html页面水印代码
<script>
//全屏水印代码
function waterMark(){
    let text = "@网上用户";  //水印文字，这里可以改成你自己的
    const canvas = document.createElement("canvas");
    canvas.width = 250;
    canvas.height = 150;
    const ctx = canvas.getContext('2d');
    ctx.rotate(-20*Math.PI/180);
    ctx.font = '18px Arial';
    ctx.fillStyle='rgba(128,128,128,0.12)'; //透明度0.12淡淡的水印
    ctx.fillText(text, 30, 100);
    const waterDiv = document.createElement('div');
    waterDiv.style.cssText = `
    position:fixed;
    top:0;
    left:0;
    width:100%;
    height:100%;
    z-index:9998;
    pointer-events:none;
    background-image:url(${canvas.toDataURL('image/png')});
    background-repeat:repeat;
    `;
    document.body.appendChild(waterDiv);
}
window.onload=waterMark;
</script>