xicc/specplot
    Summary
    A simple tool to plot spectrum files (.sp, .cmf, .ccss etc.), and
    compute the  CCT and VCT, CRI, TLCI, XYZ, x,y and L*a*b*
    values.
    Usage summary
    
    specplot [infile1.sp,
          infile2.sp, ...]
     -v              
      verbose
     -c              
      combine multiple files into one plot
       -n              
      normalize max level
     -z              
don't
      make range cover zero
       -s              
      don't plot spectra
       -d I|A|M|T|E     print density values
     -u
      level         plot effect
      of adding estimated UV level
     -U              
      plot effect of adding range of estimated UV level
     [infile.sp ...]  spectrum files to plot
                     
      default is all built in illuminants
    
    Usage Details and Discussion
    Run without an argument,
    each built in illuminant is plotted in turn. If an argument is
    given, then just that
    spectrum will be plotted. 
    
    Hit a key in the plot window to advance to the next spectrum.
    
    If the -p option is set, then no plot is shown.
    
    The -d option will select the type of density measurement to
    print, if the value is a reflective or transmissive measurement:
        I = ISO Visual, 1 & 2 + Visual 
        A = Status T + Visual
        M = Status M + Visual
        T = Status T + Visual
        E = Status E + Visual