Question `AssetPreview.GetMiniThumbnail` returns Prefab icon, not the prefab image shown in Project window.

Hello, I was wondering why `AssetPreview.GetMiniThumbnail` is not giving me the same images of prefabs as the project window?

I am using the code below to save prafab thumbnails under a specific directory.

Code (CSharp):

1.  
2. using UnityEngine;
3. using UnityEditor;
4. using System.Collections;
5. using System.Collections.Generic;
6. using System.IO;
7.  
8. public class PointThumbnailGenerator : EditorWindow
9. {
10.     UnityEngine.Object searchDirectory;
11.     List<GameObject> objList = new List<GameObject>();
12.     string dirPath = "Assets/Captures/"; // output dir
13.     int width = 100; // image width
14.     int height = 100; // image hegiht
15.  
16.     [MenuItem("Window/PointThumbnailGenerator")]
17.     static void ShowWindow()
18.     {
19.         GetWindow(typeof(PointThumbnailGenerator));
20.     }
21.  
22.     void OnGUI()
23.     {
24.         GUILayout.BeginHorizontal();
25.         GUILayout.Label("Search Directory : ", GUILayout.Width(110));
26.         searchDirectory = EditorGUILayout.ObjectField(searchDirectory, typeof(UnityEngine.Object), true);
27.         GUILayout.EndHorizontal();
28.         EditorGUILayout.Space();
29.  
30.         GUILayout.BeginHorizontal();
31.         GUILayout.Label("Save directory : ", GUILayout.Width(110));
32.         dirPath = EditorGUILayout.TextField(dirPath);
33.         GUILayout.EndHorizontal();
34.         EditorGUILayout.Space();
35.  
36.         GUILayout.BeginHorizontal();
37.         GUILayout.Label("Width : ", GUILayout.Width(110));
38.         width = EditorGUILayout.IntField(width);
39.         GUILayout.EndHorizontal();
40.         EditorGUILayout.Space();
41.  
42.         GUILayout.BeginHorizontal();
43.         GUILayout.Label("Height : ", GUILayout.Width(110));
44.         height = EditorGUILayout.IntField(height);
45.         GUILayout.EndHorizontal();
46.         EditorGUILayout.Space();
47.  
48.         if (GUILayout.Button(new GUIContent("Capture")))
49.         {
50.             if (searchDirectory == null) return;
51.  
52.             if (!Directory.Exists(dirPath))
53.             {
54.                 Directory.CreateDirectory(dirPath);
55.             }
56.  
57.             objList.Clear();
58.  
59.             string replaceDirectoryPath = AssetDatabase.GetAssetPath(searchDirectory);
60.             string[] filePaths = Directory.GetFiles(replaceDirectoryPath, "*.*");
61.             foreach (string filePath in filePaths)
62.             {
63.                 GameObject obj = AssetDatabase.LoadAssetAtPath(filePath, typeof(GameObject)) as GameObject;
64.                 if (obj != null)
65.                 {
66.                     objList.Add(obj);
67.                 }
68.             }
69.  
70.             foreach (GameObject obj in objList)
71.             {
72.                 Debug.Log("OBJ :  " + obj.name);
73.                 Capture(obj);
74.             }
75.         }
76.     }
77.  
78.     void Capture(GameObject obj)
79.     {
80.         Texture2D thumbnail = AssetPreview.GetMiniThumbnail(obj);
81.         if (thumbnail != null)
82.         {
83.             // Create a new readable texture and set its pixels from the existing texture
84.             Texture2D readableTexture = new Texture2D(thumbnail.width, thumbnail.height);
85.             RenderTexture rt = RenderTexture.GetTemporary(thumbnail.width, thumbnail.height);
86.             Graphics.Blit(thumbnail, rt);
87.             RenderTexture previous = RenderTexture.active;
88.             RenderTexture.active = rt;
89.             readableTexture.ReadPixels(new Rect(0, 0, rt.width, rt.height), 0, 0);
90.             readableTexture.Apply();
91.             RenderTexture.active = previous;
92.             RenderTexture.ReleaseTemporary(rt);
93.  
94.             // Encode to PNG
95.             byte[] bytes = readableTexture.EncodeToPNG();
96.  
97.             // Save the PNG
98.             File.WriteAllBytes($"{dirPath}{obj.name}.png", bytes);
99.  
100.             // Optionally, destroy the copy to free memory
101.             DestroyImmediate(readableTexture);
102.         }
103.     }
104. }
105.  

The images I want to save are like the ones in the first image attached but I only get the images of light blue cube (prefab icon) with the code above.

What am I doing wrong?
AssetPreview.GetMiniThumbnail says "Returns the thumbnail for an object (like the ones you see in the project view)." so it should return the image I see in the project view?

 

I'm sorry that I posted in the wrong place and thank you for moving this post here.

Btw, do you happen to know why this issue (about AssetPreview.GetMiniThumbnail) is happening?

 

I understand! Thank you for your reply

 

Well I figured out how to save the image of prefab shown in Project window in a different way.

I just switched

Texture2D thumbnail = AssetPreview.GetMiniThumbnail(obj);

to

Texture2D thumbnail = AssetPreview.GetAssetPreview(obj);

.

Everything else in the code is the same I posted above and this works fine. (Although images are a bit dark)

But I still don't understand why GetMiniThumbnail doesn't work... If anyone knows please let me know.