Level 2 Help for HISTGEN

 Input image in byte or 16-bit integer (halfword) data format.

The histogram is output as an IBIS tabular file containing one column and
MAXD+4 rows.  The data is stored in INTEGER*4 format as follows:

    Column 1 = Number of DN levels in the histogram (=MAXD+1)
    Column 2 = 1000*meanDN
    Column 3 = 1000*standard-deviation
    Column 4 = Number of pixels at 0 DN or lower
    Column 5 = Number of pixels at 1 DN
    Column 6 = Number of pixels at 2 DN
      .
      .
      .
    Column MAXD+4 = Number of pixels at MAXD DN or higher

 Standard VICAR size parameter, specifying the area of the input image to be
 used to generate the histogram.

 Specifies the maximum DN in the output histogram.  I.e., the histogram will
 have a DN range from 0 to MAXD DN.   Default is 255 for byte, 32767 for
 halfword.