<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8" />
<meta name="viewport" content="width=device-width, initial-scale=1.0, minimum-scale=1.0, maximum-scale=1.0" />
<title>eraser effect</title>
<script type="text/javascript" src="jquery.core.js"></script>
<style>
#canvas {
background:url(winning-ticket.jpg);<!--獎品圖片-->
width: 531px;
height: 438px;
}
.before{
background:none !important;
}
#canvas canvas {
cursor: url("hand.png") 0 0, auto;<!--PC端的手勢圖片-->
}
</style>
</head>
<body oncontextmenu="return false;" onselectstart="return false;">
<div id="canvas"></div>
</body>
<script type="text/javascript">
(function() {
window.onload = function(){
/**判斷瀏覽器是否支持canvas**/
try{
document.createElement('canvas').getContext('2d');
}catch(e){
var addDiv = document.createElement('div');
alert('您的手機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);
})();
</script>
</html>
