unity 鼠标拖动UI 滚轮缩放大小

using System;
using System.Collections;
using System.Collections.Generic;
using UnityEngine;
using UnityEngine.EventSystems;
using UnityEngine.UI;
/// 
/// 鼠标拖动UI  滚轮缩放大小
/// 

public class PageDragToZoom : MonoBehaviour, IPointerExitHandler, IPointerEnterHandler, IBeginDragHandler, IDragHandler
{
    /// 
    /// 缩放速度
    /// 
    private float wheelSpeed = 0.1f;
    /// 
    /// 是否缩放（鼠标进入退出 判断）
    /// 
    public bool isTrue;

    Vector3 _originScale;//初始大小
    Vector3 _originPoint;//初始位置
    public Button _closeButton;//复位

    Vector3 offPos;
    Vector3 arragedPos;

    //Vector3 _scaleOne;
    //public Transform _ThisTransform;
    void Start()
    {
        _originPoint = this.transform.position;
        _originScale = this.transform.localScale;
        _closeButton.onClick.AddListener(CloseImage);
        //_scaleOne = transform.localScale;
    }
    
    void Update()
    {
        //UI最大可以放到两倍
        if (transform.localScale.x >= 2 || transform.localScale.x >= 2)
        {
            transform.localScale = new Vector3(2, 2, 2);
        }
        //UI最小可以缩小两倍
        if (transform.localScale.x