For some reason when piping the output of pnmtops directly to ps2pdf,
conversion is very slow (especially for color scans).
When writing to an intermediate temporary file, conversion is fast.
Before:
________________________________________________________
Executed in 19.20 secs fish external
usr time 4.01 secs 0.32 millis 4.01 secs
sys time 20.63 secs 5.30 millis 20.62 secs
After:
________________________________________________________
Executed in 368.06 millis fish external
usr time 378.06 millis 0.00 millis 378.06 millis
sys time 100.00 millis 2.79 millis 97.21 millis
An improvement of over 50 times!
This should resolve#19.
