js 判斷一個點是否在一個多邊形之內

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出處: https://github.com/substack/point-in-polygon/blob/master/index.js

github: https://github.com/substack/point-in-polygon

module.exports = function (point, vs) {    // ray-casting algorithm based on    // http://www.ecse.rpi.edu/Homepages/wrf/Research/Short_Notes/pnpoly.html        var x = point[0], y = point[1];        var inside = false;    for (var i = 0, j = vs.length - 1; i < vs.length; j = i++) {        var xi = vs[i][0], yi = vs[i][1];        var xj = vs[j][0], yj = vs[j][1];                var intersect = ((yi > y) != (yj > y))            && (x < (xj - xi) * (y - yi) / (yj - yi) + xi);        if (intersect) inside = !inside;    }        return inside;};

//example:
var inside = require(‘point-in-polygon‘);var polygon = [ [ 1, 1 ], [ 1, 2 ], [ 2, 2 ], [ 2, 1 ] ]; //左上, 右上, 右下, 左下console.dir([    inside([ 1.5, 1.5 ], polygon),    inside([ 4.9, 1.2 ], polygon),    inside([ 1.8, 1.1 ], polygon)]);

判斷一個點是否在一個圓這內:

function pointInsideCircle(point, circle, r) {    if (r===0) return false    var dx = circle[0] - point[0]    var dy = circle[1] - point[1]    return dx * dx + dy * dy <= r * r}

 

js 判斷一個點是否在一個多邊形之內