百度地图API画多边型，测面积
效果：
脚本：
耕地分布图
GeoUtils.js
/**
* @fileoverview GeoUtils类提供若干几何算法，用来帮助用户判断点与矩形、
* 圆形、多边形线、多边形面的关系,并提供计算折线长度和多边形的面积的公式。
* 主入口类是GeoUtils，
* 基于Baidu Map API 1.2。
*
* @author Baidu Map Api Group
* @version 1.2
*/
//BMapLib.GeoUtils.degreeToRad(Number)
//将度转化为弧度
//BMapLib.GeoUtils.getDistance(Point, Point)
//计算两点之间的距离,两点坐标必须为经纬度
//BMapLib.GeoUtils.getPolygonArea(polygon)
//计算多边形面或点数组构建图形的面积,注意：坐标类型只能是经纬度，且不适合计算自相交多边形的面积(封闭的面积)
//BMapLib.GeoUtils.getPolylineDistance(polyline)
//计算折线或者点数组的长度
//BMapLib.GeoUtils.isPointInCircle(point, circle)
//判断点是否在圆形内
//BMapLib.GeoUtils.isPointInPolygon(point, polygon)
//判断点是否多边形内
//BMapLib.GeoUtils.isPointInRect(point, bounds)
//判断点是否在矩形内
//BMapLib.GeoUtils.isPointOnPolyline(point, polyline)
//判断点是否在折线上
//BMapLib.GeoUtils.radToDegree(Number)
//将弧度转化为度
/**
* @namespace BMap的所有library类均放在BMapLib命名空间下
*/
var BMapLib = window.BMapLib = BMapLib || {};
(function () {
/**
* 地球半径
*/
var EARTHRADIUS = 6370996.81;
/**
* @exports GeoUtils as BMapLib.GeoUtils
*/
var GeoUtils =
/**
* GeoUtils类，静态类，勿需实例化即可使用
* @class GeoUtils类的入口。
* 该类提供的都是静态方法，勿需实例化即可使用。
*/
BMapLib.GeoUtils = function () {
}
/**
* 判断点是否在矩形内
* @param {Point} point 点对象
* @param {Bounds} bounds 矩形边界对象
* @returns {Boolean} 点在矩形内返回true,否则返回false
*/
GeoUtils.isPointInRect = function (point, bounds) {
//检查类型是否正确
if (!(point instanceof BMap.Point) ||
!(bounds instanceof BMap.Bounds)) {
return false;
}
var sw = bounds.getSouthWest(); //西南脚点
var ne = bounds.getNorthEast(); //东北脚点
return (point.lng >= sw.lng && point.lng <= ne.lng && point.lat >= sw.lat && point.lat <= ne.lat);
}
/**
* 判断点是否在圆形内
* @param {Point} point 点对象
* @param {Circle} circle 圆形对象
* @returns {Boolean} 点在圆形内返回true,否则返回false
*/
GeoUtils.isPointInCircle = function (point, circle) {
//检查类型是否正确
if (!(point instanceof BMap.Point) ||
!(circle instanceof BMap.Circle)) {
return false;
}
//point与圆心距离小于圆形半径，则点在圆内，否则在圆外
var c = circle.getCenter();
var r = circle.getRadius();
var dis = GeoUtils.getDistance(point, c);
if (dis <= r) {
return true;
} else {
return false;
}
}
/**
* 判断点是否在折线上
* @param {Point} point 点对象
* @param {Polyline} polyline 折线对象
* @returns {Boolean} 点在折线上返回true,否则返回false
*/
GeoUtils.isPointOnPolyline = function (point, polyline) {
//检查类型
if (!(point instanceof BMap.Point) ||
!(polyline instanceof BMap.Polyline)) {
return false;
}
//首先判断点是否在线的外包矩形内，如果在，则进一步判断，否则返回false
var lineBounds = polyline.getBounds();
if (!this.isPointInRect(point, lineBounds)) {
return false;
}
//判断点是否在线段上，设点为Q，线段为P1P2 ，
//判断点Q在该线段上的依据是：( Q - P1 ) × ( P2 - P1 ) = 0，且 Q 在以 P1，P2为对角顶点的矩形内
var pts = polyline.getPath();
for (var i = 0; i < pts.length - 1; i++) {
var curPt = pts[i];
var nextPt = pts[i + 1];
//首先判断point是否在curPt和nextPt之间，即：此判断该点是否在该线段的外包矩形内
if (point.lng >= Math.min(curPt.lng, nextPt.lng) && point.lng <= Math.max(curPt.lng, nextPt.lng) &&
