效果展示：

步骤流程：

1.使用的是UGUI，将下面的脚本拖拽到图片上即可。

using UnityEngine;
using UnityEngine.UI;
using UnityEngine.EventSystems;

public class CheckImage : MonoBehaviour, IDragHandler, IBeginDragHandler, IEndDragHandler, IPointerEnterHandler, IPointerExitHandler
{
    public float MaxRange = 5f;
    public float MinRange = 0.5f;
    private Vector3 offPos;
    private Vector3 arragedPos;
    private bool isEnter = false;
    private bool isDrag = false;

    void Update()
    {
        if (!isEnter) return;
        if (!isDrag)
        {
            SetPivotAndPos();
            if (Input.GetAxis("Mouse ScrollWheel") > 0)
            {
                transform.localScale += (transform.localScale.x >= MaxRange ? Vector3.zero : Vector3.one * 0.1f);
            }
            else if (Input.GetAxis("Mouse ScrollWheel") < 0)
            {
                transform.localScale -= (transform.localScale.x <= MinRange ? Vector3.zero : Vector3.one * 0.1f);
            }
        }
    }

    public void OnBeginDrag(PointerEventData eventData)
    {
        isDrag = true;
        if (RectTransformUtility.ScreenPointToWorldPointInRectangle(transform.GetComponent<RectTransform>(), Input.mousePosition, null, out arragedPos))
        {
            offPos = transform.position - arragedPos;
        }
    }

    public void OnDrag(PointerEventData eventData)
    {
        transform.position = offPos + Input.mousePosition;
    }

    public void OnEndDrag(PointerEventData eventData)
    {
        transform.position = offPos + Input.mousePosition;
        isDrag = false;
    }

    public void OnPointerEnter(PointerEventData eventData)
    {
        isEnter = true;
    }

    public void OnPointerExit(PointerEventData eventData)
    {
        isEnter = false;
    }

    private void SetPivotAndPos()
    {
        float OffsetX = Input.mousePosition.x - transform.position.x;
        float OffsetY = Input.mousePosition.y - transform.position.y;

        float PivotX = OffsetX / transform.GetComponent<RectTransform>().rect.width / transform.localScale.x;
        float PivotY = OffsetY / transform.GetComponent<RectTransform>().rect.height / transform.localScale.y;

        transform.GetComponent<RectTransform>().pivot += new Vector2(PivotX, PivotY);
        transform.localPosition += new Vector3(OffsetX, OffsetY, 0);
    }
}

2.再给图片的父物体添加个Mask遮罩就ok了。