ashatora/openlayers
1
0
Fork 0
Code Issues Pull Requests Projects Releases Wiki Activity

Add ol.geom.flat.linearRingArea

Browse Source
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
Download Patch File Download Diff File Expand all files Collapse all files

22
src/ol/geom/flatgeom.js
View File

@@ -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.

14
test/spec/ol/geom/flatgeom.test.js
View File

@@ -127,6 +127,20 @@ describe('ol.geom.flat', function() {
});
describe('ol.geom.flat.linearRingArea', function() {
it('calcaultes the area of a triangle', function() {
var area = ol.geom.flat.linearRingArea([0, 0, 0.5, 1, 1, 0], 0, 6, 2);
expect(area).to.be(0.5);
});
it('calculates the area of a unit square', function() {
var area = ol.geom.flat.linearRingArea([0, 0, 0, 1, 1, 1, 1, 0], 0, 8, 2);
expect(area).to.be(1);
});
});
describe('ol.geom.flat.linearRingIsClockwise', function() {
it('identifies clockwise rings', function() {