用canvas实现刮刮乐刮奖效果
<!DOCTYPE HTML>
<html>
<head>
<meta charset="utf-8">
<meta name="viewport" content="width=device-width,initial-scale=1.0">
<title>刮刮乐</title>
<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">
<div class="msg">请刮开灰色部分，<a href="javascript:void(0)" onClick="window.location.reload()">再来一次</a></div>
<div class="demo">
<canvas></canvas>
</div>
</div>
<script type="text/javascript">
var bodyStyle = document.body.style;
//禁用页面的鼠标选中拖动的事件，就是不运行执行选中操作
bodyStyle.mozUserSelect = 'none';
bodyStyle.webkitUserSelect = 'none';
var img = new Image();
var canvas = document.querySelector('canvas');
// canvas.mozUserSelect = 'none';
// canvas.webkitUserSelect = 'none';
canvas.style.position = 'absolute';
var imgs = ['./17.jpg','./23.gif'];//这里放置图片，图片位于刮层下面
var num = Math.floor(Math.random() * 2);
img.src = imgs[num];
img.addEventListener('load', function (e) {
var ctx;
var w = img.width*1.5,
h = img.height;//刮层的大小可以自行调整
var offsetX = canvas.offsetLeft,
offsetY = canvas.offsetTop;
var mousedown = false;
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[0];
}
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();
}
}
}
canvas.width = w;
canvas.height = h;
canvas.style.backgroundImage = 'url(' + img.src + ')';
canvas.style.backgroundSize = "100% 100%";//设置填充效果
ctx = canvas.getContext('2d');
ctx.fillStyle = 'gray';
ctx.fillRect(0, 0, w, h);
// 在前面银色图像下面画图
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>
付明旭
