Always convert images to RGB mode on Transkribus imports

arkindex_tasks/import_files/transkribus.py

@@ -23,10 +23,6 @@ from arkindex_tasks.utils import default_client, retried_request
 logging.basicConfig(format="[%(levelname)s] %(message)s", level=logging.INFO)
 logger = logging.getLogger(__name__)
 
-# Image formats that should not be converted before uploading
-# see https://pillow.readthedocs.io/en/5.1.x/handbook/image-file-formats.html
-VALID_IMAGE_FORMATS = ["JPEG", "JPEG2000", "PNG"]
-
 
 def hash_file(path) -> str:
     md5 = hashlib.md5()
@@ -70,10 +66,9 @@ class TranskribusElement(object):
             shutil.copyfileobj(source, destination)
 
         with Image.open(img_path) as img:
-            if img.format not in VALID_IMAGE_FORMATS:
-                # Convert to RGB if needed
-                if img.mode != "RGB":
-                    img = img.convert("RGB")
+            # Convert to RGB if needed
+            if img.mode != "RGB":
+                img = img.convert("RGB")
 
             # Apply the rotation/transposition from the EXIF orientation tag if it is used
             img = ImageOps.exif_transpose(img)