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你可以用添加/删除覆盖物这个API试试
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// 百度地图API功能
var map = new BMap.Map("allmap");
var point = new BMap.Point(116.404, 39.915);
map.centerAndZoom(point, 15);
var marker = new BMap.Marker(new BMap.Point(116.404, 39.915)); // 创建点
var polyline = new BMap.Polyline([
new BMap.Point(116.399, 39.910),
new BMap.Point(116.405, 39.920),
new BMap.Point(116.425, 39.900)
], {strokeColor:"blue", strokeWeight:2, strokeOpacity:0.5}); //创建折线
var circle = new BMap.Circle(point,500,{strokeColor:"blue", strokeWeight:2, strokeOpacity:0.5}); //创建圆
var polygon = new BMap.Polygon([
new BMap.Point(116.387112,39.920977),
new BMap.Point(116.385243,39.913063),
new BMap.Point(116.394226,39.917988),
new BMap.Point(116.401772,39.921364),
new BMap.Point(116.41248,39.927893)
], {strokeColor:"blue", strokeWeight:2, strokeOpacity:0.5}); //创建多边形
var pStart = new BMap.Point(116.392214,39.918985);
var pEnd = new BMap.Point(116.41478,39.911901);
var rectangle = new BMap.Polygon([
new BMap.Point(pStart.lng,pStart.lat),
new BMap.Point(pEnd.lng,pStart.lat),
new BMap.Point(pEnd.lng,pEnd.lat),
new BMap.Point(pStart.lng,pEnd.lat)
], {strokeColor:"blue", strokeWeight:2, strokeOpacity:0.5}); //创建矩形
//添加覆盖物
function add_overlay(){
map.addOverlay(marker); //增加点
map.addOverlay(polyline); //增加折线
map.addOverlay(circle); //增加圆
map.addOverlay(polygon); //增加多边形
map.addOverlay(rectangle); //增加矩形
}
//清除覆盖物
function remove_overlay(){
map.clearOverlays();
}
不过这需要三角函数，关于三角函数可以去看一下《揭秘javascript的三角函数》这篇文章，那里面对三角函数讲得很清楚了。
参考资料：
《揭秘javascript的三角函数》来自：
纯js不好实现,但是配合html,css就有了近似的办法.下面提供一个解决方案,已知两个点的坐标,为它们画一条带箭头的弧线.
html
head
meta http-equiv = "content-type" content = "text/html; charset = gb2312"
title箭头弧线/title
style type = "text/css"
span { position: absolute; width: 5px; height: 5px; background-color: #0000ff; display: block; border-radius: 50%; }
/style
script language = "javascript"
function locateO () {
var x0 = parseInt (spnA.style.left, 10), y0 = parseInt (spnA.style.top, 10), x1 = parseInt (spnB.style.left, 10), y1 = parseInt (spnB.style.top, 10), horizontalDistance = Math.abs (x1 - x0), verticalDistance = Math.abs (y1 - y0), x = Math.min (x0, x1) + horizontalDistance / 2, y = Math.min (y0, y1) + verticalDistance / 2, distance = Math.sqrt (Math.pow (horizontalDistance, 2) + Math.pow (verticalDistance, 2)), array = new Array (x0, y0, x1, y1, distance);
spnO.style.left = x;
spnO.style.top = y;
return array;
}
function getRadian (x0, y0, x1, y1) {
var horizontalDistance = Math.abs (x1 - x0), verticalDistance = Math.abs (y1 - y0), rate = horizontalDistance == 0 ? 0 : verticalDistance / horizontalDistance, radian;
if (y1 y0) {
if (x1 x0) {
radian = - Math.atan (rate);
} else if (x1 == x0) {
radian = - Math.PI / 2;
} else {
radian = - (Math.PI - Math.atan (rate));
}
} else if (y1 == y0) {
radian = x1 left ? 0 : - Math.PI;
} else if (x1 x0) {
radian = - (Math.PI + Math.atan (rate));
} else if (x1 == x0) {
radian = - Math.PI * 3 / 2;
} else {
radian = - 2 * Math.PI + Math.atan (rate);
}
return radian;
}
function getAngle (radian) {
var angle = - radian * 180 / Math.PI;
return angle;
}
function slantArc (x0, y0, x1, y1) {
var radian = getRadian (x0, y0, x1, y1), angle = 360 - getAngle (radian);
cnvArc.style.transform = "rotate(" + angle + "deg)";
}
function drawArc (x0, y0, width) {
var context = cnvArc.getContext ("2d"), radius = width / 2, height = radius / 2;
