前言
往期文章
本文将讲解 canvas-clip 方法的高级用法,比如 游戏或相册中,有权限查看完整图片或关卡时,点击展示全图
效果图
说明
- 设置图片 blur
- 在图片上盖住一个canvas,它加载正常清晰的图片
- 通过clip(),开始设置裁剪区域为一个小圆,点击“展示全图”时,慢慢调整裁剪区域的大小,直到展示完整图片
代码
- html
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width,initial=1.0,user-scalable=no">
<title>查看全图</title>
<link rel="stylesheet" href="index.css">
</head>
<body>
<div class="blur-box">
<img class="blur-img"
src="https://gimg2.baidu.com/image_search/src=http%3A%2F%2F07.imgmini.eastday.com%2Fmobile%2F20180717%2F20180717221449_f908566137c38a753a8e55cf0d44a372_7.jpeg&refer=http%3A%2F%2F07.imgmini.eastday.com&app=2002&size=f9999,10000&q=a80&n=0&g=0n&fmt=jpeg?sec=1640181264&t=feffa7375872c64946a936481abf913b">
<canvas id="canvas">不支持canvas</canvas>
<div class="button" id="show-button">SHOW</div>
</div>
<script>
const _w = document.body.clientWidth;
const _h = document.body.clientHeight;
const showButton = document.getElementById('show-button');
const canvas = document.getElementById('canvas');
const ctx = canvas.getContext('2d');
canvas.width = _w;
canvas.height = _h;
const radius = 50;
let clipRegion;
let timer = null;
let image = new Image();
image.src = 'https://gimg2.baidu.com/image_search/src=http%3A%2F%2F07.imgmini.eastday.com%2Fmobile%2F20180717%2F20180717221449_f908566137c38a753a8e55cf0d44a372_7.jpeg&refer=http%3A%2F%2F07.imgmini.eastday.com&app=2002&size=f9999,10000&q=a80&n=0&g=0n&fmt=jpeg?sec=1640181264&t=feffa7375872c64946a936481abf913b';
image.onload = () => {
// 随机生成裁剪区位置
clipRegion = { x: Math.random() * (_w - 2 * radius) + radius, y: Math.random() * (_h - 2 * radius) + radius, r: radius };
draw(image, clipRegion);
};
function draw(image, clipRegion) {
ctx.clearRect(0, 0, _w, _h);
ctx.save();
setClipingRegion(clipRegion);
ctx.drawImage(image, 0, 0, _w, _h);
ctx.restore();
}
function setClipingRegion(clipRegion) {
ctx.beginPath();
ctx.arc(clipRegion.x, clipRegion.y, clipRegion.r, 0, Math.PI * 2);
ctx.clip();
}
showButton.addEventListener('click', () => {
// 隐藏按钮
showButton.style.display = 'none';
timer = setInterval(
function () {
clipRegion.r += 20;
draw(image, clipRegion);
if (clipRegion.r >= 2 * Math.max(_w, _h)) {
clearInterval(timer);
timer = null;
}
}, 30);
}, false);
</script>
</body>
</html>
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- css
* {
padding: 0;
margin: 0;
}
html,
body {
height: 100%;
overflow: hidden;
}
.blur-box {
width: 100%;
height: 100%;
position: relative;
}
.blur-img,
#canvas {
display: block;
position: absolute;
left: 0;
right: 0;
}
.blur-img {
width: 100%;
height: 100%;
/*滤镜模糊*/
filter: blur(20px);
z-index: 0;
}
#canvas {
z-index: 1;
}
.button {
display: block;
position: absolute;
z-index: 2;
width: 100px;
height: 30px;
color: #fff;
text-decoration: none;
text-align: center;
line-height: 30px;
border-radius: 5px;
}
#show-button {
left: 0;
right: 0;
bottom: 50px;
background: #085;
margin: 0 auto;
cursor: pointer;
}
#show-button:hover {
background: #074;
}
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