<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<title>audio</title>
<style type="text/css">
canvas {
/* canvas 默認寬高 300*150
css設置的寬高，只能設置canvas對象在頁面顯示的大小。
並不能增加畫布內部的像素數
*/
margin: 0 auto;
position: absolute;
left: 0;
top: 0;
}
div {
width: 500px;
height: 500px;
background: url("https://timgsa.baidu.com/timg?image&quality=80&size=b9999_10000&sec=1566357763988&di=bcf0827252aa1c8bab453020de5ec75b&imgtype=0&src=http%3A%2F%2Fimg.zcool.cn%2Fcommunity%2F0128475543010c0000019ae92b7605.jpg%401280w_1l_2o_100sh.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>
<!-- 在標籤上添加canvas像素值 -->
<div>
<p>一等獎</p>
<canvas id="canvasId" width="500" height="500">您的瀏覽器不支持canvas！</canvas>
</div>
<script type="text/javascript">
var cv = document.getElementById("canvasId"),
p = document.getElementsByTagName("p")[0],
ct = cv.getContext("2d");
p.innerText = "一等獎";
//繪製背景色
ct.fillStyle = "#aaa";
ct.fillRect(0, 0, 500, 500);
//設置繪製狀態
ct.lineCap = "round"; //設置線條兩端爲圓弧
ct.lineWidth = 60; //畫筆寬度
/*設置新繪製清除新繪製內容和原內容的重疊區域*/
ct.globalCompositeOperation = "destination-out";
//繪製曲線
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();
//更新座標
lx = e.offsetX;
ly = e.offsetY;
}
}
cv.onmouseup = function (e) {
flag = false;
}
</script>
</html>
canvas 刮刮樂效果
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