59 lines
2.0 KiB
JavaScript
59 lines
2.0 KiB
JavaScript
/**
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* @return {boolean} true if (lng, lat) is in bounds
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*/
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function contains(bounds, lat, lng) {
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//https://rosettacode.org/wiki/Ray-casting_algorithm
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var count = 0;
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for (var b = 0; b < bounds.length; b++) {
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var vertex1 = bounds[b];
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var vertex2 = bounds[(b + 1) % bounds.length];
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if (west(vertex1, vertex2, lng, lat))
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++count;
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}
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return count % 2;
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/**
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* @return {boolean} true if (x,y) is west of the line segment connecting A and B
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*/
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function west(A, B, x, y) {
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if (A.y <= B.y) {
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if (y <= A.y || y > B.y ||
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x >= A.x && x >= B.x) {
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return false;
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} else if (x < A.x && x < B.x) {
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return true;
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} else {
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return (y - A.y) / (x - A.x) > (B.y - A.y) / (B.x - A.x);
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}
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} else {
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return west(B, A, x, y);
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}
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}
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}
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var square = {name: 'square', bounds: [{x: 0, y: 0}, {x: 20, y: 0}, {x: 20, y: 20}, {x: 0, y: 20}]};
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var squareHole = {
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name: 'squareHole',
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bounds: [{x: 0, y: 0}, {x: 20, y: 0}, {x: 20, y: 20}, {x: 0, y: 20}, {x: 5, y: 5}, {x: 15, y: 5}, {x: 15, y: 15}, {x: 5, y: 15}]
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};
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var strange = {
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name: 'strange',
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bounds: [{x: 0, y: 0}, {x: 5, y: 5}, {x: 0, y: 20}, {x: 5, y: 15}, {x: 15, y: 15}, {x: 20, y: 20}, {x: 20, y: 0}]
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};
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var hexagon = {
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name: 'hexagon',
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bounds: [{x: 6, y: 0}, {x: 14, y: 0}, {x: 20, y: 10}, {x: 14, y: 20}, {x: 6, y: 20}, {x: 0, y: 10}]
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};
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var shapes = [square, squareHole, strange, hexagon];
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var testPoints = [{lng: 10, lat: 10}, {lng: 10, lat: 16}, {lng: -20, lat: 10},
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{lng: 0, lat: 10}, {lng: 20, lat: 10}, {lng: 16, lat: 10}, {lng: 20, lat: 20}];
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for (var s = 0; s < shapes.length; s++) {
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var shape = shapes[s];
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for (var tp = 0; tp < testPoints.length; tp++) {
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var testPoint = testPoints[tp];
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console.log(JSON.stringify(testPoint) + '\tin ' + shape.name + '\t' + contains(shape.bounds, testPoint.lat, testPoint.lng));
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}
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}
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