separate a portable pixmap into three portable graymaps
see also :
rgb3toppm - ppmtopgm - pgmtoppm
add an example, a script, a trick and tips
no example yet ...
... Feel free to add your own example above to help other Linux-lovers !
portable pixmap as input. Writes three portable graymaps as
output, one each for red, green, and blue.
filenames are constructed by taking the input filename,
stripping off any extension, and appending ".red",
".grn", and ".blu". For example,
separating lenna.ppm would result in lenna.red, lenna.grn,
and lenna.blu. If the input comes from stdin, the names are
noname.red, noname.grn, and noname.blu.
ppmtopgm , pgmtoppm , ppm, pgm
1991 by Jef Poskanzer.