js watermark实现水印效果

1.创建watermark.js文件：

import id from "element-ui/src/locale/lang/id";

let watermark = {}
let setWatermark = (str) => {
  let id = '1.23452384164.123412415'
  if (document.getElementById(id) !== null) {
    document.body.removeChild(document.getElementById(id))
  }
 
  let can = document.createElement('canvas')
  can.width = 500
  can.height = 250
 
  let cans = can.getContext('2d')
  cans.rotate(-20 * Math.PI / 180)
  cans.font = '14px Microsoft JhengHei'
  cans.fillStyle = '#dddddd'
  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 = '70px'
  div.style.left = '0px'
  div.style.position = 'fixed'
  div.style.width = document.documentElement.clientWidth - 100 + 'px'
  div.style.height = document.documentElement.clientHeight - 100 + '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 = (str) => {
  let id = setWatermark(str)
  setInterval(() => {
    if (document.getElementById(id) === null) {
      id = setWatermark(str)
    }
  }, 500)
  window.onresize = () => {
    setWatermark(str)
  }
}
export default watermark

2.在需要的相关页面引入：

<script>
import watermark from '@/watermark.js'
export default{
   data(){
     return{}
   },
   mounted(){
     watermark.set('水印 水印 水印')//添加水印
   },
   destroyed(){
     watermark.set('')//去除水印
  }  
  }
</script>