H5的Canvas实现刮刮卡效果。 刮开之后是随机生成的8位码。
IE8不行...
<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<meta http-equiv="X-UA-Compatible" content="IE=edge">
<meta name="viewport" content="width=device-width, initial-scale=1">
<title>HTML5 刮刮卡</title>
<link rel="stylesheet" type="text/css" href="" />
<style type="text/css">
.demo{width:320px; margin:10px auto 20px auto; min-height:300px;}
.msg{text-align:center; height:32px; line-height:32px; font-weight:bold; margin-top:50px}
</style>
</head>
<body>
<div id="main">
<h2 align="center">HTML5 刮刮卡(支持手机)</a></h2>
<div class="msg">刮开灰色部分看看，<a href="javascript:void(0)" onClick="window.location.reload()">再来一次</a></div>
<div class="demo">
<canvas id="canvasBotm"></canvas>
<canvas id="canvasTop"></canvas>
</div>
</div>
<script type="text/javascript">
//生成随机数据。n表示位数
var jschars = ['0','1','2','3','4','5','6','7','8','9','A','B','C','D','E','F','G','H','I','J','K','L','M','N','O','P','Q','R','S','T','U','V','W','X','Y','Z','a','b','c','d','e','f','g','h','i','j','k','l','m','n','o','p','q','r','s','t','u','v','w','x','y','z'];
function generateMixed(n) {
var res = "";
for(var i = 0; i < n ; i ++) {
var id = Math.ceil(Math.random()*61);
res += jschars[id];
}
//alert(res);
return res;
}
//禁用页面的鼠标选中拖动的事件
var bodyStyle = document.body.style;
bodyStyle.mozUserSelect = 'none';
bodyStyle.webkitUserSelect = 'none';
//定义图片类，获取canvas元素，并设置背景和位置属性
var img = new Image();
var canvas = document.getElementById('canvasTop');
var canvasBotm = document.getElementById('canvasBotm');
canvas.style.backgroundColor='transparent';
canvas.style.position = 'absolute';
canvasBotm.style.backgroundColor='#f3f3f3'; //验证码背景色
canvasBotm.style.position = 'absolute';
var imgs = ['p_0.jpg','p_1.jpg'];
var num = Math.floor(Math.random()*2);
img.src = imgs[num];
img.addEventListener('load', function(e) {
var ctx;
var w = img.width,
h = img.height;
var offsetX = canvas.offsetLeft,
offsetY = canvas.offsetTop;
var mousedown = false;
//函数layer()用来绘制一个灰色的正方形
function layer(ctx) {
ctx.fillStyle = 'grey';
ctx.fillRect(0, 0, w, h);
}
function layerBotm(ctxBotm) {
ctxBotm.fillStyle = 'grey';
ctxBotm.fillRect(0, 0, w, h);
}
//定义了按下事件
function eventDown(e){
e.preventDefault();
mousedown=true;
}
//定义了松开事件
function eventUp(e){
e.preventDefault();
mousedown=false;
}
//定义了移动事件
function eventMove(e){
e.preventDefault();
if(mousedown) { //当按下时，获取坐标位移，并通过arc(x, y, 10, 0, Math.PI * 2)来绘制小圆点
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, 10, 0, Math.PI * 2);
fill();
}
}
}
//通过canvas调用以上函数，绘制图形，并且侦听触控及鼠标事件，调用相应的函数
canvas.width=w;
canvas.height=h;
canvasBotm.width=w;
canvasBotm.height=h;
//canvas.style.backgroundImage='url('+img.src+')';
//canvas.style.backgroundColor='#f3f3f3';
ctxBotm=canvas.getContext("2d");
ctx=canvasBotm.getContext("2d");
ctx.font="50px Arial";
// 创建渐变
var gradient=ctx.createLinearGradient(0,0,canvas.width,0);
gradient.addColorStop("0","magenta");
gradient.addColorStop("0.5","blue");
gradient.addColorStop("1.0","red");
//实习字体
ctx.fillStyle=gradient;
ctx.fillText(generateMixed(8),40,90);
//空心字体
ctx.strokeStyle=gradient;
ctx.strokeText(generateMixed(8),40,90);
ctx=canvas.getContext('2d');
ctx.fillStyle='transparent';
ctx.fillRect(0, 0, w, h);
layerBotm(ctxBotm);
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);
});
</script>
</body>
</html>
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