sgWatermark.js源码 

import html2canvas from 'html2canvas'; // npm install --save html2canvas (官网：https://html2canvas.hertzen.com)
export default {addWatermark({container = document.body, // 水印添加到的容器innerHTML = "水印文字内容", // 水印文字的内容rotate = -30,//默认文字旋转角度cssText = `box-sizing: border-box;width: max-content;height: max-content;padding: 30px;font-size: 12px;font-family: 'Microsoft YaHei';color: #00000022;transform-origin:center;transform: rotate(-30deg);z-index: 999999;pointer-events: none;display: flex;justify-content: center;align-items: center;`,//水印模板文本的默认样式className = '__sgWatermark__',//水印类名} = {}) {let dom = document.createElement("div");dom.innerHTML = innerHTML;dom.style.cssText = cssText;//默认样式dom.style.transform = `rotate(${rotate}deg)`;//旋转角度container.appendChild(dom);//添加模板文本// ----------------------------------------html2canvas(dom, { backgroundColor: 'transparent', logging: false, }).then(canvas => {dom.parentNode.removeChild(dom);//移除模板文本let base64Url = canvas.toDataURL('image/png', 1.0);const __sgWatermark__ = document.querySelector(`.${className}`);const watermarkDiv = __sgWatermark__ || document.createElement("div");watermarkDiv.style.cssText = `transition: .618s ease;opacity: 0;position: fixed; top: 0; left: 0; bottom: 0; right: 0; pointer-events: none; z-index: 999999999; background: url(${base64Url}); `;setTimeout(() => {watermarkDiv.style.opacity = 1;//缓慢出现}, 0);watermarkDiv.className = className;__sgWatermark__ || container.insertBefore(watermarkDiv, container.firstChild);});},removeWatermark(className = '__sgWatermark__',//水印类名) {const dom = document.querySelector(`.${className}`);dom.parentNode.removeChild(dom);},
};

示例

<template><div :class="$options.name"><el-button type="primary" style="width: 300px; height: 100px">主要按钮</el-button><divref="div"style="width: 600px;height: 300px;background-color: #00000011;display: flex;justify-content: center;align-items: center;">局部div</div></div>
</template>
<script>
import sgWatermark from "@/js/sgWatermark";
export default {mounted() {// 示例1sgWatermark.addWatermark();// 示例2// sgWatermark.addWatermark({ container: this.$el, innerHTML: `高启强（No:201314）` });// 示例3// sgWatermark.addWatermark({ container: this.$refs.div, innerHTML: `<b style="color: #F56C6C88;font-weight: bold;font-size: 24px;" >你挚爱的强哥</b>` });},
};
</script>