
vhstr(1)                     Khoros                      vhstr(1)

PROGRAM
     vhstr - Performs histogram stretching of a BYTE grey-level
     image

SYNTAX
     vhstr

     -i             input image

     -o             resulting output image

     [-p]           invert image

     [-V]           Gives the version for vhstr

     [-U]           Gives the usage for vhstr

     [-P]           Prompts for command line options

     [-A [file1]]   Creates the answer file called vhstr.ans or
                    file1

     [-a [file1]]   Uses vhstr.ans or file1 as the answer file

DESCRIPTION
     vhstr performs a histogram stretch of the grey levels of a
     BYTE grey-level image. This is a contrast enhancement tech-
     nique that gives less harsh results that histogram equaliza-
     tion.

     The histogram stretch occurs over a range defined by
     integrating in from each end of the histogram until 1 per-
     cent of the cells have been found.  This prevents straggler
     channels from ruining the contrast.  The histogram within
     the 1 percent points is given a linear stretch mapping onto
     the full contrast range.

     The output image can be inverted using the -p photonegative
     argument.  This is useful when looking for faint features on
     a dark background, such as is often done with astronomical
     images.

REQUIRED ARGUMENTS
     -i     type: infile
            desc: input image

     -o     type: outfile
            desc: resulting output image

OPTIONAL ARGUMENTS
     -p     type: boolean
            desc: invert image
            default: false

EXAMPLES
     vhstr -i moon.xv -o moon.heq.xv -p 1

     will histogram stretch the image "moon.xv" and produce a
     photonegative output of that result in "moon.heq.xv".

SEE ALSO
     intro(1), verror(3), vgparms(3), vutils(3), lvhstr(3)
     vheq(1),vhisto(1),vhsee(1)

RESTRICTIONS
     vhstr operates only on BYTE images.

COPYRIGHT
     Copyright 1991, University of New Mexico.  All rights
     reserved.

Khoros                    Release: 1.0                          1