cnvArc.width = width + 10;
cnvArc.height = height;
cnvArc.style.left = x0;
cnvArc.style.top = y0 - height;
context.ellipse (radius + 5, height, radius, height / 2, 0, 0, Math.PI * 2);
context.strokeStyle = "#00ff00";
context.stroke ();
}
function hex (figure) {
return figure.toString (16);
}
function zeroize (cluster) {
if (cluster.length 2) {
cluster = 0 + cluster;
}
return cluster;
}
function getColour (red, green, blue) {
return "#" + zeroize (hex (red)) + zeroize (hex (green)) + zeroize (hex (blue));
}
function printArc () {
var width = cnvArc.width, height = cnvArc.height, context = cnvArc.getContext ("2d"), imageData = context.getImageData (0, 0, width, height), data = imageData.data, coordinates = new Array (), cluster = "", i, red, green, blue, colour, index, x, y;
for (i = 0; i data.length; i += 4) {
red = data [i];
green = data [i + 1];
blue = data [i + 2];
colour = getColour (red, green, blue);
index = i / 4;
y = parseInt (index / width, 10);
x = index % width;
if (x == 0) {
//console.log (y + "\n" + cluster);
cluster = "";
}
cluster += x + ":" + colour + " ";
if (colour == "#00ff00") {
coordinates.push (new Array (x, y));
}
}
return coordinates;
}
function sortCoordinates (coordinates, direction) {
var i = 0, flag, j, coordinate;
do {
flag = false;
for (j = 0; j coordinates.length - 1 - i; j ++) {
if (direction (coordinates [j] [0] coordinates [j + 1] [0] || coordinates [j] [0] == coordinates [j + 1] [0] coordinates [j] [1] coordinates [j + 1] [1]) || ! direction (coordinates [j] [0] coordinates [j + 1] [0] || coordinates [j] [0] == coordinates [j + 1] [0] coordinates [j] [1] coordinates [j + 1] [1])) {
coordinate = coordinates [j];
coordinates [j] = coordinates [j + 1];
coordinates [j + 1] = coordinate;
flag = true;
}
}
i ++;
} while (flag);
}
function drawArrow (x0, y0, x1, y1) {
var context = cnvArc.getContext ("2d"), colour = "#00ff00", angle = (x1 - x0) / (y1 - y0);
context.strokeStyle = colour;
context.fillStyle = colour;
context.setLineDash ([3, 3]);
context.beginPath ();
context.arc (x0, y0, 1, 0, 2 * Math.PI);
context.translate (0, 0, 0);
context.moveTo (x0, y0);
context.lineTo (x1, y1);
context.fill ();
context.stroke ();
context.save ();
context.translate (x1, y1);
angle = Math.atan (angle);
context.rotate ((y1 = y0 ? 0 : Math.PI) - angle);
context.lineTo (- 3, - 9);
context.lineTo (0, - 3);
context.lineTo (3, - 9);
context.lineTo (0, 0);
context.fill ();
context.restore ();
context.closePath ();
}
function initialize () {
var array = locateO (), x0 = array [0], y0 = array [1], x1 = array [2], y1 = array [3], width = array [4], direction = x1 x0, coordinates, length, coordinate0, coordinate1, x2, y2, x3, y3;
drawArc (x0, y0, width);
coordinates = printArc ();
length = coordinates.length;
sortCoordinates (coordinates, direction);
coordinate0 = coordinates [length - 2];
x2 = coordinate0 [0];
y2 = coordinate0 [1];
coordinate1 = coordinates [length - 1];
x3 = coordinate1 [0];
y3 = coordinate1 [1];
drawArrow (x2, y2, x3, y3);
slantArc (x0, y0, x1, y1);
}
/script
/head
body style = "margin: 0;" onload = "initialize ()"
span id = "spnA" style = "left: 50px; top: 150px;"/span
span id = "spnB" style = "left: 850px; top: 350px;"/span
span id = "spnO"/span
canvas id = "cnvArc" style = "position: absolute; background-color: rgb(255, 255, 0, 0.01); z-index: 1; transform-origin: 0 100%;"/canvas
/body
/html
复制进来的代码都不带缩进的吗?
