mesa3d-users] osmesa offscreen rendering w/ grayscale for 10,800x14400 pic-possible?

[blake <cab...@ea...>]

I would like to use opengl and osmesa for rendering a single, large 
grayscale image that will then be saved to a file.  I downloaded 6.0.1 
and installed it.  I changed the config.h parameters, max_width, 
max_height to be 12,000 and 15000 and recompiled.  I can now make RGBA 
images using variations of the example code given in osdemo.c on my 
RedHat 8.0 system, but I get a 'segmentation violation' for images 
larger than 9,000 x 11,000.  Since I only need 256 colors of gray, I 
thought I would reduce the memory required by using a OSMESA_COLOR_INDEX 
rather than RGBA mode, which would then only require a memory allocation 
of 1 byte for a pixel versus 4 bytes per pixel of RGBA.  After changing 
the context to color_index, however, I found that calling glSetColor 
gave a segmentation fault.  Other variations also failed.  I am at a 
loss as to how to proceed.

Is it possible to run a color_index context with osmesa when you are 
using RedHat8.0 opengl? (I am confused about this-maybe if you are using 
an RGBA model to run your computer, you can't simultaneously create a 
color_index picture?)

Are there other ways to create a one byte gray level picture using 
opengl/mesa?  (Possibly you can't set the private color map with 
glSetColor?)

Any suggestions on where I might look for clues on solving this problem?

thanks
Blake