HTML5刮刮乐抽奖卡效果代码基于Html5 canvas+JS制作，刮卡效果实例，效果超赞，兼容PC端和手机平板移动端，电脑端，按住鼠标左键同时滑动鼠标进行刮卡操作，手机平板移动端，手指滑动屏幕即可进行刮卡。
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<title>HTML5刮刮乐抽奖卡效果</title>
</head>
<body>
<canvas/>
<script type="text/javascript">
(function(bodyStyle){
bodyStyle.mozUserSelect = 'none';
bodyStyle.webkitUserSelect = 'none';
var img = new Image();
var canvas = document.querySelector('canvas');
canvas.style.backgroundColor='transparent';
canvas.style.position = 'absolute';
img.addEventListener('load',function(e){
var ctx;
var w = img.width, h = img.height;
var offsetX = canvas.offsetLeft, offsetY = canvas.offsetTop;
var mousedown = false;
function layer(ctx){
ctx.fillStyle = 'gray';
ctx.fillRect(0, 0, w, h);
}
function eventDown(e){
e.preventDefault();
mousedown=true;
}
function eventUp(e){
e.preventDefault();
mousedown=false;
}
function eventMove(e){
e.preventDefault();
if(mousedown){
if(e.changedTouches){
e=e.changedTouches[e.changedTouches.length-1];
}
var x = (e.clientX + document.body.scrollLeft || e.pageX) - offsetX || 0,
y = (e.clientY + document.body.scrollTop || e.pageY) - offsetY || 0;
with(ctx){
beginPath()
arc(x, y, 5, 0, Math.PI * 2);
fill();
}
}
}
canvas.width=w;
canvas.height=h;
canvas.style.backgroundImage='url('+img.src+')';
ctx=canvas.getContext('2d');
ctx.fillStyle='transparent';
ctx.fillRect(0, 0, w, h);
layer(ctx);
ctx.globalCompositeOperation = 'destination-out';
canvas.addEventListener('touchstart', eventDown);
canvas.addEventListener('touchend', eventUp);
canvas.addEventListener('touchmove', eventMove);
canvas.addEventListener('mousedown', eventDown);
canvas.addEventListener('mouseup', eventUp);
canvas.addEventListener('mousemove', eventMove);
});
img.src = 'http://www.baidu.com/img/bdlogo.gif';
})(document.body.style);
</script>
<div style="text-align:center;">
<p><a href="http://www.youcl.com/" target="_blank">优客志</a></p>
</div>
</body>
</html>
