The <a definition for P6</a> states that  <i>maxval</i> can be up to 65535, with <i>maxval</i>s &gt; 255 indicating that 2 bytes per channel per pixel are to be used (instead of 1).<p>We should fix (though we will lose information; Tk uses strictly 32 bits per pixel, with 8 for each of R, G, B, and alpha). Priority not very high as this is a fairly rare format variation (and we'll never write it from photo images), but the changes should at least be quite localised to just the PPM format handler.