// 裁剪名片
  cropCard() {    
    let self = this;
    // 獲取dom結構
    let card_target = this.refs.copyCardArea; 
    domtoimage.toPng(card_target).then(function(dataUrl) {
      //andriod 
      if (dataUrl != "error") {
        // alert("domtoimage");
        self.setState({
          imgUrl: dataUrl,
          isDownloadImg: true,
        })
      }
      // ios
      else {
        let b64;
        html2canvas(card_target, {
          useCORS: true
        }).then(function(canvas) {
          try {
            b64 = canvas.toDataURL("image/png");
          } catch (err) {
            console.log(err)
              // alert(err)
          }
          self.setState({
            imgUrl: b64,
            isDownloadImg: true,
          })
        }).catch(function onRejected(error) {});
      }
    });
  }