绝对值得看的来篇，哈哈。本人亲自完成，有错误请大家指出：
现在的手机完美支持html5,所以如果手机端想要做个抽奖模块的话,用刮刮卡抽奖效果,相信这个互动体验是非常棒的
ps:由于本人没有wp8系统的手机,所以没法兼容wp8系统的,目前完美兼容android,IOS
如果要在pc浏览的话，得改下js,目前支持谷歌，火狐，ie>=10,如果网友想要的话我就去写个
代码如下:
代码如下:
eraser effect
(function() {
window.onload = function(){
/**判断浏览器是否支持canvas**/
try{
document.createElement('canvas').getContext('2d');
}catch(e){
var addDiv = document.createElement('div');
alert('您的手机不支持刮刮卡效果哦~!');
}
};
var u = navigator.userAgent,mobile = '';
if(u.indexOf('iPhone') > -1) mobile = 'iphone';
if(u.indexOf('Android') > -1 || u.indexOf('Linux') > -1) mobile = 'Android';
function createCanvas(parent, width, height) {
var canvas = {};
canvas.node = document.createElement('canvas');
canvas.context = canvas.node.getContext('2d');
canvas.node.width = width || 100;
canvas.node.height = height || 100;
parent.appendChild(canvas.node);
return canvas;
}
function init(container, width, height, fillColor, type) {
var canvas = createCanvas(container, width, height);
var ctx = canvas.context;
// define a custom fillCircle method
ctx.fillCircle = function(x, y, radius, fillColor) {
this.fillStyle = fillColor;
this.beginPath();
this.moveTo(x, y);
this.arc(x, y, radius, 0, Math.PI * 2, false);
this.fill();
};
ctx.clearTo = function(fillColor) {
ctx.fillStyle = fillColor;
ctx.fillRect(0, 0, width, height);
};
ctx.clearTo(fillColor || "#ddd");
canvas.node.addEventListener("touchstart",function(e){
canvas.isDrawing = true;
},false);
canvas.node.addEventListener("touchend",function(e){
canvas.isDrawing = false;
},false);
canvas.node.addEventListener("touchmove",function(e){
if (!canvas.isDrawing) {
return;
}
if(type == 'Android'){
var x = e.changedTouches[0].pageX - this.offsetLeft;
var y = e.changedTouches[0].pageY - this.offsetTop;
}else{
var x = e.pageX - this.offsetLeft;
var y = e.pageY - this.offsetTop;
}
var radius = 20;
var fillColor = '#ff0000';
ctx.globalCompositeOperation = 'destination-out';
ctx.fillCircle(x, y, radius, fillColor);
},false);
}
var container = document.getElementById('canvas');
init(container, 531, 438, '#ff0000', mobile);
})();