js实现PC端和移动端刮卡效果

<!DOCTYPE html> <html> <head> <meta charset="utf-8"> <meta name="viewport" content="initial-scale=1.0, maximum-scale=1.0, user-scalable=no" /> <title>小月博客刮刮卡案例分享</title> <script src="http://cdn.bootcss.com/jquery/2.1.4/jquery.min.js"></script> <style type="text/css"> * { padding: 0; margin: 0; list-style: none; } body { background: #E34830; position: relative; } .banner1 { display: block; width: 100%; /*height: auto;*/ overflow: hidden; } .ggl { position: relative; width: 85.6%; height: 90px; margin: -5px auto; background: url(img/ggl.png) no-repeat center center; background-size: 100% 100%; border: 1px solid blue; } .canvas { position: absolute; top: 2px; left: 2.5%; width: 95%; height: 82px; line-height: 82px; text-align: center; z-index: 2; border: 1px solid black; } .info { position: absolute; top: 2px; left: 2.5%; width: 95%; height: 82px; text-align: center; } .info span { display: block; font-size: 18px; } #prompt { line-height: 40px; } .btn { position: relative; width: 50%; height: 35px; line-height: 35px; background: #df412b; color: #fff; border-radius: 5px; margin: 0 auto; z-index: 1; } .guize { display: block; width: 85.6%; height: auto; margin: 5% auto 10% auto; border-radius: 5px; border: 1px solid black; } .num { width: 90%; margin: 0 auto; height: 30px; line-height: 30px; text-align: center; font-size: 14px; margin-top: 5%; border: 1px solid black; } #ok, #no { display: none; } .pop { position: fixed; left: 0; top: 0; z-index: 3; width: 100%; height: 100%; background: rgba(0, 0, 0, 0.6); display: none; } .pop img { width: 100%; height: auto; overflow: hidden; margin: 15% auto; } </style> <script> //控制刮卡次数 var t = 0; //初始化所有数据并且随机产生奖品 var initialize = function() { //剩余刮卡次数 $('.num1').html(4 - t); //随机数 function getRandomNum(lbound, ubound) { return (Math.floor(Math.random() * (ubound - lbound)) + lbound); } var r = getRandomNum(1, 100); var btn = document.getElementsByClassName("btn"); for (var i = 0; i < btn.length; i++) { btn[i].style.zIndex = '1'; } document.getElementById("no").style.display = "none"; document.getElementById("ok").style.display = "none"; //初始化涂抹面积 isOk = 0; if (r < t * 33) { document.getElementById("prompt").innerHTML = "恭喜您，中奖了！" var ok = document.getElementById("ok"); ok.style.display = "block"; //点击领取奖品 ok.onclick = function() { window.location.href = "prize.html" }; } else { document.getElementById("prompt").innerHTML = "很遗憾，未中奖！" document.getElementById("no").style.display = "block"; } }; var c1; //画布 var ctx; //画笔 var ismousedown; //标志用户是否按下鼠标或开始触摸 var isOk = 0; //标志用户是否已经刮开了一半以上 var fontem = parseInt(window.getComputedStyle(document.documentElement, null)["font-size"]); //这是为了不同分辨率上配合@media自动调节刮的宽度 /* 页面加载后开始初始化画布 */ window.onload = function() { initialize(); c1 = document.getElementById("c1"); //这里很关键，canvas自带两个属性width、height,我理解为画布的分辨率，跟style中的width、height意义不同。 //最好设置成跟画布在页面中的实际大小一样 //不然canvas中的坐标跟鼠标的坐标无法匹配 c1.width = c1.clientWidth; c1.height = c1.clientHeight; ctx = c1.getContext("2d"); //PC端的处理 c1.addEventListener("mousemove", eventMove, false); c1.addEventListener("mousedown", eventDown, false); c1.addEventListener("mouseup", eventUp, false); //移动端的处理 c1.addEventListener('touchstart', eventDown, false); c1.addEventListener('touchend', eventUp, false); c1.addEventListener('touchmove', eventMove, false); //初始化 initCanvas(); } //初始化画布，画灰色的矩形铺满 function initCanvas() { //网上的做法是给canvas设置一张背景图片，我这里的做法是直接在canvas下面另外放了个div。 //c1.style.backgroundImage="url(中奖图片.jpg)"; ctx.globalCompositeOperation = "source-over"; ctx.fillStyle = '#aaaaaa'; ctx.fillRect(0, 0, c1.clientWidth, c1.clientHeight); ctx.fill(); ctx.font = "Bold 30px Arial"; ctx.textAlign = "center"; ctx.fillStyle = "#999999"; ctx.fillText("刮一刮", c1.width / 2, 50); //把这个属性设为这个就可以做出圆形橡皮擦的效果 //有些老的手机自带浏览器不支持destination-out,下面的代码中有修复的方法 ctx.globalCompositeOperation = 'destination-out'; } //鼠标按下和触摸开始 function eventDown(e) { e.preventDefault(); ismousedown = true; } //鼠标抬起和触摸结束 function eventUp(e) { e.preventDefault(); //得到canvas的全部数据 var a = ctx.getImageData(0, 0, c1.width, c1.height); var j = 0; for (var i = 3; i < a.data.length; i += 4) { if (a.data[i] == 0) j++; } //当被刮开的区域等于一半时，则可以开始处理结果 if (j >= a.data.length / 8) { isOk = 1; } ismousedown = false; } //鼠标移动和触摸移动 function eventMove(e) { e.preventDefault(); if (ismousedown) { if (e.changedTouches) { e = e.changedTouches[e.changedTouches.length - 1]; } var topY = document.getElementById("top").offsetTop; var oX = c1.offsetLeft, oY = c1.offsetTop + topY; var x = (e.clientX + document.body.scrollLeft || e.pageX) - oX || 0, y = (e.clientY + document.body.scrollTop || e.pageY) - oY || 0; //画360度的弧线，就是一个圆，因为设置了ctx.globalCompositeOperation = 'destination-out'; //画出来是透明的 ctx.beginPath(); ctx.arc(x, y, fontem * 1.2, 0, Math.PI * 2, true); //下面3行代码是为了修复部分手机浏览器不支持destination-out //我也不是很清楚这样做的原理是什么 c1.style.display = 'none'; c1.offsetHeight; c1.style.display = 'inherit'; ctx.fill(); } if (isOk) { var btn = document.getElementsByClassName("btn"); for (var i = 0; i < btn.length; i++) { btn[i].style.zIndex = '3'; } document.getElementsByClassName("btn")[0].style.zIndex = "3"; } } //没有中奖再来一次 $("#no").click(function() { if (t > 3) { //因该弹出遮罩层提示您的次数已经用完了 $('.pop1').show(); $('.pop1 img').click(function() { $('.pop1').hide(); }) } else { t++; //初始化按钮 document.getElementById("no").style.display = "none"; document.getElementById("ok").style.display = "none"; window.onload(); initCanvas(); } }); </script> </head> <body> <img src="img/banner1.png" class="banner1" /> <div class="ggl" id="top"> <div class="info" id="prize"> <span id="prompt"></span> <span class="btn" id="ok">领取奖品</span> <span class="btn" id="no">再来一次</span> </div> <canvas id="c1" class="canvas"></canvas> </div> <div class="num"> 您还有<span class="num1"></span>次刮卡机会 </div> <img src="img/guize.png" class="guize" />  <div class="pop pop1"> <img src="img/pop1.png" /> </div> <div class="pop pop2"> <img src="img/pop2.png" id="pop2" /> </div> </body> </html>

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