point.lat >= Math.min(curPt.lat, nextPt.lat) && point.lat <= Math.max(curPt.lat, nextPt.lat)) {
//判断点是否在直线上公式
var precision = (curPt.lng - point.lng) * (nextPt.lat - point.lat) - (nextPt.lng - point.lng) * (curPt.lat - point.lat);
if (precision < 2e-10 && precision > -2e-10) {//实质判断是否接近0
return true;
}
}
}
return false;
}
/**
* 判断点是否多边形内
* @param {Point} point 点对象
* @param {Polyline} polygon 多边形对象
* @returns {Boolean} 点在多边形内返回true,否则返回false
*/
GeoUtils.isPointInPolygon = function (point, polygon) {
//检查类型
if (!(point instanceof BMap.Point) ||
!(polygon instanceof BMap.Polygon)) {
return false;
}
//首先判断点是否在多边形的外包矩形内，如果在，则进一步判断，否则返回false
var polygonBounds = polygon.getBounds();
if (!this.isPointInRect(point, polygonBounds)) {
return false;
}
var pts = polygon.getPath(); //获取多边形点
//下述代码来源：http://paulbourke.net/geometry/insidepoly/，进行了部分修改
//基本思想是利用射线法，计算射线与多边形各边的交点，如果是偶数，则点在多边形外，否则
//在多边形内。还会考虑一些特殊情况，如点在多边形顶点上，点在多边形边上等特殊情况。
var N = pts.length;
var boundOrVertex = true; //如果点位于多边形的顶点或边上，也算做点在多边形内，直接返回true
var intersectCount = 0; //cross points count of x
var precision = 2e-10; //浮点类型计算时候与0比较时候的容差
var p1, p2; //neighbour bound vertices
var p = point; //测试点
p1 = pts[0]; //left vertex
for (var i = 1; i <= N; ++i) {//check all rays
if (p.equals(p1)) {
return boundOrVertex; //p is an vertex
}
p2 = pts[i % N]; //right vertex
if (p.lat < Math.min(p1.lat, p2.lat) || p.lat > Math.max(p1.lat, p2.lat)) {//ray is outside of our interests
p1 = p2;
continue; //next ray left point
}
if (p.lat > Math.min(p1.lat, p2.lat) && p.lat < Math.max(p1.lat, p2.lat)) {//ray is crossing over by the algorithm (common part of)
if (p.lng <= Math.max(p1.lng, p2.lng)) {//x is before of ray
if (p1.lat == p2.lat && p.lng >= Math.min(p1.lng, p2.lng)) {//overlies on a horizontal ray
return boundOrVertex;
}
if (p1.lng == p2.lng) {//ray is vertical
if (p1.lng == p.lng) {//overlies on a vertical ray
return boundOrVertex;
} else {//before ray
++intersectCount;
}
} else {//cross point on the left side
var xinters = (p.lat - p1.lat) * (p2.lng - p1.lng) / (p2.lat - p1.lat) + p1.lng; //cross point of lng
if (Math.abs(p.lng - xinters) < precision) {//overlies on a ray
return boundOrVertex;
}
if (p.lng < xinters) {//before ray
++intersectCount;
}
}
}
} else {//special case when ray is crossing through the vertex
if (p.lat == p2.lat && p.lng <= p2.lng) {//p crossing over p2
var p3 = pts[(i + 1) % N]; //next vertex
if (p.lat >= Math.min(p1.lat, p3.lat) && p.lat <= Math.max(p1.lat, p3.lat)) {//p.lat lies between p1.lat & p3.lat
++intersectCount;
} else {
intersectCount += 2;
}
}
}
p1 = p2; //next ray left point
}
if (intersectCount % 2 == 0) {//偶数在多边形外
return false;
} else { //奇数在多边形内
return true;
}
}
/**
* 将度转化为弧度
* @param {degree} Number 度
* @returns {Number} 弧度
*/
GeoUtils.degreeToRad = function (degree) {
return Math.PI * degree / 180;
