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accurate calculation of the centroid for small objects with large coordinates

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sdikiy
2012-03-27 16:12:31 +03:00
parent d1d5ab9930
commit 8c93d477ba
1 changed files with 13 additions and 5 deletions
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18
lib/OpenLayers/Geometry/LinearRing.js
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@@ -198,15 +198,23 @@ 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 averX = 0.0;
var averY = 0.0;
for (var i = 0; i < len; i++) {
averX += this.components[i].x;
averY += this.components[i].y;
}
averX = averX / len;
averY = averY / len;
for (var i = 0; i < len - 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);
sumX += (b.x + c.x - 2 * averX) * ((b.x - averX) * (c.y - averY) - (c.x - averX) * (b.y - averY));
sumY += (b.y + c.y - 2 * averY) * ((b.x - averX) * (c.y - averY) - (c.x - averX) * (b.y - averY));
}
var area = -1 * this.getArea();
var x = sumX / (6 * area);
var y = sumY / (6 * area);
var x = averX + sumX / (6 * area);
var y = averY + sumY / (6 * area);
return new OpenLayers.Geometry.Point(x, y);
} else {
return null;