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Merge pull request #361 from sdikiy/patch-1

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accurate calculation of the centroid for small objects with large coordinates (p=sdikiy,r=marcjansen,sbrunner)
This commit is contained in:
Marc Jansen
2012-04-03 11:58:57 -07:00
parent 96e5241507 0460bd2ae8
commit 326598a75c
2 changed files with 35 additions and 12 deletions
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27
lib/OpenLayers/Geometry/LinearRing.js
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@@ -198,15 +198,26 @@ OpenLayers.Geometry.LinearRing = OpenLayers.Class(
} else if (len > 2) {
var sumX = 0.0;
var sumY = 0.0;
for (var i = 0; i < this.components.length - 1; i++) {
var b = this.components[i];
var c = this.components[i+1];
sumX += (b.x + c.x) * (b.x * c.y - c.x * b.y);
sumY += (b.y + c.y) * (b.x * c.y - c.x * b.y);
}
var x0 = this.components[0].x;
var y0 = this.components[0].y;
var area = -1 * this.getArea();
var x = sumX / (6 * area);
var y = sumY / (6 * area);
if (area != 0) {
for (var i = 0; i < len - 1; i++) {
var b = this.components[i];
var c = this.components[i+1];
sumX += (b.x + c.x - 2 * x0) * ((b.x - x0) * (c.y - y0) - (c.x - x0) * (b.y - y0));
sumY += (b.y + c.y - 2 * y0) * ((b.x - x0) * (c.y - y0) - (c.x - x0) * (b.y - y0));
}
var x = x0 + sumX / (6 * area);
var y = y0 + sumY / (6 * area);
} else {
for (var i = 0; i < len - 1; i++) {
sumX += this.components[i].x;
sumY += this.components[i].y;
}
var x = sumX / (len - 1);
var y = sumY / (len - 1);
}
return new OpenLayers.Geometry.Point(x, y);
} else {
return null;