水印图例

1.新建Watermark.js 文件

const watermark = {}

const setWatermark = (text, sourceBody) => {
  const id =
    Math.random() * 10000 +
    '-' +
    Math.random() * 10000 +
    '/' +
    Math.random() * 10000

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

  const can = document.createElement('canvas')
  can.width = 200 // 设置水印之间的左右间距
  can.height = 150 // 设置水印之间的上下间距

  const cans = can.getContext('2d')
  cans.rotate((-20 * Math.PI) / 180)
  cans.font = '15px Vedana'
  cans.fillStyle = 'rgba(0, 0, 0, .3)'  //水印颜色
  cans.textAlign = 'left'
  cans.textBaseline = 'Middle'
  cans.fillText(text, can.width / 20, can.height)

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

  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. 在vue 文件使用

<script>
import Watermark from './Watermark'  //引入水印文件
export default {
  name: 'app',
  mounted () {
    Watermark.set(水印名称)// 添加水印名称
  }
}
</script>

<style>

</style>