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ISIS Application Documentation

histeq

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Apply histogram equalization to a cube.

Description
Categories
Groups
Examples
History

Description

This program equalizes the histogram of an input cube (defined by FROM), and outputs the results to a file (defined by TO).

By equalizing the input file's histogram, the resulting cumulative distribution becomes linear instead of curved. The following is an illustration of what happens to an input file. The blue line represents the histogram and the red line is the cumulative distribution. On the left is the histogram and cumulative distribution of an unmodified image, while the figure on the right shows how the both the histogram and distribution are altered.
Before equalization After equalization
The blue line represents the input file's histogram and the red line represents its cumulative distribution function.

Categories

Related Objects and Documents

Applications

Parameter Groups

Files

Name Description
FROM Input file to be equalized
TO Output cube

Histogram Options

Name Description
MINPERMinimum percentage
MAXPERMaximum percentage
INCREMENTPercentage increment

Files: FROM

Description

This file will have its cumulative distribution reshaped to be more linear.

Type cube
File Mode input
Filter *.cub

Files: TO

Description

The resultant cube containing a linearized image

Type cube
File Mode output
Filter *.cub

Histogram Options: MINPER

Description

Minimum DN cut-off value at the cumulative percent of the histogram

Type double
Default 0.5
Minimum 0.0 (inclusive)
Less Than
  • MAXPER

Histogram Options: MAXPER

Description

Maximum DN cut-off value at the cumulative percent of the histogram

Type double
Default 99.5
Maximum 100.0 (inclusive)

Histogram Options: INCREMENT

Description

Percentage increment for the histogram

Type integer
Default 1
Minimum 1 (inclusive)
Less Than
  • MAXPER

Examples

Example 1

Histogram equalization

Description

This example shows the results of histogram equalization on a single band of an image.

Command Line

histeq from=../peaks.cub+6 to=../result.cub
Use histogram equalization to the make the input cube's sixth band distribution function linear.

GUI Screenshot

Histeq Gui

Example Gui

Screenshot of GUI with parameters filled in to perform a histogram equalization operation with the input image.

Input Images

Input Peaks (band 6) Image

Input image for histeq

Parameter Name: FROM

This is band 6 of the input image for this example.

Input Peaks (band 6) Image

Band 6 histogram

This is the input image's cumulative distribution for band 6.

Output Images

Output image showing the result of the histogram equalization.

Output image for histogram equalization

Parameter Name: TO

This is the output image that results.

Output image

Resulting cumulative distribution

This is the output image's cumulative distribution.

History

Sean Crosby2006-12-15 Original version
Steven Lambright2008-05-06 Histogram object no longer has SetRange, updated to use SetValidRange
Steven Lambright2008-05-13 Removed references to CubeInfo
Tyler Wilson2015-09-03 Commented out a call to Histogram::SetValidRange(min,max) Because of changes made to the Histogram class. See Ref. #2188.