The -scale flag controls the scale of the result. The default scale is 1, which results in one pgm pixel producing a 3x3 square of PostScript pixels. On a 300 dpi printer such as the Apple LaserWriter, this makes the output look about the same size as the input would if it was displayed on a typical 72 dpi screen. To get one pgm pixel per LaserWriter pixel, use "-s 0.333333".
The -rle flag specifies run-length compression. This may save time if the host-to-printer link is slow; but normally the printer's processing time dominates, so -rle makes things slower.
All flags can be abbreviated to their shortest unique prefix.
Note that there is no pstopgm tool - this transformation is one-way, because a pstopgm tool would be a full-fledged PostScript interpreter, which is beyond the scope of this package. However, see the psidtopgm tool.
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