面是否包含點的算法

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;
}

來自爲知筆記(Wiz)