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 technique that gives less harsh results that histogram equalization.

The histogram stretch occurs over a range defined by integrating in from each end of the histogram until 1 percent 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.