js判斷點在某多邊形閉合區域內

判斷某點在閉合的多邊形區域內，可使用該方法判斷

 

    isInPolygon(checkPoint, polygonPoints) {
      var counter = 0;
      var i;
      var xinters;
      var p1, p2;
      var pointCount = polygonPoints.length;
      p1 = polygonPoints[0];

      for (i = 1; i <= pointCount; i++) {
        p2 = polygonPoints[i % pointCount];
        if (
          checkPoint[0] > Math.min(p1[0], p2[0]) &&
          checkPoint[0] <= Math.max(p1[0], p2[0])
        ) {
          if (checkPoint[1] <= Math.max(p1[1], p2[1])) {
            if (p1[0] != p2[0]) {
              xinters =
                ((checkPoint[0] - p1[0]) * (p2[1] - p1[1])) / (p2[0] - p1[0]) +
                p1[1];
              if (p1[1] == p2[1] || checkPoint[1] <= xinters) {
                counter++;
              }
            }
          }
        }
        p1 = p2;
      }
      if (counter % 2 == 0) {
        return false;
      } else {
        return true;
      }
    }

 

注意：

checkPoint的數據形式是一維數組

[591, 280]

 

polygonPoints的數據形式是二位數組

[Array(2), Array(2), Array(2), Array(2), Array(2), Array(2)]

 

打印兩個數據格式如圖