Create Thumbnail from IIIF

iiif_prezi3/helpers/add_thumbnail.py

@@ -1,7 +1,8 @@
 from ..loader import monkeypatch_schema
 from ..skeleton import (AccompanyingCanvas, Annotation, AnnotationCollection,
                         AnnotationPage, Canvas, Collection, Manifest,
-                        PlaceholderCanvas, Range, Reference, ResourceItem)
+                        PlaceholderCanvas, Range, Reference, ResourceItem,
+                        ServiceItem, ServiceItem1)
 
 
 class AddThumbnail:
@@ -21,5 +22,104 @@ def add_thumbnail(self, image_url, **kwargs):
         self.thumbnail.append(new_thumbnail)
         return new_thumbnail
 
+    def __get_best_fit_size(self, image_info, preferred_width):
+        if 'sizes' in image_info:
+            return min(
+                (size for size in image_info['sizes'] if size["width"] >= preferred_width),
+                key=lambda size: size["width"],
+                default=image_info['sizes'][-1]
+            )
+        else:
+            return None
 
-monkeypatch_schema([Canvas, PlaceholderCanvas, AccompanyingCanvas, AnnotationPage, Collection, Manifest, Annotation, Range, ResourceItem, AnnotationCollection, Reference], AddThumbnail)
+    def __get_thumbnail_id(self, url, image_info, best_fit, preferred_width, aspect_ratio):
+        context = image_info.get('@context', '')
+        profile_data = image_info.get('profile', [])
+        if isinstance(profile_data, list):
+            profile = next((item for item in profile_data if isinstance(item, str)), '')
+        else:
+            profile = profile_data
+        base_url = url.replace('/info.json', '')
+        if best_fit:
+            width = best_fit['width']
+            height = best_fit.get('height', '')
+            if context == "http://iiif.io/api/image/2/context.json":
+                return f"{base_url}/full/{width},/0/default.jpg"
+            else:
+                return f"{base_url}/full/{width},{height}/0/default.jpg"
+        level_0_profiles = {"http://iiif.io/api/image/2/level0.json", "level0"}
+        if profile not in level_0_profiles:
+            if context == "http://iiif.io/api/image/2/context.json":
+                return f"{base_url}/full/{preferred_width},/0/default.jpg"
+            else:
+                height = int(preferred_width / aspect_ratio)
+                return f"{base_url}/full/{preferred_width},{height}/0/default.jpg"
+        if context == "http://iiif.io/api/image/2/context.json":
+            return f"{base_url}/full/full/0/default.jpg"
+        else:
+            return f"{base_url}/full/max/0/default.jpg"
+
+    def create_thumbnail_from_iiif(self, url, preferred_width=500, **kwargs):
+        """Adds an image thumbnail to a manifest or canvas based on a IIIF service.
+
+        If there is a sizes property, it returns the thumbnail that is closest to the preferred width but larger. If no
+        sizes property exists and it's not level zero image service, it returns a thumbnail with the exact preferred
+        width. Else, it returns the level `full/full` or `full/max`.
+
+        Args:
+            url (str): An HTTP URL which points at a IIIF Image response.
+            preferred_width (int, optional): the preferred width of the thumbnail.
+            **kwargs (): see ResourceItem.
+
+        Returns:
+            new_thumbnail (ResourceItem): The updated list of thumbnails, including the newly-created one.
+        """
+        image_response = ResourceItem(id=url, type='Image')
+        image_info = image_response.set_hwd_from_iiif(url)
+        context = image_info.get('@context', '')
+        aspect_ratio = image_info.get('width') / image_info.get('height')
+        profile_data = image_info.get('profile', [])
+        profile = (
+            profile_data if isinstance(profile_data, str)
+            else next((item for item in profile_data if isinstance(item, str)), '')
+            if isinstance(profile_data, list) else ''
+        )
+        best_fit_size = self.__get_best_fit_size(image_info, preferred_width)
+        thumbnail_id = self.__get_thumbnail_id(url, image_info, best_fit_size, preferred_width, aspect_ratio)
+
+        new_thumbnail = ResourceItem(id=thumbnail_id, type='Image', format="image/jpeg", **kwargs)
+        if best_fit_size:
+            new_thumbnail.width = best_fit_size['width']
+            new_thumbnail.height = best_fit_size['height']
+        else:
+            new_thumbnail.width = preferred_width
+            new_thumbnail.height = int(preferred_width / aspect_ratio)
+
+        if not hasattr(self, 'thumbnail') or self.thumbnail is None:
+            self.thumbnail = []
+
+        service = (
+            ServiceItem1(
+                id=image_info['@id'],
+                profile=profile,
+                type="ImageService2",
+                format="image/jpeg"
+            )
+            if context == "http://iiif.io/api/image/2/context.json"
+            else ServiceItem(
+                id=image_info['id'],
+                profile=profile,
+                type=image_info.get('type', 'ImageService'),
+                format="image/jpeg"
+            )
+        )
+        new_thumbnail.add_service(service)
+        self.thumbnail.append(new_thumbnail)
+        return self.thumbnail
+
+
+monkeypatch_schema(
+    [Canvas, PlaceholderCanvas, AccompanyingCanvas, AnnotationPage, Collection, Manifest, Annotation,
+     Range, ResourceItem, AnnotationCollection, Reference],
+    AddThumbnail
+)