不是原创,微信公众号看到的,做个小笔记:
直接上代码了
watemark.js
var watermark = {};
function setWatermark(args) {
//声明一个怪异一点的变量，确保id的唯一性
var id = '111.222.333.456';
var xIndex = 15;//绘制文本的 x 坐标位置
var yIndex = 65;//绘制文本的 y 坐标位置
var xInterval = 25//有多个参数时的行间间隔
if (document.getElementById(id) !== null) {
document.body.removeChild(document.getElementById(id));
}
//利用canvas绘制水印信息
var can = document.createElement('canvas');
can.width = 250;
can.height = 150;
var cans = can.getContext('2d');
cans.rotate(-20 * Math.PI / 180);
cans.font = '17px Vedana';
// ziti yanse
cans.fillStyle = 'rgba(200, 200, 200, 0.30)';
cans.textAlign = 'left';
cans.textBaseline = 'Middle';
for (let i = 0; i < args.length; i++) {
cans.fillText(args[i], xIndex, yIndex); //绘制水印文案
yIndex += xInterval;//设置每行间隔
}
//创建div用于显示
var div = document.createElement('div');
div.id = id;
div.style.pointerEvents = 'none';
div.style.top = '70px';
div.style.left = '90px';
div.style.position = 'fixed';
div.style.zIndex = '100000';
div.style.width = document.documentElement.clientWidth - 50 + 'px';
div.style.height = document.documentElement.clientHeight - 50 + 'px';
//div承载水印显示
div.style.background = 'url(' + can.toDataURL('image/png') + ') left top repeat';
document.body.appendChild(div);
return id;
}
watermark.set = function(){
let args = Array.prototype.slice.apply(arguments);
let id = setWatermark(args);
// 检测如果水印被去掉了，自动给加上
setInterval(function () {
if (document.getElementById(id) === null) {
id = setWatermark(args);
}
}, 500)
//在窗口大小改变之后,自动触发加水印事件
window.onresize = function () {
setWatermark(args);
}
}
window.watermark = watermark;
xxx.html:
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<meta http-equiv="X-UA-Compatible" content="ie=edge">
<title>Document</title>
<script src="watermark.js"></script>
</head>
<body>
<script>
window.onload = () => {
//添加水印
watermark.set("水印信息1", "我是水印信息2", "...");
}
</script>
</body>
</html>