<camera mode="normal" device-position="{{cardPosition}}" flash="off" style="height:{{ cameraHeight-60 }}px">
    <cover-view class="controls" style="width: 100%;height: 100%;">
      <!-- 头像面 -->
      <cover-image wx:if="{{cardType == 1}}" class="icon-w569-h828" src="/images/icon/take_idcard_a.png" />
      <!-- 国徽面 -->
      <cover-image wx:elif="{{cardType == 2}}" class="icon-w569-h828" src="/images/icon/take_idcard_b.png" />
      <!-- 免冠照 -->
      <cover-image wx:else class="icon-w569-h828" src="https://img-blog.csdnimg.cn/20210126144317636.png" />
    </cover-view>
  </camera>
Component({
properties: {
    cardType: String,
  },
  observers:{
    'cardType':function(e){
      const that = this;
      if(e == 1 || e == 2){
        that.setData({
          cardPosition:'back'
        })
      }else{
        that.setData({
          cardPosition:'front'
        })
      }
    }
  },
  data: {
    cameraHeight: wx.getSystemInfoSync().windowHeight,
    cameraWidth: wx.getSystemInfoSync().windowWidth,
    hide: true,
    cardPosition:'back',
    myCanvas1_canvas: '',
    myCanvas1_ctx: '',
  },
  ......
});