Converts an image to raw pgm format.
Results go to stdout and should be redirected.
Usage: mritopgm [-pp] input_image
Example: mritopgm fred.001 | ppmtogif > fred.001.gif
The '-pp' option expresses a clipping percentage.
That is, if this option is given, the pp%-brightest
pixel is mapped to white; all above it are also white,
and all below are mapped linearly down to black.
The default is that pp=100; that is, the brightest
pixel is white. A useful operation for many MR images is
mritopgm -99 fred.001 | ppmtogif > fred.001.gif
This will clip off the top 1% of voxels, which are often