该代码纯手写,不从第三方处盗用.仅供参考.
html
head
meta charset="utf-8"
/head
body
canvas id="cvs" width="200" height="200"/canvas
script
//扇形对象
CanvasRenderingContext2D.prototype.sector = function (x, y, radius, sDeg, eDeg) {
// 初始保存
this.save();
// 位移到目标点
this.translate(x, y);
this.beginPath();
// 画出圆弧
this.arc(0,0,radius,sDeg, eDeg);
// 再次保存以备旋转
this.save();
// 旋转至起始角度
this.rotate(eDeg);
// 移动到终点，准备连接终点与圆心
this.moveTo(radius,0);
// 连接到圆心
this.lineTo(0,0);
// 还原
this.restore();
// 旋转至起点角度
this.rotate(sDeg);
// 从圆心连接到起点
this.lineTo(radius,0);
this.closePath();
// 还原到最初保存的状态
this.restore();
return this;
}
//执行
function start(degrees){
var ctx = document.getElementById('cvs').getContext('2d');
degrees++;
ctx.sector(100,100,50,0,Math.PI/180*degrees).fill();
if(degrees360){
setTimeout('start('+degrees+')',10);
}else{
alert('画完了')
}
}
start(1)
/script
/body
/html
!DOCTYPE HTML
html
head
meta charset="utf-8" /
title角度转弧度/title
script
var ck = function() {
try {
b.value = eval("Math.PI*" + a.value + "/180");
} catch (e) {
alert("角度输入不正确");
a.focus();
a.select();
}
}
/script
/head
body角度：
input type="text" id="a" /弧度：
input type="text" id="b" /
input type="button" value="转换" onclick="ck()" /
/body
/html
var path = svgdoc.createElement("path");
path.setAttribute("d","M400 400 L400 300 A400 400 90 0 1 500 400 Z");
path.setAttribute("style","fill:none;stroke:#00f;stroke-width:2");
svgdoc.rootElement.appendChild(path);
这个代码是画四分之一个圆，圆环你自己算下坐标，用PATH画，A是画弧线的
path的相关知识，你百度你里面看下，这里就不多说了
HTML canvas arcTo() 方法
Canvas 对象参考手册 Canvas 对象
实例
在画布上创建介于两个切线之间的弧：
JavaScript：
var c=document.getElementById("myCanvas");
var ctx=c.getContext("2d");
ctx.beginPath();
ctx.moveTo(20,20); // 创建开始点
ctx.lineTo(100,20); // 创建水平线
ctx.arcTo(150,20,150,70,50); // 创建弧
ctx.lineTo(150,120); // 创建垂直线
ctx.stroke(); // 绘制
尝试一下 »
浏览器支持
Internet ExplorerFirefoxOperaGoogle ChromeSafari
Internet Explorer 9、Firefox、Chrome 和 Safari 支持 arcTo() 方法。
注意：Opera 不支持 arcTo() 方法。
注意：Internet Explorer 8 及之前的版本不支持 canvas 元素。
定义和用法
arcTo() 方法在画布上创建介于两个切线之间的弧/曲线。
提示：请使用 stroke() 方法在画布上绘制确切的弧。
JavaScript 语法： context.arcTo(x1,y1,x2,y2,r);
参数值
参数 描述
x1 弧的起点的 x 坐标。
y1 弧的起点的 y 坐标。
x2 弧的终点的 x 坐标。
y2 弧的终点的 y 坐标。
r 弧的半径。