1 <!DOCTYPE html>
2 <html>
3 <head>
4 <meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
5 <title>html5 canvas圆形转盘抽奖特</title>
6 </head>
7 <body>
8 <div style="width:400px;margin:40px auto 0 auto;">
9 <canvas id='bg'></canvas>
10 </div>
11 <script type="text/javascript">
12 var fillStyle =
13 //['rgb(255,2,0)','rgb(246,150,30)','rgb(255,255,1)','rgb(154,205,52)','rgb(34,145,103)','rgb(30,156,144)','rgb(2,128,255)','rgb(53,52,154)','rgb(128,1,128)','rgb(200,23,131)']
14 ['rgb(220,0,140)','rgb(250,210,50)','rgb(220,0,140)','rgb(250,210,50)','rgb(220,0,140)','rgb(250,210,50)','rgb(220,0,140)','rgb(250,210,50)','rgb(220,0,140)','rgb(250,210,50)']
15 ,fillText = ['一等奖','二等奖','三等奖','四等奖','五等奖','六等奖','七等奖','八等奖','九等奖','十等奖']
16 ,width = 400
17 ,height = 400
18 ,c_x = 200
19 ,c_y =200
20 ,radius = 180 // 圆盘半径
21 ,canvas = document.getElementById('bg')
22 ,index =0
23 ,timer = null
24 ,running = false // 是否运行中
25 ,speed = 300 // 速度
26 ,isBeginPrize = false // 是否开始抽奖
27 ,stepping=0 // 步数，经过一个扇形为1步
28 ,basecircle = 3 // 点击开始时，圆盘旋转的圈数，旋转玩指定圈数之后，再根据selected的值确定奖项
29 ,selected =0; // 最终选中第几个扇形，也就是确定几等奖
30
31 function setup(){
32 drawCircle(false);
33 }
34
35 function drawCircle(isRunning){
36 var deg = Math.PI/300;
37 var startAngle = 0;
38 var endAngle = 58;
39 canvas.height = height;
40 canvas.width = width;
41 var ctx=canvas.getContext('2d');
42 for(var i=0;i<10;i++){
43 ctx.beginPath();
44 // 正在运行的时候，改变当前扇形的颜色
45 if(isRunning && index==i)
46 {
47 ctx.fillStyle = 'rgb(255,0,0)';
48 }
49 else
50 {
51 ctx.fillStyle = fillStyle[i];
52 }
53
54 // 绘制扇形
55 ctx.moveTo(c_x,c_y);
56 ctx.arc(c_x,c_y,radius,deg*startAngle,deg*endAngle,false);
57 ctx.fill();
58
59 // 绘制扇形上的文字
60 ctx.font="12px Microsoft YaHei";
61 ctx.fillStyle = '#fff';
62 ctx.textAlign = "center";
63 ctx.fillText(fillText[i],200+Math.cos(deg*(startAngle+30))*150,200+Math.sin(deg*(startAngle+30))*150);
64 startAngle +=60;
65 endAngle +=60;
66 }
67
68 // 绘制中心圆
69 ctx.beginPath();
70 ctx.arc(200,200,50,0,2*Math.PI,1);
71 ctx.fillStyle = 'rgb(255,255,255)';
72 ctx.fill();
73 // 绘制中心圆
74 ctx.font="15px Microsoft YaHei";
75 // 创建渐变
76 var gradient=ctx.createLinearGradient(0,0,width,0);
77 gradient.addColorStop("0","magenta");
78 gradient.addColorStop("0.2","blue");
79 gradient.addColorStop("0.4","red");
80 // 用渐变填色
81 ctx.textAlign = "center";
82 ctx.fillStyle=gradient;
83 ctx.fillText("start",200,195+0);
84 ctx.fillText("立即抽奖",200,200+20);
85 // 绘制中心园边框
86 ctx.strokeStyle = 'rgb(0,0,0)';
87 ctx.lineWidth = 1;
88 ctx.stroke();
89 }
90
91 function rotate(){
92 if(stepping==5){ // 4步之后开始加速
93 clearTimer();
94 speed = +100;
95 timer = setInterval(rotate,speed);
96 }
97
98 if(basecircle>0 && index ==10){ // 基本圈数结束以后，开始随机抽奖
99 index = 0;
100 basecircle--;
101 if(basecircle == 0) // 开始随机抽奖
102 {
103 clearTimer();
104 speed = 300;
105 timer = setInterval(rotate,speed);
106 isBeginPrize = true;
107 }
108 }
109
110 if(isBeginPrize && selected > 0) // 开始抽奖
111 {
112 if(--selected == 0) //到了选择的奖项之后
113 {
114 clearTimer();
115 isStop = true;
116 }
117 else
118 {
119 clearTimer();
120 speed += 100;
121 timer = setInterval(rotate,speed);
122 }
123 }
124 drawCircle(true);
125 index++;
126 stepping++;
127 }
128
129 // 初始化抽奖参数
130 function init()
131 {
132 basecircle = 5;
133 selected = (Math.floor(Math.random() * 10) + 1 );//输出1-10的随机数
134 running= false;
135 isBeginPrize = false;
136 index = index++;
137 stepping = 0;
138 speed = 300;
139 }
140
141 function mouseDown_Start(e){
142 var local = getPointOnCanvas(canvas, e.pageX, e.pageY);
143 if(local.x > 100 && local.x < 300 && local.y>100 && local.y<300) // 中心圆区域
144 {
145 if(running){
146 return;
147 }
148 init();
149 timer = setInterval(rotate,speed);
150 }
151 }
152
153 function clearTimer(){
154 clearInterval(timer);
155 timer = null;
156 }
157
158 function getPointOnCanvas(canvas, x, y) {
159 var bbox =canvas.getBoundingClientRect();
160 return { x:x- bbox.left *(canvas.width / bbox.width),
161 y:y - bbox.top * (canvas.height / bbox.height)
162 };
163 }
164 setup();
165 canvas.addEventListener("mousedown",mouseDown_Start,false);
166 </script>
167 </div>
168 </body>
169 </html>