添加水印

创建JS文件watermark.js

let watermark = {}

let setWatermark = (arr) => {
    let id = '1.23452384164.123412416';

    if (document.getElementById(id) !== null) {
        document.body.removeChild(document.getElementById(id));
    }

    //创建一个画布
    let can = document.createElement('canvas');
    //设置画布的长宽
    can.width = 300;
    can.height = 150;

    let cans = can.getContext('2d');
    //旋转角度
    cans.rotate(10 * Math.PI / 180);
    cans.font = '20px Vedana';
    //设置填充绘画的颜色、渐变或者模式
    cans.fillStyle = 'rgba(200, 200, 200, 0.40)';
    //设置文本内容的当前对齐方式
    cans.textAlign = 'left';
    //设置在绘制文本时使用的当前文本基线
    cans.textBaseline = 'Middle';
    //循环遍历数组，分别绘制每行文字
    arr.forEach((text, index) => {
        cans.fillText(text, can.width / 8, can.height / 2 + index * 30);
    });

    let div = document.createElement('div');
    div.id = id;
    div.style.pointerEvents = 'none';
    div.style.top = '30px';
    div.style.left = '0px';
    div.style.opacity = '0.8';
    div.style.position = 'fixed';
    div.style.zIndex = '1';
    div.style.width = document.documentElement.clientWidth + 'px';
    div.style.height = document.documentElement.clientHeight + 'px';
    div.style.background = 'url(' + can.toDataURL('image/png') + ') left top repeat';
    document.body.appendChild(div);
    return id;
}

// 该方法只允许调用一次
watermark.set = (arr) => {
    let id = setWatermark(arr);
    setTimeout(() => {
        if (document.getElementById(id) === null) {
            id = setWatermark(arr);
        }
    }, 500);
    window.onresize = () => {
        setWatermark(arr);
    };
}

export default watermark;

在使用的文件中引用该js

import Watermark from './watermark'

    //初始化加载
  mounted() {
    let username = '要展示的名字'
    let mydate = new Date().toLocaleDateString() 
    Watermark.set([`${username}`, '想要展示啥', `${mydate}`]);
  },