已下为刮刮乐源码，转载请表明出处
<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<meta name="viewport" content="initial-scale=1.0, maximum-scale=1.0, user-scalable=no" />
<title>demo</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: #df412b;
position: relative;
}
.banner1{
display: block;
width: 100%;
height: auto;
overflow: hidden;
visibility: 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%;
}
.canvas{
position:absolute;
top:2px;
left:2.5%;
width:95%;
height:82px;
line-height:82px;
text-align:center;
z-index: 2;
}
.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;
}
.num{
width: 100%;
height: 30px;
line-height: 30px;
text-align: center;
font-size:14px;
margin-top: 5%;
}
#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>
</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" />-->
<!-- 遮罩层1抽奖次数已经用完-->
<div class="pop pop1">
<img src="img/pop1.png" />
</div>
<div class="pop pop2">
<img src="img/pop2.png" id="pop2" />
</div>
<script>
//控制刮卡次数
var t = 1;
//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"
alert("逗你玩，别当真哦~");
};
}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("刮刮乐",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);
console.log(a.data);
console.log(a.data.length);
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>
</body>
</html>
