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cggmascl.pro
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; docformat = 'rst'
;
; NAME:
; cgGmaScl
;
; PURPOSE:
; This is a utility routine to perform basic gray-level pixel transformations of images.
; I think of it as BYTSCL on steroids. It is similar to IMADJUST in _Digital Image
; Processing with MATLAB_ by Gonzales, Wood, and Eddins. It performs a log scaling
; of the image array.
;
;******************************************************************************************;
; ;
; Copyright (c) 2015, 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. ;
;******************************************************************************************;
;
;+
; This is a utility routine to perform basic gray-level pixel transformations of images.
; I think of it as BYTSCL on steroids. It is similar to IMADJUST in _Digital Image
; Processing with MATLAB_ by Gonzales, Wood, and Eddins. It performs a log scaling
; of the image array.
;
; :Categories:
; Image Processing
;
; :Returns:
; A byte scaled image is returned.
;
; :Params:
; image: in, required
; The image to be scaled. Written for 2D images, but arrays of any size are treated alike.
;
; :Keywords:
; gamma: in, optional, type=float, default=1.0
; The exponent in a power-law transformation (image^gamma). A gamma value of 1 results in
; a linear distribution of values between OMIN and OMAX. Gamma values less than 1 map
; darker image values into a wider range of output values, and Gamma values greater than
; 1 maps lighter image values into a wider range of output values. The gamma value is
; constrained to be greater than 1.0e-6.
;
; max: in, optional
; Any value in the input image greater than this value is set to this value
; before scaling.
;
; min: in, optional
; Any value in the input image less than this value is set to this value
; before scaling.
;
; negative, in, optional, type=boolean, default=0
; If set, the "negative" of the result is returned.
;
; omax: in, optional, type=byte, default=255
; The output image is scaled between OMIN and OMAX.
;
; omin: in, optional, type=byte, default=0
; The output image is scaled between OMIN and OMAX.
;
; :Examples:
; cgLoadCT, 0 ; Gray-scale colors.
; image = cgDemoData(11) ; Load image.
; TVImage, cgGmaScl(image, Min=30, Max=100) ; Similar to BytScl.
; TVImage, cgGmaScl(image, /Negative) ; Produce negative image.
; power = Shift(ALog(Abs(FFT(image,-1))), 124, 124) ; Create power spectrum.
; TVImage, cgGmaScl(power, Gamma=2.5) ; View power specturm with gamma correction.
; TVImage, cgGmaScl(power, Gamma=2.5, /Negative) ; Reverse power spectrum.
;
; :Author:
; FANNING SOFTWARE CONSULTING::
; David W. Fanning
; 1645 Sheely Drive
; Fort Collins, CO 80526 USA
; Phone: 970-221-0438
; E-mail: [email protected]
; Coyote's Guide to IDL Programming: http://www.idlcoyote.com
;
; :History:
; Change History::
; Written by: David W. Fanning, 17 February 2006.
; Fixed a problem with output scaling. 1 July 2009. DWF (with input from Bo Milvang-Jensen).
; Now setting NAN keyword on all MIN and MAX functions. 2 Dec 2011. DWF.
; Renamed cgGmaScl from GmaScl. 27 March 2015. DWF.
;
; :Copyright:
; Copyright (c) 2006-2015, Fanning Software Consulting, Inc.
;-
FUNCTION cgGmaScl, image, $
GAMMA=gamma, $
MAX=imageMax, $
MIN=imageMin, $
NEGATIVE=negative, $
OMAX=maxOut, $
OMIN=minOut
; Return to caller on error.
;On_Error, 2
Catch, theError
IF theError NE 0 THEN BEGIN
Catch, /Cancel
void = cgErrorMsg()
RETURN, vector
ENDIF
; Check arguments.
IF N_Elements(image) EQ 0 THEN Message, 'Must pass IMAGE argument.'
; Check for underflow of values near 0. Yuck!
curExcept = !Except
!Except = 0
i = Where(image GT -1e-35 AND image LT 1e-35, count)
IF count GT 0 THEN image[i] = 0.0
void = Check_Math()
!Except = curExcept
output = Double(image)
; Check keywords.
IF N_Elements(imageMax) EQ 0 THEN imageMax = Max(output, /NAN)
IF N_Elements(imageMin) EQ 0 THEN imageMin = Min(output, /NAN)
IF N_Elements(maxOut) EQ 0 THEN maxOut = 255B ELSE maxout = 0 > Byte(maxOut) < 255
IF N_Elements(minOut) EQ 0 THEN minOut = 0B ELSE minOut = 0 > Byte(minOut) < 255
IF minOut GE maxout THEN Message, 'OMIN must be less than OMAX.'
; Gamma must be greater than 0.
IF N_Elements(gamma) EQ 0 THEN gamma = 1.0D ELSE gamma = 1.0e-6 > Double(gamma)
; Perform initial scaling of the image.
output = cgScaleVector(Temporary(output), 0.0D, 1.0D, MinValue=imageMin, MaxValue=imageMax, /NAN, Double=1)
; For gamma, we need positive values. Make sure we have them
IF Min(output, /NAN) LT 0.0D THEN output = output + Abs(Min(output, /NAN))
output = cgScaleVector(output^gamma, minOut, maxOut, MinValue=0.0D, MaxValue=1.0D, /NAN, Double=1)
; Does the user want the negative result?
IF Keyword_Set(negative) THEN RETURN, BYTE(0B > (maxout - Round(output) + minOut) < 255B) $
ELSE RETURN, BYTE(0B > Round(output) < 255B)
END