vue3 项目添加水印的实现方法

实现原理

通过在 canvas 上绘制出字体，设置好样式，然后以图片的样式导出，最后用图片作为水印层的背景图。

实现效果

全屏实现

实现方法

（1）在src下创建一个util文件夹，创建一个watermark.ts文件

export const getmark = () => {

  const setWatermark = (str: any) => {

    const id = "1.23452384164.123412416";

\


    if (document.getElementById(id) !== null) {

      document.body.removeChild(document.getElementById(id)!);

    }

\


    //创建一个画布

    const can = document.createElement("canvas");

    //设置画布的长宽

    can.width = 150;

    can.height = 120;

\


    const cans = can.getContext("2d")!;

    //旋转角度

    cans.rotate((-15 * Math.PI) / 180);

    cans.font = "18px 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";

    //在画布上绘制填色的文本（输出的文本，开始绘制文本的X坐标位置，开始绘制文本的Y坐标位置）

    cans.fillText(str, can.width / 8, can.height / 2);

\


    const div = document.createElement("div");

    div.id = id;

    div.style.pointerEvents = "none";

    div.style.top = "30px";

    div.style.left = "0px";

    div.style.position = "fixed";

    div.style.zIndex = "100000";

    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

  const watermark = (str: string) => {

    let id = setWatermark(str);

    setInterval(() => {

      if (document.getElementById(id) === null) {

        id = setWatermark(str);

      }

    }, 500);

    window.onresize = () => {

      setWatermark(str);

    };

  };

  return { watermark };

};

(2)设置水印:在需要水印的页面添加如下代码

<script setup lang="ts">
import {onMounted, onUnmounted, ref} from 'vue';
import { getmark } from "./util/watermark";

const { watermark } = getmark();
    onMounted(() => {
      watermark("你的名字");//水印名
    });

    onUnmounted(() => {
      watermark("");
    });
</script>

vue2 的使用方法基本相同，只需换为对应的生命周期即可。下面把相应代码也贴出来，供大家参考。

（1）项目中新建一个 watermark.js 文件

let watermark = {};

let setWatermark = (text, sourceBody) => {
  let id =
    Math.random() * 10000 +
    "-" +
    Math.random() * 10000 +
    "/" +
    Math.random() * 10000;

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

  let can = document.createElement("canvas");
  can.width = 120; //设置水印之间的左右间距
  can.height = 80; //设置水印之间的上下间距

  let cans = can.getContext("2d");
  cans.rotate((-20 * Math.PI) / 180);
  cans.font = "15px Vedana";
  cans.fillStyle = "rgba(0, 0, 0, .5)";
  cans.textAlign = "left";
  cans.textBaseline = "Middle";
  cans.fillText(text, can.width / 20, can.height);

  let water_div = document.createElement("div");
  water_div.id = id;
  water_div.className = "watermarkClass";
  water_div.style.pointerEvents = "none";
  water_div.style.background =
    "url(" + can.toDataURL("image/png") + ") left top repeat";
  if (sourceBody) {
    water_div.style.width = "100%";
    water_div.style.height = "100%";
    sourceBody.appendChild(water_div);
  } else {
    water_div.style.top = "3px";
    water_div.style.left = "0px";
    water_div.style.position = "fixed";
    water_div.style.zIndex = "100000";
    water_div.style.width = document.documentElement.clientWidth + "px";
    water_div.style.height = document.documentElement.clientHeight + "px";
    document.body.appendChild(water_div);
  }

  return id;
};

/**
 *  该方法只允许调用一次
 *  @param:
 *  @text == 水印内容
 *  @sourceBody == 水印添加的位置，不传就是body
 * */
watermark.set = (text, sourceBody) => {
  const domArr = Array.from(document.getElementsByClassName("watermarkClass"));
  for (let i = 0; i < domArr.length; i++) {
    const element = domArr[i];
    // element.parentNode.removeChild(element);
    element.remove();
  }
  if (text == "") {
    return;
  }
  setWatermark(text, sourceBody);
  // let id = setWatermark(text, sourceBody);
  // setInterval(() => {
  //   if (document.getElementById(id) === null) {
  //     id = setWatermark(text, sourceBody);
  //   }
  // }, 2000);
  // window.onresize = () => {
  //   setWatermark(text, sourceBody);
  // };
};

export default watermark;

(2)main.js 中引入 watermark.js

// 引入水印文件地址
import watermark from './util/watermark.js'
Vue.prototype.$watermark = watermark

(3)全屏水印

<template>
  <div class="page">
  </div>
</template>

<script>
export default {
  data() {
    return {};
  },
  mounted(){
    this.$watermark.set("水印")
  },
  beforeDestroy() {
    this.$watermark.set("");
  }
};
</script>

<style scoped>
.page{
  width: 100%;
  height: 100%;
  background-color: skyblue;
}
</style>

局部水印：

<template>
  <div class="page">
    <div ref="content" style="width: 500px;height: 500px;border: 2px solid red;"></div>
  </div>
</template>

<script>
export default {
  data() {
    return {};
  },
  mounted(){
    this.$watermark.set("水印",this.$refs.content)
  },
  beforeDestroy() {
    this.$watermark.set("",this.$refs.content);
  }
};
</script>

<style scoped>
.page{
  width: 100%;
  height: 100%;
  background-color: skyblue;
}
</style>