Hi Janeen,
I cannot think of a way to do that, not in the renderer itself.
However, that would not be so hard to do with some external
drawing program, such as GIMP, which comes with Linux. By
"selecting contiguous regions", you should be able to separate
the background, and change it to white.
The renderer does not have any controls over what to display as
"background" values. And even if you store a list of those
images via "accumulate", the controls to alter the brightness,
colors, etc. do not affect them.
Sorry,
- rick
