如何在Unity编辑器窗口中正确绘制预览缩略图？

using UnityEditor;
using UnityEngine;

public class ThumbnailWindow : EditorWindow
{
    private Texture2D thumbnail;

    [MenuItem("Window/Thumbnail Window")]
    private static void OpenWindow()
    {
        ThumbnailWindow window = GetWindow<ThumbnailWindow>();
        window.titleContent = new GUIContent("Thumbnail Window");
        window.Show();
    }

    private void OnGUI()
    {
        EditorGUILayout.LabelField("Preview Thumbnail");

        if (thumbnail != null)
        {
            Rect thumbnailRect = GUILayoutUtility.GetRect(128, 128);
            EditorGUI.DrawPreviewTexture(thumbnailRect, thumbnail);
        }

        if (GUILayout.Button("Load Thumbnail"))
        {
            LoadThumbnail();
        }
    }

    private void LoadThumbnail()
    {
        // 在这里加载预览缩略图的Texture对象
        // 例如：thumbnail = AssetDatabase.LoadAssetAtPath<Texture2D>("Assets/Textures/Thumbnail.png");
    }
}