/usr/share/gnudatalanguage/coyote/histomatch.pro is in gdl-coyote 2016.11.13-2.
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; NAME:
; HistoMatch
;
; PURPOSE:
;
; This is a function for Histogram Matching, in which an image
; is manipulated in such a way that it's final histogram approximates
; the histogram of an input image or histogram. Histogram matching
; allows the user to specify the shape of the histogram of the final
; product.
;
; AUTHOR:
;
; FANNING SOFTWARE CONSULTING
; David Fanning, Ph.D.
; 1645 Sheely Drive
; Fort Collins, CO 80526 USA
; Phone: 970-221-0438
; E-mail: david@idlcoyote.com
; Coyote's Guide to IDL Programming: http://www.idlcoyote.com
;
; CATEGORY:
;
; Image Processing
;
; CALLING SEQUENCE:
;
; output_image = HistoMatch(image, histogram_to_match)
;
; INPUTS:
;
; image - The input image to be manipulated. Assumed to be a 2D byte array.
;
; histogram_to_match - Can be either a 1D long vector of 256 elements specifying
; the histogram to match, or a 2D byte array from which the histogram to
; match is calculated.
;
; OUTPUTS:
;
; output_image - The manipulated image adjusted to the histogram specifications.
;
; INPUT KEYWORDS:
;
; None.
;
; OUTPUT KEYWORDS:
;
; None.
;
; DEPENDENCIES:
;
; None.
;
; METHOD:
;
; Based on the Histogram Matching method on pages 94-102 of Digital
; Image Processing, 2nd Edition, Rafael C. Gonzalez and Richard E. Woods,
; ISBN 0-20-118075-8.
;
; EXAMPLE:
;
; There is an example program at the end of this file. It will require cgImage
; from the Coyote Library to run. You can also find an explanation of this program
; at http://www.idlcoyote.com/ip_tips/histomatch.html.
;
; MODIFICATION HISTORY:
;
; Written by David W. Fanning, January 2003.
;-
;
;******************************************************************************************;
; Copyright (c) 2008, by Fanning Software Consulting, Inc. ;
; All rights reserved. ;
; ;
; Redistribution and use in source and binary forms, with or without ;
; modification, are permitted provided that the following conditions are met: ;
; ;
; * Redistributions of source code must retain the above copyright ;
; notice, this list of conditions and the following disclaimer. ;
; * Redistributions in binary form must reproduce the above copyright ;
; notice, this list of conditions and the following disclaimer in the ;
; documentation and/or other materials provided with the distribution. ;
; * Neither the name of Fanning Software Consulting, Inc. nor the names of its ;
; contributors may be used to endorse or promote products derived from this ;
; software without specific prior written permission. ;
; ;
; THIS SOFTWARE IS PROVIDED BY FANNING SOFTWARE CONSULTING, INC. ''AS IS'' AND ANY ;
; EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES ;
; OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT ;
; SHALL FANNING SOFTWARE CONSULTING, INC. BE LIABLE FOR ANY DIRECT, INDIRECT, ;
; INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED ;
; TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; ;
; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ;
; ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT ;
; (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS ;
; SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. ;
;******************************************************************************************;
FUNCTION HISTOMATCH, image, histogram_to_match
; Error handling.
Catch, theError
IF theError NE 0 THEN BEGIN
Catch, /Cancel
ok = cgErrorMsg(/Traceback)
IF N_Elements(image) NE 0 THEN RETURN, image ELSE RETURN, -1L
ENDIF
; We require two input parameters.
IF N_Params() NE 2 THEN Message, 'Two arguments required. Please read the program documentation.'
; Must have 2D image array.
IF Size(image, /N_Dimensions) NE 2 THEN Message, 'Image argument must be 2D. Returning.'
; Is the histogram_to_match variable a 1D or 2D array? Branch accordingly.
CASE Size(histogram_to_match, /N_Dimensions) OF
1: BEGIN
IF N_Elements(histogram_to_match) NE 256 THEN $
Message, 'Histogram to match has incorrect size. Returning.'
match_histogram = histogram_to_match
END
2: match_histogram = Histogram(Byte(histogram_to_match), Min=0, Max=255, Binsize=1)
ELSE: Message, 'Histogram to match has incorrect number of dimensions. Returning.'
ENDCASE
; Calculate the histogram of the input image.
h = Histogram(Byte(image), Binsize=1, Min=0, Max=255)
; Make sure the two histograms have the same number of pixels. This will
; be a problem if the two images are different sizes, you are matching a
; histogram from an image subset, etc.
totalPixels = Float(N_Elements(image))
totalHistogramPixels = Float(Total(match_histogram))
IF totalPixels NE totalHistogramPixels THEN $
factor = totalPixels / totalHistogramPixels ELSE $
factor = 1.0
match_histogram = match_histogram * factor
; Find a mapping from the input pixels to the transformation function s.
s = FltArr(256)
FOR k=0,255 DO BEGIN
s[k] = Total(h(0:k) / totalPixels)
ENDFOR
; Find a mapping from input histogram to the transformation function v.
v = FltArr(256)
FOR q=0,255 DO BEGIN
v[q] = Total(match_histogram(0:q) / Total(match_histogram))
ENDFOR
; Find probablitly density function z from v and s.
z = BytArr(256)
FOR j=0,255 DO BEGIN
i = Where(v LT s[j], count)
IF count GT 0 THEN z[j] = (Reverse(i))[0] ELSE z[j]=0
ENDFOR
; Create the matched image.
matchedImage = z[Byte(image)]
RETURN, matchedImage
END
; ----------------------------------------------------------------------------
PRO Example
; Get an image whose histogram you want to match.
filename = Filepath('ctscan.dat', Subdir=['examples', 'data'])
OpenR, lun, filename, /Get_Lun
image_to_match = BytArr(256, 256)
ReadU, lun, image_to_match
Free_Lun, lun
; Get an image to apply the histogram to.
filename = Filepath('worldelv.dat', Subdir=['examples', 'data'])
OpenR, lun, filename, /Get_Lun
image = BytArr(360, 360)
ReadU, lun, image
Free_Lun, lun
Window, 0, XSize=500, YSize=250, Title='Match this Image Histogram', XPos=100, YPos=100
!P.Multi=[0,2,1]
cgImage, image_to_match
Plot, Histogram(image_to_match), Max_Value=5000
!P.Multi=0
Window, 1, XSize=500, YSize=250, Title='Manipulate this Image', XPos=100, YPos=360
!P.Multi=[0,2,1]
cgImage, image
Plot, Histogram(image), Max_Value=5000
!P.Multi=0
Window, 2, XSize=500, YSize=250, Title='Final Result', XPos=100, YPos=630
!P.Multi=[0,2,1]
match = HistoMatch(image, image_to_match)
cgImage, match
Plot, Histogram(match), Max_Value=5000
!P.Multi=0
END
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