From 45b7318f083450d0574f7a123735f7fd20342b25 Mon Sep 17 00:00:00 2001
From: Lonami Exo <totufals@hotmail.com>
Date: Thu, 15 Mar 2018 09:52:45 +0100
Subject: [PATCH] Fix Telegram only recognises 3 image filetypes

---
 telethon/utils.py | 11 +++++++----
 1 file changed, 7 insertions(+), 4 deletions(-)

diff --git a/telethon/utils.py b/telethon/utils.py
index daf8c875..ddc920d3 100644
--- a/telethon/utils.py
+++ b/telethon/utils.py
@@ -4,10 +4,11 @@ to convert between an entity like an User, Chat, etc. into its Input version)
 """
 import math
 import mimetypes
+import os
 import re
 import types
 from collections import UserList
-from mimetypes import add_type, guess_extension
+from mimetypes import guess_extension
 
 from .tl.types import (
     Channel, ChannelForbidden, Chat, ChatEmpty, ChatForbidden, ChatFull,
@@ -315,11 +316,13 @@ def get_input_media(media, is_photo=False):
 
 
 def is_image(file):
-    """Returns True if the file extension looks like an image file"""
+    """
+    Returns True if the file extension looks like an image file to Telegram.
+    """
     if not isinstance(file, str):
         return False
-    mime = mimetypes.guess_type(file)[0] or ''
-    return mime.startswith('image/') and not mime.endswith('/webp')
+    _, ext = os.path.splitext(file)
+    return re.match(r'\.(png|jpe?g|gif)', ext, re.IGNORECASE)
 
 
 def is_audio(file):