unity 实现图片的放大与缩小（根据鼠标位置拉伸放缩）

1创建UnityHelper.cs

using UnityEngine.Events;
using UnityEngine.EventSystems;

public class UnityHelper
{
    /// <summary>
    /// 简化向EventTrigger组件添加事件的操作。
    /// </summary>
    /// <param name="_eventTrigger">要添加事件监听的UI元素上的组件。
    /// <param name="_eventType">监听事件类型</param>
    /// <param name="_unityAction">监听事件触发的函数</param>
    public static void EventTriggerAddEvent(EventTrigger _eventTrigger, EventTriggerType _eventType, UnityAction<BaseEventData> _unityAction)
    {                         
        if (_eventTrigger == null)
        {
            return;
        }
        //创建一个新的UnityAction<BaseEventData>委托实例，指向传入的_unityAction
        UnityAction<BaseEventData> action = new UnityAction<BaseEventData>(_unityAction);
        //检查_eventTrigger的triggers列表是否已包含事件。如果有，遍历这些事件，寻找匹配_eventType的事件。
        //如果找到匹配项，则直接将_unityAction添加到该事件的回调列表中并返回，避免重复添加
        if (_eventTrigger.triggers.Count != 0)
        {
            for (int i = 0; i < _eventTrigger.triggers.Count; i++)
            {
                if (_eventTrigger.triggers[i].eventID == _eventType)
                {
                    _eventTrigger.triggers[i].callback.AddListener(_unityAction);
                    return;
                }
            }
        }
        //如果没有找到匹配的事件类型，则创建一个新的EventTrigger.Entry对象，设置其eventID为_eventType，
        //并将之前创建的委托添加到其callback中，最后将这个新事件条目添加到_eventTrigger的triggers列表里。
        //定义所要绑定的事件类型
        EventTrigger.Entry entry = new EventTrigger.Entry();
        //设置事件类型
        entry.eventID = _eventType;
        //设置回掉函数
        entry.callback.AddListener(action);
        //添加触发事件到EventTrigger组件上
        _eventTrigger.triggers.Add(entry);
    }
}

2.新建下列代码后组件绑定与配置

using System;
using UnityEngine;
using UnityEngine.EventSystems;
//拖动调整ui大小

public class ComponentBoxPoint : MonoBehaviour, IDragHandler
{
    public enum BoxPoint // 不同的拖拽点
    {
        UpperLeft,
        UpperCenter,
        UpperRight,
        MiddleLeft,
        MiddleRight,
        LowerLeft,
        LowerCenter,
        LowerRight,
    }

    public BoxPoint boxPoint;//当前拖拽点类型
    public Texture2D cursorTexture;//鼠标悬停时显示的自定义光标纹理
    private RectTransform componentRectTransform;//父级UI组件的RectTransform，用于调整大小和位置
    private Vector2 lastPosition;//父级的x,y坐标
    private EventTrigger eventTrigger;
    private bool isDragging = false;
    private CJCE_Component cjce_component;//父级组件，用于通信是否正在拖动状态。
    //public bool limitHorizontalAxis;//限制拖动时的轴向移动。
    //public bool limitVerticalAxis;
    public Action<ComponentBoxPoint> draggingEvent;//拖动委托事件
    public Action<ComponentBoxPoint> onPointerDownEvent;//按下
    public Action<ComponentBoxPoint> onPointerUpEvent;//松开
    public Vector2 dragOffset;//拖动偏移量

    //坐标系转换成一致的坐标系
    private Camera panelCamera; // 渲染拖拽物体所在的Canvas的相机

    //canvas渲染方式：Screen Space - Overlay—>像素；Screen Space - Camera或World Space—>世界坐标系统，通常以米为单位
    //private Canvas uiCanvas; // 脚本所挂载对象所在的Canvas

    private float scalex;//获取Canvas的缩放
    private float scaley;

    private float posX;//父对象的世界坐标
    private float posY;

    private float width;//父对象的宽度和高度
    private float height;

    private void Start()
    {
        Init();
        InitUIEvent();
    }

    private void Init()
    {
        componentRectTransform = this.transform.parent.GetComponent<RectTransform>();
        lastPosition = componentRectTransform.position;//世界坐标
        eventTrigger = this.GetComponent<EventTrigger>();
        cjce_component = this.GetComponentInParent<CJCE_Component>();

        // 寻找带有"PanelCamera"标签的相机
        GameObject cameraObj = GameObject.FindGameObjectWithTag("tagname");
        if (cameraObj != null)
        {
            panelCamera = cameraObj.GetComponent<Camera>();
        }

        // 寻找带有"PPT"标签的Canvas
        GameObject canvasObj = GameObject.FindGameObjectWithTag("tagname");
        Transform transformComponent = canvasObj.GetComponent<Transform>();
        Vector3 scale = transformComponent.localScale;//缩放比例
        scalex = scale.x;
        scaley = scale.y;

