/usr/share/gnudatalanguage/coyote/checkerboard.pro is in gdl-coyote 2016.11.13-2.
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; NAME:
; Checkerboard
;
; PURPOSE:
; This function returns a 2D image, with boxes of alternating colors.
; Checkerboard images are useful in certain types of image processing
; procedures and for making blended image masks.
;
; 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:
;
; board = Checkerboard()
;
; RETURN VALUE:
;
; board: A 2D long array of alternating colored boxes.
;
; ARGUMENTS:
;
; boxes: The number of boxes of alternating colors on each side
; of the resulting image. Must be an even integer greater
; than or equal to two. Optional. Default is 8 (normal
; checkerboard).
;
; INPUT KEYWORDS:
;
; BLACK: The value of the "black" boxes. By default, 0.
;
; WHITE: The value of the "white" boxes. By default, 255.
;
; XSIZE: The X size of the returned image. By default, 400.
;
; YSIZE: The Y size of the returned image. By default, 400.
;
; COMMON BLOCKS:
;
; None.
;
; EXAMPLE:
;
; IDL> cgImage, Checkerboard()
;
; MODIFICATION HISTORY:
;
; Written by David W. Fanning, 26 September 2007, based on suggestions
; of JD Smith on IDL newsgroup 25-26 Septermber 2007.
;-
;
;******************************************************************************************;
; 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 Checkerboard, boxes, WHITE=white, BLACK=black, XSIZE=xsize, YSIZE=ysize
ON_ERROR, 2 ; Return to caller
IF N_Elements(boxes) EQ 0 THEN boxes = 8 ELSE boxes = Long(boxes) > 2L
IF boxes MOD 2 NE 0 THEN boxes = boxes + 1L
IF N_Elements(white) EQ 0 THEN white = 255B
IF N_Elements(black) EQ 0 THEN black = 0B
IF N_Elements(xsize) EQ 0 THEN xsize = 400L
IF N_Elements(ysize) EQ 0 THEN ysize = 400L
;; Alternating 0s and 1s.
array = LIndGen(boxes, boxes)
board = ( (array MOD 2) LT 1 ) XOR ( ((array / boxes) MOD 2) GE 1 )
;; Make sure colors are correct.
whitePixels = Where(board EQ 0, COMPLEMENT=blackPixels)
board[whitePixels] = white
board[blackPixels] = black
RETURN, Congrid(board, xsize, ysize)
END
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