Support bounding box for elements using cache

A unit test was invalid, completely ignoring some parameters

arkindex_worker/cache.py

@@ -72,19 +72,28 @@ class CachedElement(Model):
         """
         if not self.image_id or not self.polygon:
             raise ValueError(f"Element {self.id} has no image")
+
+        # Always fetch the image from the bounding box when size differs from full image
+        bounding_box = polygon_bounding_box(self.polygon)
+        if (
+            bounding_box.width != self.image.width
+            or bounding_box.height != self.image.height
+        ):
+            box = f"{bounding_box.x},{bounding_box.y},{bounding_box.x + bounding_box.width},{bounding_box.y + bounding_box.height}"
+        else:
+            box = "full"
+
         if max_size is None:
             resize = "full"
         else:
-            bounding_box = polygon_bounding_box(self.polygon)
             # Do not resize for polygons that do not exactly match the images
+            # as the resize is made directly by the IIIF server using the box parameter
             if (
                 bounding_box.width != self.image.width
                 or bounding_box.height != self.image.height
             ):
                 resize = "full"
-                logger.warning(
-                    "Only full size elements covered, downloading full size image"
-                )
+
             # Do not resize when the image is below the maximum size
             elif self.image.width <= max_size and self.image.height <= max_size:
                 resize = "full"
@@ -99,7 +108,7 @@ class CachedElement(Model):
         if not url.endswith("/"):
             url += "/"
 
-        return open_image(f"{url}full/{resize}/0/default.jpg", *args, **kwargs)
+        return open_image(f"{url}{box}/{resize}/0/default.jpg", *args, **kwargs)
 
 
 class CachedTranscription(Model):