Do not try to load remote images from file system

arkindex_worker/image.py

 # -*- coding: utf-8 -*-
+import os
 from collections import namedtuple
 from io import BytesIO
 from math import ceil
@@ -24,10 +25,17 @@ def open_image(path, mode="RGB"):
     """
     Open an image from a path or a URL
     """
-    try:
-        image = Image.open(path)
-    except IOError:
+    if (
+        path.startswith("http://")
+        or path.startswith("https://")
+        or not os.path.exists(path)
+    ):
         image = download_image(path)
+    else:
+        try:
+            image = Image.open(path)
+        except (IOError, ValueError):
+            image = download_image(path)
 
     if image.mode != mode:
         image = image.convert(mode)

tests/test_image.py

@@ -6,7 +6,7 @@ from pathlib import Path
 import pytest
 from PIL import Image, ImageChops, ImageOps
 
-from arkindex_worker.image import download_tiles
+from arkindex_worker.image import download_tiles, open_image
 
 FIXTURES = Path(__file__).absolute().parent / "data"
 TILE = FIXTURES / "test_image.jpg"
@@ -101,3 +101,29 @@ def test_download_tiles_small(responses):
     with pytest.raises(ValueError) as e:
         download_tiles("http://nowhere")
     assert str(e.value) == "Expected size 181×240 for tile 0,0, but got 1×1"
+
+
+@pytest.mark.parametrize(
+    "path, is_local",
+    (
+        ("http://somewhere/test.jpg", False),
+        ("https://somewhere/test.jpg", False),
+        ("path/to/something", True),
+        ("/absolute/path/to/something", True),
+    ),
+)
+def test_open_image(path, is_local, monkeypatch):
+    """Check if the path triggers a local load or a remote one"""
+
+    monkeypatch.setattr("os.path.exists", lambda x: True)
+    monkeypatch.setattr(Image, "open", lambda x: Image.new("RGB", (1, 10)))
+    monkeypatch.setattr(
+        "arkindex_worker.image.download_image", lambda x: Image.new("RGB", (10, 1))
+    )
+
+    image = open_image(path)
+
+    if is_local:
+        assert image.size == (1, 10)
+    else:
+        assert image.size == (10, 1)