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variable: $tiffoutflag -- tiff vs. rgb
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default: 1 (TRUE)

The unlabeled tickbox on the "rgb:" entry line
controls bitmap output file format.

When tiffoutflag is 1 (ticked, the default), the
bitmap output file format is a 3 bytes per pixel,
LZW compressed, tiff file.  If tiffoutflag is 0
(unticked), the original SGI rgb bitmap format
(uncompressed) is used instead.
