<input type="button" value="开始旋转" onclick="spin()" style="float: left" />
<meta http-equiv="Content-Type" content="text/htmlcharset=utf-8" />
<canvas id="wheelcanvas" width="500" height="500"></canvas>
<script type="application/javascript">
var colors = ["#B8D430", "#3AB745", "#029990", "#3501CB",
"#2E2C75", "#673A7E", "#CC0071", "#F80120",
"#F35B20", "#FB9A00", "#FFCC00", "#FEF200"]
var restaraunts = ["北京", "上海", "天津", "南京",
"杭州", "深圳", "武汉", "济南",
"重庆", "大连", "合肥", "郑洲"]
var startAngle = 0
var arc = Math.PI / 6
var spinTimeout = null
var spinArcStart = 10
var spinTime = 0
var spinTimeTotal = 0
var ctx
function draw() {
drawRouletteWheel()
}
function drawRouletteWheel() {
var canvas = document.getElementById("wheelcanvas")
if (canvas.getContext) {
var outsideRadius = 200
var textRadius = 160
var insideRadius = 125
ctx = canvas.getContext("2d")
ctx.clearRect(0,0,500,500)
ctx.strokeStyle = "black"
ctx.lineWidth = 2
ctx.font = 'bold 12px sans-serif'
for(var i = 0i <12i++) {
var angle = startAngle + i * arc
ctx.fillStyle = colors[i]
ctx.beginPath()
ctx.arc(250, 250, outsideRadius, angle, angle + arc, false)
ctx.arc(250, 250, insideRadius, angle + arc, angle, true)
ctx.stroke()
ctx.fill()
ctx.save()
ctx.shadowOffsetX = -1
ctx.shadowOffsetY = -1
ctx.shadowBlur= 0
ctx.shadowColor = "rgb(220,220,220)"
ctx.fillStyle = "black"
ctx.translate(250 + Math.cos(angle + arc / 2) * textRadius, 250 + Math.sin(angle + arc / 2) * textRadius)
ctx.rotate(angle + arc / 2 + Math.PI / 2)
var text = restaraunts[i]
ctx.fillText(text, -ctx.measureText(text).width / 2, 0)
ctx.restore()
}
//Arrow
ctx.fillStyle = "black"
ctx.beginPath()
ctx.moveTo(250 - 4, 250 - (outsideRadius + 5))
ctx.lineTo(250 + 4, 250 - (outsideRadius + 5))
ctx.lineTo(250 + 4, 250 - (outsideRadius - 5))
ctx.lineTo(250 + 9, 250 - (outsideRadius - 5))
ctx.lineTo(250 + 0, 250 - (outsideRadius - 13))
ctx.lineTo(250 - 9, 250 - (outsideRadius - 5))
ctx.lineTo(250 - 4, 250 - (outsideRadius - 5))
ctx.lineTo(250 - 4, 250 - (outsideRadius + 5))
ctx.fill()
}
}
function spin() {
spinAngleStart = Math.random() * 10 + 10
spinTime = 0
spinTimeTotal = Math.random() * 3 + 4 * 1000
rotateWheel()
}
function rotateWheel() {
spinTime += 30
if(spinTime >= spinTimeTotal) {
stopRotateWheel()
return
}
var spinAngle = spinAngleStart - easeOut(spinTime, 0, spinAngleStart, spinTimeTotal)
startAngle += (spinAngle * Math.PI / 180)
drawRouletteWheel()
spinTimeout = setTimeout('rotateWheel()', 30)
}
function stopRotateWheel() {
clearTimeout(spinTimeout)
var degrees = startAngle * 180 / Math.PI + 90
var arcd = arc * 180 / Math.PI
var index = Math.floor((360 - degrees % 360) / arcd)
ctx.save()
ctx.font = 'bold 30px sans-serif'
var text = restaraunts[index]
ctx.fillText(text, 250 - ctx.measureText(text).width / 2, 250 + 10)
ctx.restore()
}
function easeOut(t, b, c, d) {
var ts = (t/=d)*t
var tc = ts*t
return b+c*(tc + -3*ts + 3*t)
}
draw()
</script>
用css3还是Canvas？自己写还是用引擎？用引擎的话用哪个？不管用什么方法做，首先数据层都是一样的，比如一个圆盘分成n个扇形图块；转盘转起来，其实就是定时点亮一个新图块，同时恢复之前点亮的图块。写到这里，我发现和扇形的角度没有任何关系，甚至不用html5技术也能做。
一款JS+html5转盘抽奖代码网页特效，该特效代码基于html5 canvas技术实现，点击开始旋转按钮，转盘就会快速旋转，停止旋转后，所在区域就是中奖项目。奖项可以自定义。请用支持HTML5+CSS3主流浏览器预览效果。（兼容测试：FireFox、Chrome、Safari、Opera等支持HTML5/CSS3浏览器）使用方法：
1、调用CSS样式：
<link rel="stylesheet" type="text/css" href="css/style.css" />
2、添加HTML代码：
将<!--效果html开始-->......<!--效果html结束-->之间的html和js代码；放在<body></body>之间。
