--- a/sat/tools/image.py	Tue Apr 14 20:26:47 2020 +0200
+++ b/sat/tools/image.py	Tue Apr 14 20:29:37 2020 +0200
@@ -19,6 +19,7 @@
 """Methods to manipulate images"""
 
 import tempfile
+import mimetypes
 from PIL import Image
 from pathlib import Path
 from twisted.internet import threads
@@ -85,3 +86,28 @@
         The image at this path should be deleted after use
     """
     return threads.deferToThread(_resizeBlocking, image_path, new_size, dest)
+
+
+def guess_type(source):
+    """Guess image media type
+
+    @param source(str, Path, file): image to guess type
+    @return (str, None): media type, or None if we can't guess
+    """
+    if isinstance(source, str):
+        source = Path(source)
+
+    if isinstance(source, Path):
+        # we first try to guess from file name
+        media_type = mimetypes.guess_type(source, strict=False)[0]
+        if media_type is not None:
+            return media_type
+
+    # file name is not enough, we try to open it
+    img = Image.open(source)
+    try:
+        return Image.MIME[img.format]
+    except KeyError:
+        return None
+
+