using UnityEngine;
using UnityEngine.UI;

[RequireComponent(typeof(RawImage))]
public class MaintainAspectRatio : MonoBehaviour
{
    //None: 不调整图片大小，使用原始大小。
    //FitInParent: 按比例缩放图片以适应固定尺寸的框。
    //EnvelopeParent: 按比例缩放图片以覆盖固定尺寸的框。
    public enum AspectMode
    {
        None,
        FitInParent,
        EnvelopeParent
    }

    public AspectMode aspectMode = AspectMode.None;
    private RawImage rawImage;
    private RectTransform parentRectTransform;

    void Start()
    {
        rawImage = GetComponent<RawImage>();
        parentRectTransform = transform.parent.GetComponent<RectTransform>();
        //AdjustSize();
    }

    void Update()
    {
        // 在每帧更新时检查并调整大小
        //AdjustSize();
    }

    public void AdjustSize()
    {
        if (parentRectTransform == null) return;

        if (rawImage.texture == null) return;

        Vector2 fixedSize = parentRectTransform.rect.size;
        float imageAspect = (float)rawImage.texture.width / rawImage.texture.height;
        float targetAspect = fixedSize.x / fixedSize.y;

        RectTransform rt = rawImage.GetComponent<RectTransform>();

        switch (aspectMode)
        {
            case AspectMode.FitInParent:
                if (imageAspect > targetAspect)
                {
                    // 图片更宽
                    rt.SetSizeWithCurrentAnchors(RectTransform.Axis.Horizontal, fixedSize.x);
                    rt.SetSizeWithCurrentAnchors(RectTransform.Axis.Vertical, fixedSize.x / imageAspect);
                }
                else
                {
                    // 图片更高
                    rt.SetSizeWithCurrentAnchors(RectTransform.Axis.Vertical, fixedSize.y);
                    rt.SetSizeWithCurrentAnchors(RectTransform.Axis.Horizontal, fixedSize.y * imageAspect);
                }
                break;

            case AspectMode.EnvelopeParent:
                if (imageAspect > targetAspect)
                {
                    // 图片更宽
                    rt.SetSizeWithCurrentAnchors(RectTransform.Axis.Vertical, fixedSize.y);
                    rt.SetSizeWithCurrentAnchors(RectTransform.Axis.Horizontal, fixedSize.y * imageAspect);
                }
                else
                {
                    // 图片更高
                    rt.SetSizeWithCurrentAnchors(RectTransform.Axis.Horizontal, fixedSize.x);
                    rt.SetSizeWithCurrentAnchors(RectTransform.Axis.Vertical, fixedSize.x / imageAspect);
                }
                break;

            case AspectMode.None:
            default:
                // 原始图片大小
                rt.SetSizeWithCurrentAnchors(RectTransform.Axis.Horizontal, rawImage.texture.width);
                rt.SetSizeWithCurrentAnchors(RectTransform.Axis.Vertical, rawImage.texture.height);
                break;
        }
    }
}