Utility for extracting the colour map from a png or gif file

Image should be cropped and rotated so that it contains only the
colourbar in a horizontal format (i.e. with colours changing from
left to right)

Requires netpbm tools to first convert image to plain ppm format

Fortran code then quantizes the colour map to a small table of
interpolation points in (l, red, green, blue) where l is the
position in the interpolation table (0-1) and r,g,b are the
colours at that position, where linear interpolation should
be used between the points

To use the interactive quantization tool you need the
giza plotting library installed (http://giza.sf.net)

Output is currently a Fortran table suitable for
incorporation in the SPLASH visualisation tool
(http://users.monash.edu.au/~dprice/splash)

Written by Daniel Price 2005-2018