diff --git a/back/main.py b/back/main.py
index c33b4ee..5d81a00 100644
--- a/back/main.py
+++ b/back/main.py
@@ -7,7 +7,6 @@ from sqlalchemy.orm import foreign
 import os
 import uuid
 import json
-import imghdr
 from datetime import datetime
 
 app = Flask(__name__)
@@ -211,6 +210,17 @@ def save_hashtags(tag_type, target_id, hashtopic):
             name=tag
         )
         db.session.add(new_tag)
+
+def detect_image_type(header: bytes):
+    if header.startswith(b"\xFF\xD8\xFF"):
+        return "jpeg"
+    if header.startswith(b"\x89PNG\r\n\x1a\n"):
+        return "png"
+    if header.startswith(b"GIF87a") or header.startswith(b"GIF89a"):
+        return "gif"
+    if header.startswith(b"RIFF") and len(header) >= 12 and header[8:12] == b"WEBP":
+        return "webp"
+    return None
     
 # --- 用户普通api端点 ---
 @app.route('/api/settings', methods=['GET'])
@@ -507,7 +517,7 @@ def upload_pic():
 
         header = file.read(512)
         file.seek(0)
-        detected = imghdr.what(None, header)
+        detected = detect_image_type(header)
         ext_map = {
             'jpg': 'jpeg',
             'jpeg': 'jpeg',