<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<title>audio</title>
<style type="text/css">
canvas {
/* canvas 默认宽高 300*150
css设置的宽高，只能设置canvas对象在页面显示的大小。
并不能增加画布内部的像素数
*/
border: 1px solid black;
/* width: 500px;
height: 500px; */
margin: 0 auto;
position: absolute;
left: 0;
top: 0;
}
div {
width: 500px;
height: 500px;
background: url("https://ss1.bdstatic.com/70cFvXSh_Q1YnxGkpoWK1HF6hhy/it/u=4210473879,3554842544&fm=27&gp=0.jpg") no-repeat;
background-size: 100% 100%;
position: relative;
}
div p {
font-size: 50px;
line-height: 500px;
text-align: center;
width: 100%;
}
</style>
</head>
<body>
<!-- 在标签上添加canvas像素值 -->
<div>
<p>一等奖</p>
<canvas id="canvasId" width="500" height="500">您的浏览器不支持canvas！</canvas>
</div>
<script type="text/javascript">
var cv = document.getElementById("canvasId"),
p = document.getElementsByTagName("p")[0];
//设置中奖几率
var num = 10000 * Math.random(),
result = "谢谢惠顾";
if (num < 1000) {
result = "三等奖";
}
if (num < 50) {
result = "二等奖";
}
if (num < 5) {
result = "一等奖";
}
p.innerText = result;
try {
var ct = cv.getContext("2d");
//绘制背景色
ct.fillStyle = "#aaa";
ct.fillRect(0, 0, 500, 500);
//设置绘制状态
ct.lineCap = "round"; //设置线条两端为圆弧
ct.lineJoin = "round"; //设置线条转折为圆弧
ct.lineWidth = 60;
/*设置新绘制清除新绘制内容和原内容的重叠区域*/
ct.globalCompositeOperation = "destination-out";
} catch (e) {
console.log(e);
}
//绘制曲线
var flag = false,
lx, ly;
cv.onmousedown = function (e) {
flag = true;
lx = e.offsetX;
ly = e.offsetY;
}
cv.onmousemove = function (e) {
if (flag) {
ct.beginPath();
ct.moveTo(lx, ly);
ct.lineTo(e.offsetX, e.offsetY);
ct.stroke();
ct.closePath();
//更新坐标
lx = e.offsetX;
ly = e.offsetY;
}
}
cv.onmouseup = function (e) {
flag = false;
}
</script>
</html>
