RETRO commands


PROGRAM NAME

vhxray - Stretch or Equalize Histogram Using Overlapping Windows (K1)

DESCRIPTION

vhxray will enhance an image by using a histogram stretch or histogram equalization method. Vhxray will use overlapping windows over the entire image, and for each window compute the histogram and perform a stretch or equalization. The middle pixel of the window is updated according to the new histogram value that corresponds to the old image pixel values.

The window size must be odd (3x3, 5x5, 15x15, etc), since we must have a center pixel to update for each window. The default window size is 5x5.

The input image must be of type BYTE. The default operation is to use the histogram equalization method (-t = 1).

Since windows are being used, the border pixels will not be updated. The border pixels will be set to zero, black. The border size can be calculated as follows: window width / 2 = side border, window height /2 = top & bottom border.

A large window size will give better results than a small window size. For example a window size of 33 x 33 on a 512 x 512 image will give better results than a window size of 5 x 5 on the same image.

REQUIRED ARGUMENTS

-i
type: infile
desc: first input image
-o
type: outfile
desc: resulting output image

OPTIONAL ARGUMENTS

-w
type: integer
desc: selects the width of the window
default: 5
bounds: 1 < [-w] < 32
-h
type: integer
desc: selects the height of the window
default: 5
bounds: 1 < [-h] < 32
-t
type: boolean
desc: Choose Histogram Stretch (true) or Equalization (false)
default: false

EXAMPLES

vhxray -i input.image -o output.image -w 9 -h 9 -t 0

This command performs image enhancement on input image using histogram equalization and stores the result in output.image. The size of the window used is 9 by 9.

SEE ALSO

khistops, khstr, kheq

RESTRICTIONS

vhxray Will only operate on BYTE images. The image border is not updated as explained above.

REFERENCES

COPYRIGHT

Copyright (C) 1993 - 1997, Khoral Research, Inc. ("KRI") All rights reserved.