Allow a worker to specify the needed size of the image

Closes #231 (closed)

arkindex_worker/cache.py

@@ -102,14 +102,26 @@ class CachedElement(Model):
         database = db
         table_name = "elements"
 
-    def open_image(self, *args, max_size: Optional[int] = None, **kwargs) -> Image:
+    def open_image(
+        self,
+        *args,
+        max_width: Optional[int] = None,
+        max_height: Optional[int] = None,
+        **kwargs,
+    ) -> Image:
         """
         Open this element's image as a Pillow image.
         This does not crop the image to the element's polygon.
         IIIF servers with maxWidth, maxHeight or maxArea restrictions on image size are not supported.
 
+        Warns:
+        ----
+           If both, ``max_width`` and ``max_height`` are set, the image ratio is not preserved.
+
+
         :param *args: Positional arguments passed to [arkindex_worker.image.open_image][]
-        :param max_size: Subresolution of the image.
+        :param max_width: The maximum width of the image.
+        :param max_height: The maximum height of the image.
         :param **kwargs: Keyword arguments passed to [arkindex_worker.image.open_image][]
         :raises ValueError: When this element does not have an image ID or a polygon.
         :return: A Pillow image.
@@ -129,7 +141,7 @@ class CachedElement(Model):
         else:
             box = "full"
 
-        if max_size is None:
+        if max_width is None and max_height is None:
             resize = "full"
         else:
             # Do not resize for polygons that do not exactly match the images
@@ -141,10 +153,17 @@ class CachedElement(Model):
                 resize = "full"
 
             # Do not resize when the image is below the maximum size
-            elif self.image.width <= max_size and self.image.height <= max_size:
+            elif (max_width is None or self.image.width <= max_width) and (
+                max_height is None or self.image.height <= max_height
+            ):
                 resize = "full"
+            elif max_width is not None and max_height is not None:
+                resize = f"{max_width},{max_height}"
             else:
-                ratio = max_size / max(self.image.width, self.image.height)
+                ratio = max(
+                    (max_width or 0) / self.image.width,
+                    (max_height or 0) / self.image.height,
+                )
                 new_width, new_height = int(self.image.width * ratio), int(
                     self.image.height * ratio
                 )
                 resize = f"{new_width},{new_height}"
 
         url = self.image.url
         if not url.endswith("/"):