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Add ol.geom.flat.linearRingArea

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This commit is contained in:
Tom Payne
2013-12-02 12:05:04 +01:00
parent c3378d0bd5
commit f80cad531b
2 changed files with 36 additions and 0 deletions
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22
src/ol/geom/flatgeom.js
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@@ -257,6 +257,28 @@ ol.geom.flat.lineStringLength = function(flatCoordinates, offset, end, stride) {
};
/**
* @param {Array.<number>} flatCoordinates Flat coordinates.
* @param {number} offset Offset.
* @param {number} end End.
* @param {number} stride Stride.
* @return {number} Area.
*/
ol.geom.flat.linearRingArea = function(flatCoordinates, offset, end, stride) {
var twiceArea = 0;
var x1 = flatCoordinates[end - stride];
var y1 = flatCoordinates[end - stride + 1];
for (; offset < end; offset += stride) {
var x2 = flatCoordinates[offset];
var y2 = flatCoordinates[offset + 1];
twiceArea += x1 * y2 - y1 * x2;
x1 = x2;
y1 = y2;
}
return Math.abs(twiceArea / 2);
};
/**
* @param {Array.<number>} flatCoordinates Flat coordinates.
* @param {number} offset Offset.