<textarea name="contents" id="editor1" rows="50" cols="90"></textarea>
  
  <script>
    // Replace the <textarea id="editor1"> with a CKEditor
    // instance, using default configuration.
    CKEDITOR.replace( 'editor1',{
  filebrowserUploadUrl: '파일업로드를 처리할 컨트롤러명/upload_receive_from_ck'
 });
  </script>

public function upload_receive_from_ck() 
 {  
  $config['upload_path'] = '이미지파일 저장 경로';
  $config['allowed_types'] = 'gif|jpg|png';
  $config['max_size'] = '1024';
  $config['max_width']  = '1024';
  $config['max_height']  = '768';
  $config['encrypt_name'] = TRUE;

  $this->load->library('upload', $config);

  if( ! $this->upload->do_upload("upload"))
  {
   $this->load->helper('alert');
   $error = $this->upload->display_errors('','');
   alert_only($error);
  }
  else
  {
   $CKEditorFuncNum = $this->input->get('CKEditorFuncNum');

   $data = $this->upload->data();
   $filename = $data['file_name'];

   $url = '이미지파일 저장경로'.$filename;

   echo "<script type='text/javascript'>window.parent.CKEDITOR.tools.callFunction('".$CKEditorFuncNum."', '".$url."', '전송에 성공 했습니다')</script>";
  }
 }

<script> 
  //<!CDATA[
  $(document).ready(function(){  
   CKEDITOR.on('dialogDefinition', function(ev) {
    var dialogName = ev.data.name;
    var dialogDefinition = ev.data.definition;

    if(dialogName == 'image') {
     var uploadTab = dialogDefinition.getContents('Upload');

     for (var i =0; i < uploadTab.elements.length; i++)
     {
      var el = uploadTab.elements[i];
      if(el.type != 'fileButton') {
       continue;
      }

      var onClick = el.onClick;

      el.onClick = function(evt){
       var dialog = this.getDialog();
       var fb = dialog.getContentElement(this['for'][0], this['for'][1]);
       var action = fb.getAction();
       var editor = dialog.getParentEditor();
       editor._.filebrowserSe = this;

       $(fb.getInputElement().getParent().$).append('<input type="hidden" name="<?= $this->security->get_csrf_token_name() ?>" value="<?= $this->security->get_csrf_hash() ?>" />');

       if(onClick && onClick.call(evt.sender, evt) === false) {
        return false;
       }
       return true;
      };
     }
    }
   }); 
  }); 
  //}}>
</script>