生成动态海报，带二维码

前提：装插件html2canvas 、QRCode

<div class="dialog-content" id="posterHtml">
        <img :src="posterPageTemplate">
        <!-- 二维码 -->
        <div class="qrcode"><div id="qrcodeImg"></div></div>
        <p class="txt-center tips fs-24">长按图片识别二维码，立即申请！</p>
      </div>

<script>
import html2canvas from 'html2canvas'
import QRCode from 'qrcodejs2'
import utils from '@/components/utils'
export default {
  props: {
    visible: {
      type: Boolean,
      default: false
    }
  },
  data () {
    return {
      isShow: false,
      config: { // 二维码参数
        downloadFilename: '专属海报'
      },
      posterImg: '', // 最终生成的海报图片
      qrcode: '',
      qrcodeUrl: '', // 二维码链接
      posterPageTemplate: '' // 专属海报页背景图
    }
  },
  mounted () {
    this.getData()
  },
  methods: {
    imageUrlToBase64 (url) {
      // 一定要设置为let，不然图片不显示
      let image = new Image()

      // 解决跨域问题
      image.setAttribute('crossOrigin', 'anonymous')

      let imageUrl = url
      image.src = imageUrl

      // image.onload为异步加载
      image.onload = () => {
        let canvas = document.createElement('canvas')
        canvas.width = image.width
        canvas.height = image.height
        let context = canvas.getContext('2d')
        context.drawImage(image, 0, 0, image.width, image.height)

        let quality = 0.8
        // 这里的dataurl就是base64类型
        let dataURL = canvas.toDataURL('image/jpeg', quality)// 使用toDataUrl将图片转换成jpeg的格式,不要把图片压缩成png，因为压缩成png后base64的字符串可能比不转换前的长！
        this.posterPageTemplate = dataURL
        if (utils.isIOS && ('addEventListener' in document)) {
          this.$loading.show()
          console.log('ios设备')
          setTimeout(() => {
            this.showPoster()
          }, 1000)
        } else {
          console.log('android设备')
          this.showPoster()
        }
      }
    },
    // 关闭弹框
    closeDialog () {
      this.$emit('close')
      // 清除二维码
      this.qrcode.clear()
    },
    getData () {
      // posterImg 请求接口获取海报图片
      // 请求接口开始 ======
      let posterImg = ''
      this.imageUrlToBase64(posterImg)
    },
    createQrcode () {
      // 生成二维码
      const qrcodeImgEl = document.getElementById('qrcodeImg')
      qrcodeImgEl.innerHTML = ''
      this.qrcode = new QRCode(qrcodeImgEl, {
         105,
        height: 105,
        colorDark: '#000000',
        colorLight: '#ffffff',
        text: this.qrcodeUrl, // 设置二维码内容或跳转地址
        correctLevel: QRCode.CorrectLevel.H
      })
    },
    createPoster () {
      this.createQrcode()
      // 生成海报
      const _this = this
      const domObj = document.getElementById('posterHtml')
      html2canvas(domObj, {
        useCORS: true, // 允许图片跨域
        allowTaint: false,
        logging: false,
        letterRendering: false,
        scale: window.devicePixelRatio
      }).then((canvas) => {
        // 在微信里,可长按保存或转发
        _this.posterImg = canvas.toDataURL()
        // console.log(_this.posterImg)
      })
    },
    // 显示海报
    showPoster () {
      this.$nextTick(() => {
        this.createPoster()
        this.createQrcode()
      })
      this.$loading.hide()
      this.isShow = true
    }
  }
}
</script>