1 <script type="text/javascript">
 2         //绘制椭圆
 3         function ParamEllipse(context, x, y, a, b) {
 4             //max是等于1除以长轴值a和b中的较大者
 5             //i每次循环增加1/max，表示度数的增加
 6             //这样可以使得每次循环所绘制的路径（弧线）接近1像素
 7             var step = (a > b) ? 1 / a : 1 / b;
 8             context.fillStyle = "#ff0000";
 9             context.beginPath();
10             context.moveTo(x + a, y); //从椭圆的左端点开始绘制
11             for (var i = 0; i < 2 * Math.PI; i += step) {
12                 //参数方程为x = a * cos(i), y = b * sin(i)，
13                 //参数为i，表示度数（弧度）
14                 context.lineTo(x + a * Math.cos(i), y + b * Math.sin(i));
15             }
16             context.closePath();
17             context.stroke();
18             context.fill();
19             context.closePath();
20         };
21 
22         //绘制矩形
23         function FillRect(context, x, y, w, h, flag) {
24             var grd = context.createLinearGradient(x+w/2, y, x + w/2, y + h);
25             if (flag) {
26                 grd.addColorStop(0, "yellow");
27                 grd.addColorStop(1, "red");
28             } else {
29                 grd.addColorStop(0, "red");
30                 grd.addColorStop(1, "yellow");
31             }
32             context.fillStyle = grd;
33             context.fillRect(x, y, w, h);
34         }
35 
36         //绘制线条
37         function SetLine(ctx, x, y, x1, y1) {
38             ctx.beginPath();
39             ctx.strokeStyle = "yellow";
40             ctx.moveTo(x,y);
41             ctx.lineTo(x1,y1);
42             ctx.stroke();
43             ctx.closePath();
44         }
45         window.onload = function () {
46             var c = document.getElementById("myCanvas");
47             var ctx = c.getContext("2d");
48             var startX = 150; //中心坐标x
49             var startY = 300; //中心坐标y
50             var pWidth = 120; //椭圆长轴
51             var pHeigth = 80; //椭圆形短轴
52             var fWidth = 120; //矩形宽
53             var fheight = 40; //矩形高
54             //绘制椭圆
55             ParamEllipse(ctx, startX, startY, pWidth, pHeigth);
56             //在椭圆上方和下方绘制长方形，且有一半的高度和椭圆重叠
57             FillRect(ctx, startX - fWidth / 2, startY - pHeigth - (fheight / 2), fWidth, fheight, true);
58             FillRect(ctx, startX - fWidth / 2, startY + pHeigth - (fheight / 2), fWidth, fheight, false);
59             //在矩形下方绘制线条,8个单位一条线,长度为40，均匀分布在矩形下方
60             var lLen = fheight; //画线的范围始终在矩形之下
61             var lInterval = 8; //线与线之间的间隔
62             for (var i = 0; i < (fWidth / 8) + 1; i++) {
63                 SetLine(ctx, startX - fWidth / 2 + i * lInterval, startY + pHeigth + fheight / 2, startX - fWidth / 2 + i * lInterval, startY + pHeigth + fheight / 2 + lLen);
64             }
65             //对三部分进行拆解
66             //1. 上矩形 
67             var right = 380;
68             FillRect(ctx, startX - fWidth / 2 + right, startY - pHeigth - (fheight / 2) - 150, fWidth, fheight, true);
69             //2. 中椭圆
70             ParamEllipse(ctx, startX + right, startY - 50, pWidth, pHeigth);
71             //3. 下矩形
72             FillRect(ctx, startX - fWidth / 2 + right, startY + pHeigth - (fheight / 2) + 50, fWidth, fheight, false);
73             //4. 下线
74             for (var i = 0; i < (fWidth / 8) + 1; i++) {
75                 SetLine(ctx, startX - fWidth / 2 + i * lInterval + right, startY + pHeigth + fheight / 2 + 100, startX - fWidth / 2 + i * lInterval + right, startY + pHeigth + fheight / 2 + lLen + 100);
76             }
77             //画线，将其连接起来
78             var lsX = startX + pWidth + 20;
79             var lsY = startY;
80             var leX = startX + pWidth + 20 + 100;
81             var leY = startY;
82             SetLine(ctx, lsX, startY - 30, leX - 30, leY - 150);
83             SetLine(ctx, lsX, startY - 15, leX, leY - 50);
84             SetLine(ctx, lsX, startY + 15, leX, leY + 100);
85             SetLine(ctx, lsX, startY + 30, leX - 30, leY + 150);
86 
87             //左上标写上说明
88             ctx.font = "35px Arial";
89             var t = "灯笼组成--2016-11-13";
90             ctx.fillText(t, 50, 50);
91         }
92         
93     </script>