vue水印-第二种方法：通过指令

import Vue from ‘vue‘

Vue.directive(‘watermark‘, (el, binding) => {
  function addWaterMarker(str, parentNode, font, textColor) {
    // 水印文字，父元素，字体，文字颜色
    var can = document.createElement(‘canvas‘)
    parentNode.appendChild(can)
    can.width = 400
    can.height = 200
    can.style.display = ‘none‘
    var cans = can.getContext(‘2d‘)
    cans.rotate((-20 * Math.PI) / 180)
    cans.font = font || ‘16px Microsoft JhengHei‘
    cans.fillStyle = textColor || ‘rgba(180, 180, 180, 0.3)‘
    cans.textAlign = ‘left‘
    cans.textBaseline = ‘Middle‘
    cans.fillText(str, can.width / 3, can.height / 2)
    parentNode.style.backgroundImage = ‘url(‘ + can.toDataURL(‘image/png‘) + ‘)‘
  }
  addWaterMarker(
    binding.value.text,
    el,
    binding.value.font,
    binding.value.textColor
  )
})