vue背景图片及背景纯色加水印

1、背景图片

在main.js写

Vue.prototype.drawAndShareImage = async (width, height, url, text, callback) => {
  var canvas = document.createElement('canvas')
  canvas.width = width
  canvas.height = height
  var context = canvas.getContext('2d')

  context.rect(0, 0, canvas.width, canvas.height)

  var myImage = new Image()
  myImage.src = url.replace(/ /g, '').replace(/"/g, '')
  myImage.crossOrigin = 'Anonymous'

  myImage.onload = () => {
    context.drawImage(myImage, 0, 0, width, height)
    let text1 = ''
    for (let i = 0; i < 30; i++) {
      text1 += (' ' + text)
    }
    for (let i = 0; i < 2000; i++) {
      context.rotate((-45 * Math.PI) / 180) // 水印初始偏转角度
      context.font = '20px microsoft yahei'
      context.fillStyle = 'rgba(255,255,255,0.15)'
      context.fillText(text1, -1000, i * 90)
      context.rotate((45 * Math.PI) / 180) // 把水印偏转角度调整为原来的，不然他会一直转
    }
    // varbase64=
    // dom.style.backgroundImage = 'url(\'' + base64 + '\')'
    callback(canvas.toDataURL('image/png'))
  }
}

在组件中调用

let img = document.getElementsByClassName('className')[0]
let style = img.currentStyle || window.getComputedStyle(img, false)
let bi = style.backgroundImage.replace('url(', '').replace(')', '')
this.drawAndShareImage(img.offsetWidth, img.offsetHeight, bi, '文字内容', (url) => {
  img.setAttribute('style', 'background:url("' + url + '")')
})

2、纯色背景水印

Vue.prototype.watchCanvs = (width, height, text, classname) => {
  let canvas = document.createElement('canvas')
  canvas.width = width
  canvas.height = height
  let context = canvas.getContext('2d')
  let text1 = ''
  for (let i = 0; i < 30; i++) {
    text1 += (' ' + text)
  }
  for (let i = 0; i < 2000; i++) {
    context.rotate((-45 * Math.PI) / 180) // 水印初始偏转角度
    context.font = '20px microsoft yahei'
    context.fillStyle = 'rgba(0,0,0,0.1)'
    context.fillText(text1, -1000, i * 90)
    context.rotate((45 * Math.PI) / 180) // 把水印偏转角度调整为原来的，不然他会一直转
  }

  // 生成base64格式的图片路径
  let curl = canvas.toDataURL('image/png')
  // 将图片作为背景样式插入
  classname.style.background =
    '#ffffff url(' + curl + ')'
}

在组件中调用

let div = document.getElementsByClassName('className')[0]
this.watchCanvs(div.offsetWidth, div.offsetHeight, '文字内容', div)