Hello,

I have a polygon created from an SVG file ( you can find this file here).

I want to test if random points are inside this polygon or not. I am using the java.awt.Polygon class as described on the wiki.

However the contains method returns true only if a point is exactly on the border rather than if it's simply inside the polygon. Should I use another method, algorithm or could it come from an error in the polygon definition ? Maybe it has too many points ? (replacing the drawing trough the Polygon class by beginShape()-endShape() sequence leaves the polygon unfilled too).

Thank you in advance.

1. /**
2.  program to try inclusion test (java.awt.Polygon) of random points in complex polygon
3. */
4. //Library import
5. import geomerative.*;
6. import java.awt.Polygon; //required ?
7. //Defines variables
8. RShape s;
9. RShape polyshp;
10. RPoint[] points;
11. int [][] coords;
12. float minX;
13. float minY;
14. float maxX;
15. float maxY;
16. Poly p;
17. void setup() {
18.   //style
19.   RG.init(this);
20.   RG.ignoreStyles(true);
21.   smooth();
22.   g.smooth = true;
23.   rectMode(CENTER);
24.   background(192);
25.   frameRate(120);
26.   shapeMode(CORNER);
27.   ellipseMode(CENTER);
28.   //load svg
29.   s = RG.loadShape("BelgiumC.svg");
30.   points = s.getPoints();
31.   println("points.length : "+points.length);
32.   coords = new int[2][points.length] ;
33.   // translate points into 2D array
34.   for (int i = 0; i < points.length ; i++) {
35.     coords[0][i] = round(points[i].x / 2);
36.     coords[1][i] = round(points[i].y / 2);
37.   }
38.   //defines polygon with points
39.   p=new Poly(coords[0],coords[1],points.length);
40.   //finds minima and maxima in svg
41.   minX = min(coords[0]);
42.   maxX = max(coords[0]);
43.   minY = min(coords[1]);
44.   maxY = max(coords[1]); 
45.   //sizes window according to svg coordinates
46.   size(int((maxX-minX))+50, int((maxY-minY))+50, JAVA2D);
47. }
48. void draw() {
49.   //settings to draw shape
50.   strokeWeight(1);
51.   fill(0, 128, 255, 255); //doesn't work
52.   stroke(0, 0, 0);
53.   //draws shape
54.   p.drawMe(); 
55. }
56. //click to create random point and draw ellipse if within polygon
57. void mousePressed() { 
58.   //chooses a random point and draws if it is included in shape
59.     // random coordinates
60.     int aleaX = int(random(0, width));
61.     int aleaY = int(random(0, height));
62.     if (p.contains(aleaX, aleaY)) {  
63.       println("p.contains = "+p.contains(aleaX, aleaY));
64.       fill(255, 255, 0);
65.       stroke(0, 128, 255);
66.       strokeWeight(2);
67.       ellipse(aleaX, aleaY, 20, 20);
68.     }    else {
69.       println("p.contains = "+p.contains(aleaX, aleaY));
70.     }
71. }
72. //ADDITIONAL CLASSES
73. //class to draw and test polygon
74. class Poly extends java.awt.Polygon{
75.   public Poly(int[] x,int[] y, int n){
76.     //call the java.awt.Polygon constructor
77.     super(x,y,n);
78.   }
79.   void drawMe(){
80.     beginShape();
81.     for(int i=0;i<npoints;i++){
82.       vertex(xpoints[i],ypoints[i]);
83.     }
84.     endShape();
85.   }
86. }