65 lines
1.7 KiB
JavaScript
65 lines
1.7 KiB
JavaScript
goog.provide('ol.geom.flat.area');
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/**
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* @param {Array.<number>} flatCoordinates Flat coordinates.
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* @param {number} offset Offset.
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* @param {number} end End.
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* @param {number} stride Stride.
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* @return {number} Area.
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*/
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ol.geom.flat.area.linearRing = function(flatCoordinates, offset, end, stride) {
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var twiceArea = 0;
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var x1 = flatCoordinates[end - stride];
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var y1 = flatCoordinates[end - stride + 1];
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for (; offset < end; offset += stride) {
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var x2 = flatCoordinates[offset];
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var y2 = flatCoordinates[offset + 1];
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twiceArea += y1 * x2 - x1 * y2;
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x1 = x2;
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y1 = y2;
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}
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return twiceArea / 2;
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};
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/**
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* @param {Array.<number>} flatCoordinates Flat coordinates.
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* @param {number} offset Offset.
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* @param {Array.<number>} ends Ends.
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* @param {number} stride Stride.
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* @return {number} Area.
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*/
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ol.geom.flat.area.linearRings =
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function(flatCoordinates, offset, ends, stride) {
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var area = 0;
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var i, ii;
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for (i = 0, ii = ends.length; i < ii; ++i) {
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var end = ends[i];
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area += ol.geom.flat.area.linearRing(flatCoordinates, offset, end, stride);
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offset = end;
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}
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return area;
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};
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/**
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* @param {Array.<number>} flatCoordinates Flat coordinates.
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* @param {number} offset Offset.
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* @param {Array.<Array.<number>>} endss Endss.
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* @param {number} stride Stride.
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* @return {number} Area.
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*/
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ol.geom.flat.area.linearRingss =
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function(flatCoordinates, offset, endss, stride) {
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var area = 0;
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var i, ii;
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for (i = 0, ii = endss.length; i < ii; ++i) {
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var ends = endss[i];
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area +=
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ol.geom.flat.area.linearRings(flatCoordinates, offset, ends, stride);
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offset = ends[ends.length - 1];
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}
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return area;
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};
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