js地区转盘抽奖插件

<script type="text/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 = 0; i < 12; i++) {
          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>