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Add polygonCentroid and polygon area to utils

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Ansis Brammanis
2013-01-20 22:21:18 -05:00
parent 0afb564435
commit 572c111bf1
1 changed files with 24 additions and 0 deletions
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js/id/util.js
+24
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@@ -145,3 +145,27 @@ iD.util.geo.polygonIntersectsPolygon = function(outer, inner) {
return iD.util.geo.pointInPolygon(point, outer);
});
};
// May have issues with self interesecting polygons
iD.util.geo.polygonCentroid = function(polygon) {
var x = 0,
y = 0,
area = iD.util.geo.area(polygon);
for (var i = 0, j = polygon.length - 1; i < polygon.length; j = i++) {
var xi = polygon[i][0], yi = polygon[i][1];
var xj = polygon[j][0], yj = polygon[j][1];
x += (xi + xj) * (xj * yi - xi * yj);
y += (yi + yj) * (xj * yi - xi * yj);
}
return [x / 6 / area, y / 6 / area];
};
iD.util.geo.area = function(polygon) {
var area = 0;
for (var i = 0, j = polygon.length - 1; i < polygon.length; j = i++) {
var xi = polygon[i][0], yi = polygon[i][1];
var xj = polygon[j][0], yj = polygon[j][1];
area += xj * yi - xi * yj;
}
return area/2;
};