UGUI 不規則碰撞檢測，支持不規則碰撞區域編輯

using UnityEngine;
using UnityEngine.UI;

[RequireComponent(typeof(PolygonCollider2D))]
public class PolygonImage : Image
{
    private PolygonCollider2D mCollider;
    protected override void Awake()
    {
        base.Awake();
        mCollider = GetComponent<PolygonCollider2D>();
    }

    public override bool IsRaycastLocationValid(Vector2 sp, Camera eventCamera)
    {
        return ContainsPoint(mCollider.points, sp);
    }

    bool ContainsPoint(Vector2[] polyPoints, Vector2 p)
    {
        int j = polyPoints.Length - 1;
        bool inside = false;
        for (int i = 0; i < polyPoints.Length; j = i++)
        {
            polyPoints[i].x += transform.position.x;
            polyPoints[i].y += transform.position.y;
            if (((polyPoints[i].y <= p.y && p.y < polyPoints[j].y) || (polyPoints[j].y <= p.y && p.y < polyPoints[i].y)) && (p.x < (polyPoints[j].x - polyPoints[i].x) * (p.y - polyPoints[i].y) / (polyPoints[j].y - polyPoints[i].y) + polyPoints[i].x))
                inside = !inside;
        }
        return inside;
    }
}