; docformat = 'rst' ; ; NAME: ; cgLineIntersect ; ; PURPOSE: ; This function returns the intersection of two line segments, represented by four points. ; ;******************************************************************************************; ; ; ; Copyright (c) 2014, 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 function returns the intersection of two line segments, represented by four points. ; ; :Categories: ; Utilities ; ; :Params: ; x0: in, required ; The x location of the one end of the first line segment. ; y0: in, required ; The y location of the one end of the first line segment. ; x1: in, required ; The x location of the other end of the first line segment. ; y1: in, required ; The y location of the other end of the first line segment. ; x2: in, required ; The x location of the one end of the second line segment. ; y2: in, required ; The y location of the one end of the second line segment. ; x3: in, required ; The x location of the other end of the second line segment. ; y3: in, required ; The y location of the other end of the second line segment. ; ; :Author: ; FANNING SOFTWARE CONSULTING:: ; David W. Fanning ; 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 ; ; :History: ; Change History:: ; Written, 10 September 2014 on suggestion of Wang Kang. ; ; :Copyright: ; Copyright (c) 2014, Fanning Software Consulting, Inc. ;- FUNCTION cgLineIntersect, x0, y0, x1, y1, x2, y2, x3, y3 param1 = LINFIT([x0, x1], [y0, y1]) param2 = LINFIT([x3, x2], [y3, y2]) x = [[param1[1]*(-1.), 1.],[param2[1]*(-1.), 1.]] b = [[param1[0]],[param2[0]]] intersection = b # Invert(x) RETURN, intersection END