}
/**
* 将弧度转化为度
* @param {radian} Number 弧度
* @returns {Number} 度
*/
GeoUtils.radToDegree = function (rad) {
return (180 * rad) / Math.PI;
}
/**
* 将v值限定在a,b之间，纬度使用
*/
function _getRange(v, a, b) {
if (a != null) {
v = Math.max(v, a);
}
if (b != null) {
v = Math.min(v, b);
}
return v;
}
/**
* 将v值限定在a,b之间，经度使用
*/
function _getLoop(v, a, b) {
while (v > b) {
v -= b - a
}
while (v < a) {
v += b - a
}
return v;
}
/**
* 计算两点之间的距离,两点坐标必须为经纬度
* @param {point1} Point 点对象
* @param {point2} Point 点对象
* @returns {Number} 两点之间距离，单位为米
*/
GeoUtils.getDistance = function (point1, point2) {
//判断类型
if (!(point1 instanceof BMap.Point) ||
!(point2 instanceof BMap.Point)) {
return 0;
}
point1.lng = _getLoop(point1.lng, -180, 180);
point1.lat = _getRange(point1.lat, -74, 74);
point2.lng = _getLoop(point2.lng, -180, 180);
point2.lat = _getRange(point2.lat, -74, 74);
var x1, x2, y1, y2;
x1 = GeoUtils.degreeToRad(point1.lng);
y1 = GeoUtils.degreeToRad(point1.lat);
x2 = GeoUtils.degreeToRad(point2.lng);
y2 = GeoUtils.degreeToRad(point2.lat);
return EARTHRADIUS * Math.acos((Math.sin(y1) * Math.sin(y2) + Math.cos(y1) * Math.cos(y2) * Math.cos(x2 - x1)));
}
/**
* 计算折线或者点数组的长度
* @param {Polyline|Array} polyline 折线对象或者点数组
* @returns {Number} 折线或点数组对应的长度
*/
GeoUtils.getPolylineDistance = function (polyline) {
//检查类型
if (polyline instanceof BMap.Polyline ||
polyline instanceof Array) {
//将polyline统一为数组
var pts;
if (polyline instanceof BMap.Polyline) {
pts = polyline.getPath();
} else {
pts = polyline;
}
if (pts.length < 2) {//小于2个点，返回0
return 0;
}
//遍历所有线段将其相加，计算整条线段的长度
var totalDis = 0;
for (var i = 0; i < pts.length - 1; i++) {
var curPt = pts[i];
var nextPt = pts[i + 1]
var dis = GeoUtils.getDistance(curPt, nextPt);
totalDis += dis;
}
return totalDis;
} else {
return 0;
}
}
/**
* 计算多边形面或点数组构建图形的面积,注意：坐标类型只能是经纬
度，且不适合计算自相交多边形的面积
* @param {Polygon|Array} polygon 多边形面对象或者点数
组
* @returns {Number} 多边形面或点数组构成图形的面积
*/
GeoUtils.getPolygonArea = function (polygon) {
//检查类型
if (!(polygon instanceof BMap.Polygon) &&
!(polygon instanceof Array)) {
return 0;
}
var pts;
if (polygon instanceof BMap.Polygon) {
pts = polygon.getPath();
} else {
pts = polygon;
}
if (pts.length < 3) {//小于3个顶点，不能构建面
return 0;
}
var totalArea = 0; //初始化总面积
var LowX = 0.0;
var LowY = 0.0;
var MiddleX = 0.0;
var MiddleY = 0.0;
var HighX = 0.0;
var HighY = 0.0;
var AM = 0.0;
var BM = 0.0;
var CM = 0.0;
var AL = 0.0;
var BL = 0.0;
var CL = 0.0;
var AH = 0.0;
var BH = 0.0;
var CH = 0.0;
var CoefficientL = 0.0;
var CoefficientH = 0.0;
var ALtangent = 0.0;
var BLtangent = 0.0;
var CLtangent = 0.0;
var AHtangent = 0.0;
var BHtangent = 0.0;
var CHtangent = 0.0;
var ANormalLine = 0.0;
var BNormalLine = 0.0;
var CNormalLine = 0.0;
var OrientationValue = 0.0;
var AngleCos = 0.0;
var Sum1 = 0.0;
var Sum2 = 0.0;
var Count2 = 0;
var Count1 = 0;