    }
    private void InitUIEvent()//添加事件监听
    {
        UnityHelper.EventTriggerAddEvent(eventTrigger, EventTriggerType.PointerEnter, OnPointerEnter);
        UnityHelper.EventTriggerAddEvent(eventTrigger, EventTriggerType.PointerDown, OnPointerDown);
        UnityHelper.EventTriggerAddEvent(eventTrigger, EventTriggerType.PointerUp, OnPointerUp);
        UnityHelper.EventTriggerAddEvent(eventTrigger, EventTriggerType.PointerExit, OnPointerExit);
    }

    public void OnPointerEnter(BaseEventData eventData)//进入
    {
        Cursor.SetCursor(cursorTexture, new Vector2(cursorTexture.width / 2F, cursorTexture.height / 2f), CursorMode.Auto);
    }
    public void OnPointerDown(BaseEventData eventData)//按下
    {
        Cursor.SetCursor(cursorTexture, new Vector2(cursorTexture.width / 2F, cursorTexture.height / 2f), CursorMode.Auto);
        isDragging = true;
        if (cjce_component) { cjce_component.boxPointIsDraggin = isDragging; }
        if (onPointerDownEvent != null)
        {
            onPointerDownEvent(this);
        }
        lastPosition = componentRectTransform.position;
        posX = lastPosition.x;
        posY = lastPosition.y;
        width = componentRectTransform.rect.width;
        height = componentRectTransform.rect.height;
    }
    public void OnDrag(PointerEventData eventData)//拖拽
    {

        Vector3 mousePosition = Input.mousePosition;//屏幕坐标系：左下角原点，像素为单位
        mousePosition.z = panelCamera.nearClipPlane;
        Vector3 worldMousePosition = panelCamera.ScreenToWorldPoint(mousePosition);//坐标系转换
        float mouseX = worldMousePosition.x;
        float mouseY = worldMousePosition.y;



        //Vector2 _offset = eventData.delta;
        //if (limitHorizontalAxis)
        //{
        //    _offset.x = 0;
        //}
        //if (limitVerticalAxis)
        //{
        //    _offset.y = 0;
        //}
        //dragOffset = _offset;
        switch (boxPoint)
        {
            case BoxPoint.UpperLeft:
                componentRectTransform.position = new Vector3(mouseX, mouseY, 0);
                componentRectTransform.sizeDelta = new Vector2((-mouseX + posX) / scalex + width, (mouseY - posY) / scaley + height);
                break;
            case BoxPoint.UpperCenter:
                componentRectTransform.position = new Vector3(posX, mouseY, 0);
                componentRectTransform.sizeDelta = new Vector2(width, (mouseY - posY) / scaley + height);
                break;
            case BoxPoint.UpperRight:
                componentRectTransform.position = new Vector3(posX, posY + (mouseY - posY), 0);
                componentRectTransform.sizeDelta = new Vector2((mouseX - posX) / scalex, (mouseY - posY) / scaley + height);
                break;
            case BoxPoint.MiddleLeft:
                componentRectTransform.position = new Vector3(mouseX, posY, 0);
                componentRectTransform.sizeDelta = new Vector2((-mouseX + posX) / scalex + width, height);
                break;
            case BoxPoint.MiddleRight:
                componentRectTransform.sizeDelta = new Vector2((mouseX - posX) / scalex, height);
                break;
            case BoxPoint.LowerLeft:
                componentRectTransform.position = new Vector3(mouseX, posY, 0);
                componentRectTransform.sizeDelta = new Vector2((-mouseX + posX) / scalex + width, (-mouseY + posY) / scaley);
                break;
            case BoxPoint.LowerCenter:
                componentRectTransform.sizeDelta = new Vector2(width, (-mouseY + posY) / scaley);
                break;
            case BoxPoint.LowerRight:
                componentRectTransform.sizeDelta = new Vector2((mouseX - posX) / scalex, (-mouseY + posY) / scaley);
                break;
            default:
                break;
        }
        if (draggingEvent != null)
        {
            draggingEvent(this);
        }
    }
    public void OnPointerUp(BaseEventData eventData)//释放
    {
        Cursor.SetCursor(null, Vector2.zero, CursorMode.Auto);
        isDragging = false;
        if (cjce_component) { cjce_component.boxPointIsDraggin = isDragging; }
        if (onPointerUpEvent != null)
        {
            onPointerUpEvent(this);
        }

        //更新位置信息
        lastPosition = componentRectTransform.position;
        posX = lastPosition.x;
        posY = lastPosition.y;
        width = componentRectTransform.rect.width;
        height = componentRectTransform.rect.height;

    }
    public void OnPointerExit(BaseEventData eventData)//离开
    {
        if (isDragging)
        {
            return;
        }
        Cursor.SetCursor(null, Vector2.zero, CursorMode.Auto);//恢复光标状态
    }


}