javascript HTML5 Canvas实现圆盘抽奖功能

我们经常参加各种电商优惠活动，比如购买达到一定数额进行抽奖活动，在比如微信抽奖，淘宝抽奖，迅雷赚钱宝圆盘抽奖活动等。这些抽奖活动部分就是由HTML5的Canvas来制作的，今天就为大家分享一下如何使用HTML5的Canvas来制作圆盘抽奖功能。老规矩，先看下效果图吧：
再来看看Canvas的几个主要api：
全部源代码如下：
<！DOCTYPE html><html lang="zh-cn"><head><meta charset="UTF-8"><title>HTML5 Canvas圆盘抽奖应用DEMO演示</title><meta name="viewport" content="width=device-width, initial-scale=1, user-scalable=no"><style>*{padding: 0px;margin: 0px;font-size: 16px;font-family: "Microsoft YaHei";}.xttblog_box{width: 300px;height: 300px;margin: 100px auto;position: relative; }.xttblog_box canvas{position: absolute;}#xttblog{background-color: white;border-radius: 100%;}#xttblog01,#xttblog03{left: 50px;top: 50px;z-index: 30;}#xttblog02{left: 75px;top: 75px;z-index: 20;}#xttblog{-o-transform: transform 6s;-ms-transform: transform 6s;-moz-transform: transform 6s;-webkit-transform: transform 6s;transition: transform 6s;-o-transform-origin: 50% 50%;-ms-transform-origin: 50% 50%;-moz-transform-origin: 50% 50%;-webkit-transform-origin: 50% 50%;transform-origin: 50% 50%;}.taoge_btn{width: 60px;height: 60px;left: 120px;top: 120px;border-radius: 100%;position: absolute;cursor: pointer;border: none;background: transparent;outline: none;z-index: 40;}</style><script type="text/javascript" src="http://cdn.bootcss.com/jquery/1.11.3/jquery.min.js"></script><script>$（document）.ready（function（）{ //旋转角度 var angles; //可抽奖次数 var clickNum = 5; //旋转次数 var rotNum = 0; //中奖公告 var notice = null; //转盘初始化 var color = ["#626262","#787878","rgba（0,0,0,0.5）","#DCC722","white","#FF4350"]; var info = ["谢谢参与"," 1000"," 10"," 500"," 100"," 4999"," 1"," 20"]; var info1 = ["再接再厉","元","元"," 淘金币","元"," 淘金币","元"," 淘金币"] canvasRun（）; $（"#tupBtn"）.bind（"click",function（）{if （clickNum >= 1） { //可抽奖次数减一 clickNum = clickNum-1; //转盘旋转 runCup（）; //转盘旋转过程“开始抽奖”按钮无法点击 $（"#tupBtn"）.attr（"disabled", true）; //旋转次数加一 rotNum = rotNum + 1; //“开始抽奖”按钮无法点击恢复点击 setTimeout（function（）{alert（notice）;$（"#tupBtn"）.removeAttr（"disabled", true）; },6000）;}else{ alert（"亲，抽奖次数已用光！"）;} }）;//转盘旋转 function runCup（）{probability（）;var degValue = "rotate（"+angles+"deg"+"）";$（"#xttblog"）.css（"-o-transform",degValue）; //Opera$（"#xttblog"）.css（"-ms-transform",degValue）; //IE浏览器$（"#xttblog"）.css（"-moz-transform",degValue）; //Firefox$（"#xttblog"）.css（"-webkit-transform",degValue）;//Chrome和Safari$（"#xttblog"）.css（"transform",degValue）; }//各奖项对应的旋转角度及中奖公告内容 function probability（）{//获取随机数var num = parseInt（Math.random（）*（7 - 0 + 0） + 0）;//概率if （ num == 0 ） { angles = 2160 * rotNum + 1800; notice = info[0] + info1[0];}//概率else if （ num == 1 ） { angles = 2160 * rotNum + 1845; notice = info[7] + info1[7];}//概率else if （ num == 2 ） { angles = 2160 * rotNum + 1890; notice = info[6] + info1[6];}//概率else if （ num == 3 ） { angles = 2160 * rotNum + 1935; notice = info[5] + info1[5];}//概率else if （ num == 4 ） { angles = 2160 * rotNum + 1980; notice = info[4] + info1[4];}//概率else if （ num == 5 ） { angles = 2160 * rotNum + 2025; notice = info[3] + info1[3];}//概率else if （ num == 6 ） { angles = 2160 * rotNum + 2070; notice = info[2] + info1[2];}//概率else if （ num == 7 ） { angles = 2160 * rotNum + 2115; notice = info[1] + info1[1];} }//绘制转盘 function canvasRun（）{var canvas=document.getElementById（"xttblog"）;var canvas01=document.getElementById（"xttblog01"）;var canvas03=document.getElementById（"xttblog03"）;var canvas02=document.getElementById（"xttblog02"）;var ctx=canvas.getContext（"2d"）;var ctx1=canvas01.getContext（"2d"）;var ctx3=canvas03.getContext（"2d"）;var ctx2=canvas02.getContext（"2d"）;createCircle（）;createCirText（）;initPoint（）;//外圆function createCircle（）{ var startAngle = 0;//扇形的开始弧度 var endAngle = 0;//扇形的终止弧度 //画一个8等份扇形组成的圆形 for （var i = 0; i< 8; i++）{startAngle = Math.PI*（i/4-1/8）;endAngle = startAngle+Math.PI*（1/4）;ctx.save（）;ctx.beginPath（）;ctx.arc（150,150,100, startAngle, endAngle, false）;ctx.lineWidth = 120;if （i%2 == 0） { ctx.strokeStyle = color[0];}else{ ctx.strokeStyle = color[1];}ctx.stroke（）;ctx.restore（）; }} //各奖项function createCirText（）{ctx.textAlign="start"; ctx.textBaseline="middle"; ctx.fillStyle = color[3]; var step = 2*Math.PI/8; for （ var i = 0; i < 8; i++） {ctx.save（）;ctx.beginPath（）;ctx.translate（150,150）;ctx.rotate（i*step）;ctx.font = " 20px Microsoft YaHei";ctx.fillStyle = color[3];ctx.fillText（info[i],-30,-115,60）;ctx.font = " 14px Microsoft YaHei";ctx.fillText（info1[i],-30,-95,60）;ctx.closePath（）;ctx.restore（）; }} function initPoint（）{ //箭头指针 ctx1.beginPath（）; ctx1.moveTo（100,24）; ctx1.lineTo（90,62）; ctx1.lineTo（110,62）; ctx1.lineTo（100,24）; ctx1.fillStyle = color[5]; ctx1.fill（）; ctx1.closePath（）; //中间小圆 ctx3.beginPath（）; ctx3.arc（100,100,40,0,Math.PI*2,false）; ctx3.fillStyle = color[5]; ctx3.fill（）; ctx3.closePath（）; //小圆文字 ctx3.font = "Bold 20px Microsoft YaHei"; ctx3.textAlign="start"; ctx3.textBaseline="middle"; ctx3.fillStyle = color[4]; ctx3.beginPath（）; ctx3.fillText（"开始",80,90,40）; ctx3.fillText（"抽奖",80,110,40）; ctx3.fill（）; ctx3.closePath（）; //中间圆圈 ctx2.beginPath（）; ctx2.arc（75,75,75,0,Math.PI*2,false）; ctx2.fillStyle = color[2]; ctx2.fill（）; ctx2.closePath（）;} }}）;</script></head><body><div class="xttblog_box"> <canvas id="xttblog" width="300px" height="300px">抱歉！浏览器不支持。</canvas> <canvas id="xttblog01" width="200px" height="200px">抱歉！浏览器不支持。</canvas> <canvas id="xttblog03" width="200px" height="200px">抱歉！浏览器不支持。</canvas> <canvas id="xttblog02" width="150px" height="150px">抱歉！浏览器不支持。</canvas> <button id="tupBtn" class="taoge_btn"></button></div><！-- 更改系统默认弹窗 --><script type="text/javascript">window.alert = function（str）{ var shield = document.createElement（"DIV"）; shield.id = "shield"; shield.style.position = "absolute"; shield.style.left = "50%"; shield.style.top = "50%"; shield.style.width = "280px"; shield.style.height = "150px"; shield.style.marginLeft = "-140px"; shield.style.marginTop = "-110px"; shield.style.zIndex = "25"; var alertFram = document.createElement（"DIV"）; alertFram.id="alertFram"; alertFram.style.position = "absolute"; alertFram.style.width = "280px"; alertFram.style.height = "150px"; alertFram.style.left = "50%"; alertFram.style.top = "50%"; alertFram.style.marginLeft = "-140px"; alertFram.style.marginTop = "-110px"; alertFram.style.textAlign = "center"; alertFram.style.lineHeight = "150px"; alertFram.style.zIndex = "300"; strHtml = "<ul style="list-style:none;margin:0px;padding:0px;width:100%">
"; strHtml += " <li style="background:#626262;text-align:left;padding-left:20px;font-size:14px;font-weight:bold;height:25px;line-height:25px;border:1px solid #F9CADE;color:white">[中奖提醒]</li>
"; strHtml += " <li style="background:#787878;text-align:center;font-size:12px;height:95px;line-height:95px;border-left:1px solid #F9CADE;border-right:1px solid #F9CADE;color:#DCC722">"+str+"</li>
"; strHtml += " <li style="background:#626262;text-align:center;font-weight:bold;height:30px;line-height:25px; border:1px solid #F9CADE;"><input type="button" value="确 定" onclick="doOk（）" style="width:80px;height:20px;background:#626262;color:white;border:1px solid white;font-size:14px;line-height:20px;outline:none;margin-top: 4px"/></li>
"; strHtml += "</ul>
"; alertFram.innerHTML = strHtml; document.body.appendChild（alertFram）; document.body.appendChild（shield）; this.doOk = function（）{alertFram.style.display = "none";shield.style.display = "none"; } alertFram.focus（）; document.body.onselectstart = function（）{return false;};}</script></body></html>
以上就是本文的全部内容，希望对大家的学习有所帮助。
原文地址：http://www.xttblog.com/?p=399