<camera device-position="back"  
        flash="off"
        binderror="error"
        style="width:100%;height:300px;" 
        frame-size="medium" 
        style="width: 750rpx; height: 331rpx;
                 display: block; box-sizing: border-box; 
                 left: 0rpx; top: 0rpx" 
          mode="scanCode" 
          resolution="high"></camera>