如何利用Layui实现可拖拽的图片裁剪功能

<link rel="stylesheet" href="https://cdn.staticfile.org/layui/2.5.6/css/layui.css">
<script src="https://cdn.staticfile.org/layui/2.5.6/layui.js"></script>

<div class="demo" style="margin:20px;">
  <div class="layui-upload">
    <button type="button" class="layui-btn" id="upload">上传图片</button>
    <button type="button" class="layui-btn" id="cut">裁剪图片</button>
  </div>
  <div class="layui-upload-img" id="image-container"></div>
  <div class="layui-row layui-col-space10" id="crop-container"></div>
</div>

layui.use('upload', function(){
  var upload = layui.upload;

  //执行实例
  var uploadInst = upload.render({
    elem: '#upload',
    url: '/upload/',
    done: function(res){
      //上传完毕回调
      if(res.code == 0){
        //显示图片
        $("#image-container").html('<img src="' + res.data.src + '" class="layui-upload-img">');
        //裁剪图片
        initCrop(res.data.src);
      }
    }
  });
});

//初始化裁剪框
function initCrop(src) {
  layui.use(['slider', 'cropper'], function(){
    var slider = layui.slider, cropper = layui.cropper;

    //添加裁剪框
    $("#crop-container").html('<div id="crop"></div>');

    //创建实例
    var cropperInst = cropper.render({
      elem: '#crop',
      imgSrc: src,
      area: ['400px', '400px'],
      done: function(res){
        //裁剪完毕回调
        console.log(res);
      }
    });
  });
}

//裁剪图片
function cropImage() {
  layui.use('cropper', function(){
    var cropper = layui.cropper;
    //获取裁剪结果
    var result = cropper.getData('#crop');
    console.log(result);
  });
}

.demo {
  width: 600px;
}

.layui-upload {
  margin-bottom: 10px;
}

.layui-upload-img {
  margin: 10px 0;
}

#crop {
  margin-top: 10px;
}