All flags can be abbreviated to their shortest unique prefix. If no
file type is specified the most highly constained compatible type is
used, where monochrome is more constained than colormapped which is in
turn more constained than unmapped.
Forces Targa file to be of type 8 bit monochrome. Input must be a portable
bitmap or a portable graymap.
Forces Targa file to be of type 24 bit colormapped. Input must be a portable
bitmap, a portable graymap or a portable pixmap containing no more than
256 distinct colors.
Forces Targa file to be of type 24 bit unmapped color.
Disables run-length encoding, in case you have a Targa reader which
cant read run-length encoded files.