手机端js和html5刮刮卡效果

H5的Canvas实现刮刮卡效果。刮开之后是随机生成的8位码。
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<!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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手机端js和html5刮刮卡效果

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