isPointInPolygon

ISPOINTINPOLYGON Test if a point is located inside a polygon.

   B = isPointInPolygon(POINT, POLYGON)
   Returns true if the point is located within the given polygon.

   This function is simply a wrapper for the function inpolygon, to avoid
   decomposition of point and polygon coordinates.

   Example
     pt1 = [30 20];
     pt2 = [30 5];
     poly = [10 10;50 10;50 50;10 50];
     isPointInPolygon([pt1;pt2], poly)
     ans =
          1
          0

     poly = [0 0; 10 0;10 10;0 10;NaN NaN;3 3;3 7;7 7;7 3];
     pts = [5 1;5 4];
     isPointInPolygon(pts, poly);
     ans =
          1
          0


   See also
   points2d, polygons2d, inpolygon, isPointInTriangle

0001 function b = isPointInPolygon(point, poly)
0002 %ISPOINTINPOLYGON Test if a point is located inside a polygon.
0003 %
0004 %   B = isPointInPolygon(POINT, POLYGON)
0005 %   Returns true if the point is located within the given polygon.
0006 %
0007 %   This function is simply a wrapper for the function inpolygon, to avoid
0008 %   decomposition of point and polygon coordinates.
0009 %
0010 %   Example
0011 %     pt1 = [30 20];
0012 %     pt2 = [30 5];
0013 %     poly = [10 10;50 10;50 50;10 50];
0014 %     isPointInPolygon([pt1;pt2], poly)
0015 %     ans =
0016 %          1
0017 %          0
0018 %
0019 %     poly = [0 0; 10 0;10 10;0 10;NaN NaN;3 3;3 7;7 7;7 3];
0020 %     pts = [5 1;5 4];
0021 %     isPointInPolygon(pts, poly);
0022 %     ans =
0023 %          1
0024 %          0
0025 %
0026 %
0027 %   See also
0028 %   points2d, polygons2d, inpolygon, isPointInTriangle
0029 %
0030 
0031 % ------
0032 % Author: David Legland
0033 % E-mail: david.legland@inrae.fr
0034 % Created: 2009-06-19, using Matlab 7.7.0.471 (R2008b)
0035 % Copyright 2009-2024 INRA - Cepia Software Platform
0036 
0037 % In case of a multiple polygon, decompose into a set of contours, and
0038 % performs test for each contour
0039 if iscell(poly) || any(isnan(poly(:)))
0040     % transform as a cell array of simple polygons
0041     polygons = splitPolygons(poly);
0042     N = length(polygons);
0043     Np = size(point, 1);
0044     
0045     % compute orientation of polygon, and format to have Np*N matrix
0046     areas = zeros(N, 1);
0047     for i = 1:N
0048         areas(i) = polygonArea(polygons{i});
0049     end
0050     ccw = areas > 0;
0051     ccw = repmat(ccw', Np, 1);
0052     
0053     % test if point inside each polygon
0054     in = false(size(point, 1), N);
0055     for i = 1:N
0056         poly = polygons{i};
0057         in(:, i) = inpolygon(point(:,1), point(:,2), poly(:,1), poly(:,2));
0058     end
0059     
0060     % count polygons containing point, weighted by polygon orientation
0061     b = sum(in.*(ccw==1) - in.*(ccw==0), 2) > 0;
0062 
0063 else
0064     % standard test for simple polygons
0065     b = inpolygon(point(:,1), point(:,2), poly(:,1), poly(:,2));
0066 end