var Sum = 0.0;
var Radius = EARTHRADIUS; //6378137.0,WGS84椭球半径
var Count = pts.length;
for (var i = 0; i < Count; i++) {
if (i == 0) {
LowX = pts[Count - 1].lng * Math.PI / 180;
LowY = pts[Count - 1].lat * Math.PI / 180;
MiddleX = pts[0].lng * Math.PI / 180;
MiddleY = pts[0].lat * Math.PI / 180;
HighX = pts[1].lng * Math.PI / 180;
HighY = pts[1].lat * Math.PI / 180;
}
else if (i == Count - 1) {
LowX = pts[Count - 2].lng * Math.PI / 180;
LowY = pts[Count - 2].lat * Math.PI / 180;
MiddleX = pts[Count - 1].lng * Math.PI / 180;
MiddleY = pts[Count - 1].lat * Math.PI / 180;
HighX = pts[0].lng * Math.PI / 180;
HighY = pts[0].lat * Math.PI / 180;
}
else {
LowX = pts[i - 1].lng * Math.PI / 180;
LowY = pts[i - 1].lat * Math.PI / 180;
MiddleX = pts[i].lng * Math.PI / 180;
MiddleY = pts[i].lat * Math.PI / 180;
HighX = pts[i + 1].lng * Math.PI / 180;
HighY = pts[i + 1].lat * Math.PI / 180;
}
AM = Math.cos(MiddleY) * Math.cos(MiddleX);
BM = Math.cos(MiddleY) * Math.sin(MiddleX);
CM = Math.sin(MiddleY);
AL = Math.cos(LowY) * Math.cos(LowX);
BL = Math.cos(LowY) * Math.sin(LowX);
CL = Math.sin(LowY);
AH = Math.cos(HighY) * Math.cos(HighX);
BH = Math.cos(HighY) * Math.sin(HighX);
CH = Math.sin(HighY);
CoefficientL = (AM * AM + BM * BM + CM * CM) / (AM * AL + BM * BL + CM * CL);
CoefficientH = (AM * AM + BM * BM + CM * CM) / (AM * AH + BM * BH + CM * CH);
ALtangent = CoefficientL * AL - AM;
BLtangent = CoefficientL * BL - BM;
CLtangent = CoefficientL * CL - CM;
AHtangent = CoefficientH * AH - AM;
BHtangent = CoefficientH * BH - BM;
CHtangent = CoefficientH * CH - CM;
AngleCos = (AHtangent * ALtangent + BHtangent * BLtangent + CHtangent * CLtangent) / (Math.sqrt(AHtangent * AHtangent + BHtangent * BHtangent + CHtangent * CHtangent) * Math.sqrt(ALtangent * ALtangent + BLtangent * BLtangent + CLtangent * CLtangent));
AngleCos = Math.acos(AngleCos);
ANormalLine = BHtangent * CLtangent - CHtangent * BLtangent;
BNormalLine = 0 - (AHtangent * CLtangent - CHtangent * ALtangent);
CNormalLine = AHtangent * BLtangent - BHtangent * ALtangent;
if (AM != 0)
OrientationValue = ANormalLine / AM;
else if (BM != 0)
OrientationValue = BNormalLine / BM;
else
OrientationValue = CNormalLine / CM;
if (OrientationValue > 0) {
Sum1 += AngleCos;
Count1++;
}
else {
Sum2 += AngleCos;
Count2++;
}
}
var tempSum1, tempSum2;
tempSum1 = Sum1 + (2 * Math.PI * Count2 - Sum2);
tempSum2 = (2 * Math.PI * Count1 - Sum1) + Sum2;
if (Sum1 > Sum2) {
if ((tempSum1 - (Count - 2) * Math.PI) < 1)
Sum = tempSum1;
else
Sum = tempSum2;
}
else {
if ((tempSum2 - (Count - 2) * Math.PI) < 1)
Sum = tempSum2;
else
Sum = tempSum1;
}
totalArea = (Sum - (Count - 2) * Math.PI) * Radius * Radius;
return totalArea; //返回总面积
}
})(); //闭包结束 注意：
BMapLib.GeoUtils.getPolygonArea(polygon) 不适合计算自相交多边形的面积(封闭的面积)
转自:http://blog.csdn.net/litao2/article/details/9836419