<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta http-equiv="X-UA-Compatible" content="IE=edge">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<title>Document</title>
</head>
<body id="waterWrapper">
<canvas id="canvas"></canvas>
<script>
function drawWaterPrint(){
const canvas = document.getElementById('canvas');
canvas.width = 200;
canvas.height = 200;
canvas.style.display = 'none';
const ctx = canvas.getContext('2d');
ctx.font ='16px Microsoft JhengHei';
ctx.fillStyle ='rgba(0,0,0,.3)';
ctx.rotate(-0.3) ;
ctx.fillText('大东在路上',canvas.width / 8,canvas.height / 4);
// ctx.fillText('大东在路上',20,20);
const img = canvas.toDataURL('image/png' )
const style =`background-image:url(${img})`
if(style !== waterWrapper.style){
waterWrapper.setAttribute( 'style',style);
}
}
drawWaterPrint()
function callback(){
drawWaterPrint()
}
const observer = new MutationObserver(callback)
const targetNode = waterWrapper // 监听节点
const config = {attributes : true} // 监听属性
observer.observe(targetNode,config)
</script>
</body>
</html>
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