参考 https://blog.csdn.net/fdyshlk/article/details/78768078

public sealed class RectTransformUtility
{
	// 计算child在root中的区域位置
	public static Bounds CalculateRelativeRectTransformBounds(Transform root, Transform child);
	
	// 计算trans在直接父容器中的区域位置
	public static Bounds CalculateRelativeRectTransformBounds(Transform trans);
	
	/// <summary>
	// 交换rect的Width和Height值以及Pivot的X和Y值
	// recursive=true, 子对象的值也会发生交换
	// recursive=false, 只交换自己的值
	// keepPositioning=true, 保持rect的PosX和PosY不变,元素位置可变.
	// keepPositioning=false, 保持元素位置不变，rect的PosX和PosY可变.
	/// </summary>
	public static void FlipLayoutAxes(RectTransform rect, bool keepPositioning, bool recursive);
	
	/// <summary>
	// axis=0, 翻转Pivot的X值 (例如 X=0.4, 翻转后变为X=0.6)
	// axis=1, 翻转Pivot的Y值
	/// </summary>
	public static void FlipLayoutOnAxis(RectTransform rect, int axis, bool keepPositioning, bool recursive);
	
	// 使point对齐像素坐标
	public static Vector2 PixelAdjustPoint(Vector2 point, Transform elementTransform, Canvas canvas);
	
	// 使rectTransform的四个角对齐像素坐标
	public static Rect PixelAdjustRect(RectTransform rectTransform, Canvas canvas);
	
	// 判断screenPoint是否在rect区域内 (Render Mode=Screen Space - Overlay)
	public static bool RectangleContainsScreenPoint(RectTransform rect, Vector2 screenPoint);
	
	// 判断screenPoint是否在rect区域内 (cam为UI像机)
	public static bool RectangleContainsScreenPoint(RectTransform rect, Vector2 screenPoint, Camera cam);
	
	// 屏幕坐标转rect本地坐标
	public static bool ScreenPointToLocalPointInRectangle(RectTransform rect, Vector2 screenPoint, Camera cam, out Vector2 localPoint);
	
	// 从cam发出一条射线穿过screenPos点
	public static Ray ScreenPointToRay(Camera cam, Vector2 screenPos);
	
	// 屏幕坐标转世界坐标(相对于rect)，可理解为从screenPoint发出的射线与rect的交点。
	public static bool ScreenPointToWorldPointInRectangle(RectTransform rect, Vector2 screenPoint, Camera cam, out Vector3 worldPoint);
	
	// 世界坐标转屏幕坐标
	public static Vector2 WorldToScreenPoint(Camera cam, Vector3 worldPoint);
}