添加水印

项目中，需要对特定内容添加水印

 代买实现为：

<template>
  <div>
    <div class="font-size">字体:
      <a class="large-font" @click="setFontSize(16)">大</a>
      <el-divider direction="vertical"></el-divider>
      <a class="med-font" @click="setFontSize(14)">中</a>
      <el-divider direction="vertical"></el-divider>
      <a class="small-font" @click="setFontSize(12)">小</a>
    </div>
    <div id="waterLaw" v-html="text" :style="{fontSize: sizeNum + 'px'}"></div>
  </div>
</template>

<script type="text/ecmascript-6">
/* eslint-disable */
import WarterMark from '../../utils/warterMark';
export default {
  props: [],
  name: '',
  mounted() {
    WarterMark.set('法律文本', 'waterLaw');
  },
 data () {
    return {
      sizeNum: 14,
      text: ''
    }
 },
  methods: {
    setFontSize(num) {
      this.sizeNum = num;
    },
  }
};
</script>

<style scoped>
  .font-size{
    position: absolute;
    right: 4rem;
  }
  .large-font{
    font-size: 16px;
  }
  .med-font{
    font-size: 14px;
  }
  .small-font{
    font-size: 12px;
  }
  p{
    color: red !important;
  }
</style>

WarterMark.set('法律文本', 'waterLaw')中，‘法律文本’是要显示的水印内容，waterLaw是需要展示水印的容器id。

在项目中使用是放在created函数中的。

this.$nextTick(() => {
   setTimeout(() => {
     WarterMark.set(this.waterContent, 'waterLaw');
    }, 1000);
  });

其中：waterMark.js为：（可创建waterMark.js，直接复制后调用）

'use strict';
// 水印
let watermark = {};

let setWatermark = (str, domId) => {
  let id = '1.23452384164.123412415';

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

  let can = document.createElement('canvas');
  can.width = 320;
  can.height = 150;

  let cans = can.getContext('2d');
  cans.rotate(-10 * Math.PI / 180);
  cans.font = '20px Vedana';
  cans.fillStyle = 'rgba(200, 200, 200, 0.20)';
  cans.textAlign = 'left';
  cans.textBaseline = 'Middle';
  cans.fillText(str, can.width / 3, can.height / 2);

  let div = document.createElement('div');
  div.id = id;
  div.style.pointerEvents = 'none';
  div.style.top = '10rem';
  div.style.left = '10rem';
  div.style.right = '15rem';
  div.style.position = 'absolute';
  div.style.zIndex = '100000';
  // div.style.width = document.documentElement.clientWidth - 100 + 'px';
  div.style.width = 'unset';
  // div.style.height = document.documentElement.clientHeight - 100 + 'px';
  div.style.height = '76%';
  div.style.background = 'url(' + can.toDataURL('image/png') + ') left top repeat';
  // console.log(document.getElementById(domId));
  document.getElementById(domId).appendChild(div);
  return id;
};

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

export default watermark;