;+ ; NAME: ; CLIPSCL ; ; PURPOSE: ; ; This is a utility routine to perform linear scaling (similar to BYTSCL) ; on image arrays. If differs from BYTSCL only in that a user-specified ; percentage of pixels can be clipped from the image histogram, prior to ; scaling. By default, two percent of the pixels are clipped. Clipping ; occurs at both ends of the image histogram. ; ; 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: ; ; Utilities ; ; CALLING SEQUENCE: ; ; scaledImage = CLIPSCL(image, clipPercent) ; ; ARGUMENTS: ; ; image: The image to be scaled. Written for 2D images, but arrays ; of any size are treated alike. ; ; clipPercent: The percent of image clipping. Optional argument is set ; to 2 by default. Must be value between 0 and 49. Clipping ; occurs from both ends of image histogram, so a clip of 2 ; linearly scales approximately 96% of the image histogram. ; Clipping percents are approximations only, and depend ; entirely on the distribution of pixels in the image. For ; interactive scaling, see cgStretch. ; ; INPUT KEYWORDS: ; ; ; NEGATIVE: If set, the "negative" of the result is returned. ; ; OMAX: The output image is scaled between OMIN and OMAX. The ; default value is 255. ; ; OMIN: The output image is scaled between OMIN and OMAX. The ; default value is 0. ; OUTPUT KEYWORDS: ; ; ; THRESHOLD: A two-element array containing the image thresholds for clipping. ; ; RETURN VALUE: ; ; scaledImage: The output, scaled into the range OMIN to OMAX. A byte array. ; ; COMMON BLOCKS: ; None. ; ; EXAMPLES: ; ; LoadCT, 0 ; Gray-scale colors. ; image = cgDemoData(22) ; Load image. ; TV, ClipScl(image, 4) ; ; RESTRICTIONS: ; ; Requires cgScaleVector from the Coyote Library: ; ; http://www.idlcoyote.com/programs/cgScaleVector.pro ; ; MODIFICATION HISTORY: ; ; Written by: David W. Fanning, 6 September 2007. ; Not sure what this program was doing, but not what I thought. I've reworked ; the algorithm to scale the data appropriately. 25 Oct 2011. DWF. ;- ;******************************************************************************************; ; 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 ClipScl, image, clip, $ NEGATIVE=negative, $ OMAX=maxOut, $ OMIN=minOut, $ THRESHOLD=threshold ; 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.' IF N_Elements(clip) EQ 0 THEN clip = 2 ELSE clip = 0 > clip < 48 ; 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 = image ; Check keywords. 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.' ; Calculate binsize. maxr = Max(image, MIN=minr, /NAN) range = maxr - minr IF Size(image, /TName) EQ 'BYTE' THEN binsize = 1.0 ELSE binsize = range / 1000. IF Size(image, /TName) NE Size(binsize, /TName) THEN image = Convert_To_Type(image, Size(binsize, /TName)) h = Histogram(image, BINSIZE=binsize, OMIN=omin, OMAX=omax, /NAN) n = N_Elements(image) cumTotal = Total(h, /CUMULATIVE) minIndex = Value_Locate(cumTotal, n * (clip/100.)) IF minIndex EQ -1 THEN minIndex = 0 WHILE cumTotal[minIndex] EQ cumTotal[minIndex + 1] DO BEGIN minIndex = minIndex + 1 ENDWHILE minThresh = minIndex * binsize + omin ; Not all files can be clipped appropriately. If maxIndex ; is -1 or N_Elements(cumTotal), or maxIndex=minIndex then ; just byte scale the image and get out of here. maxIndex = Value_Locate(cumTotal, n * ((100-clip)/100.)) IF (maxIndex EQ -1) || (maxIndex EQ N_Elements(cumTotal)) || (maxIndex EQ minIndex) THEN BEGIN threshold = [minr, maxr] Message, 'Image histogram could not be clipped successfully. Image is byte scaled.', /Informational IF Keyword_Set(negative) THEN RETURN, 255B - BytScl(image, /NAN) ELSE RETURN, BytScl(image, /NAN) ENDIF ; If you are still here, try to clip the histogram. WHILE cumTotal[maxIndex] EQ cumTotal[maxIndex - 1] DO BEGIN maxIndex = maxIndex - 1 ENDWHILE maxThresh = maxIndex * binsize + omin ; Save the thresholds. threshold = [minThresh, maxThresh] ; Scale the data. output = cgScaleVector(Temporary(output), MIN=threshold[0], MAX=threshold [1], minOut, maxOut) IF Keyword_Set(negative) THEN RETURN, 0B > (maxout - output + minOut) < 255B $ ELSE RETURN, output END