Should support RGB / RGB_ALPHA / GRAYSCALE correctly, though Change-Id: Idb1470581ebdfc6efee73009b2abd53889e901cb
see spec: http://netpbm.sourceforge.net/doc/ppm.html Change-Id: I55e01f8cec79f9124e72d5f3d05be4ad0deae315
see: http://netpbm.sourceforge.net/ Only reads P5 and P6 pnm files for now. Change-Id: I2332a623f803df67455047f570f1cff9f464480a