面是否包含点的算法

from arcgis Javascript api：

 

function polygonContainPoint(pt,polygon) {
    var rings = polygon.rings,
        ring, bresult = false,
        pt1, pt2, ringlength, j, i, indexrings, ringslength = rings.length;
    for (indexrings = 0; indexrings < ringslength; indexrings++) {
        ring = rings[indexrings];
        ringlength = ring.length;
        j = 0;
        for (i = 0; i < ringlength; i++) {
            j++;
            if (j === ringlength) {
                j = 0;
            }
            pt1 = ring[i];
            pt2 = ring[j];
            if ((pt1[1] < pt.y && pt2[1] >= pt.y || pt2[1] < pt.y && pt1[1] >= pt.y) && (pt1[0] + (pt.y - pt1[1]) / (pt2[1] - pt1[1]) * (pt2[0] - pt1[0]) < pt.x)) {
                bresult = !bresult;
            }
        }
    }
    return bresult;
}

来自为知笔记(Wiz)