unity中 限定UI的移动范围

前言：在最近项目中需要做一个功能，对image可进行放大缩小，移动，放大缩小，移动都比较简单，难点在于限定image的移动范围

 
 //image控件四个角的点坐标
 Vector3[] m_corners = new Vector3[4]；

  void CamereControl()
    {
        Camera camera = Camera.main.GetComponent<Camera>();
        if (camera)
        {
            if (!camera.pixelRect.Contains(Input.mousePosition))
            {
                return;
            }
        }
        m_bookImageRect.localScale = new Vector3(Mathf.Clamp(m_bookImageRect.localScale.x + Input.GetAxis("Mouse ScrollWheel"), 1, 5), Mathf.Clamp(m_bookImageRect.localScale.y + Input.GetAxis("Mouse ScrollWheel"), 1, 5), m_bookImageRect.localScale.z);

        if (Input.GetMouseButtonUp(1))
        {
            Cursor.SetCursor(null, Vector2.zero, CursorMode.Auto);
        }

        if (Input.GetMouseButton(1))
        {
            Cursor.SetCursor(m_cursorTexture, new Vector2(16,16), CursorMode.Auto);
            float m_x = Input.GetAxis("Mouse X");
            float m_y = Input.GetAxis("Mouse Y");
            Vector3 m_moveOffset = new Vector3(m_x, m_y, 0);
            Vector3 m_tempPos = m_bookImageRect.position;
            m_bookImageRect.position += m_moveOffset * Time.deltaTime * m_keySpeed * m_bookImageRect.localScale.x;
            m_customBook.GetWorldCorners(m_corners);
            if (m_corners[0].x > Screen.currentResolution.width - m_borderLineDis || m_corners[0].y > Screen.currentResolution.height - m_borderLineDis)
            {
                m_bookImageRect.position = m_tempPos;
            }
            if (m_corners[1].x > Screen.currentResolution.width - m_borderLineDis || m_corners[1].y < 0 + m_borderLineDis)
            {
                m_bookImageRect.position = m_tempPos;
            }
            if (m_corners[2].x < 0 + m_borderLineDis || m_corners[2].y < 0 + m_borderLineDis)
            {
                m_bookImageRect.position = m_tempPos;
            }
            if (m_corners[3].x < 0 + m_borderLineDis || m_corners[3].y > Screen.currentResolution.height - m_borderLineDis)
            {
                m_bookImageRect.position = m_tempPos;
            }


        }
        if (Input.GetMouseButton(2))
        {
            m_bookImageRect.position = GameObject.Find("MainUI").transform.position;
        }
    }