backend: use webp for thumbnails and cache them

Dockerfile

@@ -27,11 +27,13 @@ COPY --from=requirements /usr/src/app/requirements.txt .
 RUN apk add --no-cache --virtual .deps \
         build-base \
         libjpeg-turbo-dev \
+        libwebp-dev \
         zlib-dev \
     && pip install -r requirements.txt \
     && apk del .deps \
     && apk add --no-cache \
-        libjpeg-turbo
+        libjpeg-turbo \
+        libwebp
 
 COPY --from=frontend /usr/src/app/frontend/dist/ frontend/dist
 

Pipfile

@@ -10,6 +10,7 @@ Flask = "*"
 pillow = "*"
 flask-cors = "*"
 gunicorn = "*"
+flask-caching = "*"
 
 [requires]
 python_version = "3.7"

Pipfile.lock

@@ -1,7 +1,7 @@
 {
     "_meta": {
         "hash": {
-            "sha256": "6bf198e4fcc5777632eb0d839a8259ef2fc737c6df23cbe2923d0d4593ab06e4"
+            "sha256": "92afeeaf4d754a31e04e294f6974bd9616eb0f388ce3d977ae235f3d49fa2eae"
         },
         "pipfile-spec": 6,
         "requires": {
@@ -25,11 +25,19 @@
         },
         "flask": {
             "hashes": [
-                "sha256:a31adc27de06034c657a8dc091cc5fcb0227f2474798409bff0e9674de31a026",
-                "sha256:b5ae63812021cb04174fcff05d560a98387a44d9cccd4652a2bfa131ba4e4c9b"
+                "sha256:13f9f196f330c7c2c5d7a5cf91af894110ca0215ac051b5844701f2bfd934d52",
+                "sha256:45eb5a6fd193d6cf7e0cf5d8a5b31f83d5faae0293695626f539a823e93b13f6"
             ],
             "index": "pypi",
-            "version": "==1.1.0"
+            "version": "==1.1.1"
+        },
+        "flask-caching": {
+            "hashes": [
+                "sha256:52e236cbc836c41a5ced0c0a67b48ad180c9e2b5cb69e881089bba766db5569e",
+                "sha256:b0daabd5249bebfbae3da4c22987bac22047fc8b18ea2716c4fc63d57d218946"
+            ],
+            "index": "pypi",
+            "version": "==1.7.2"
         },
         "flask-cors": {
             "hashes": [
@@ -135,10 +143,10 @@
         },
         "werkzeug": {
             "hashes": [
-                "sha256:865856ebb55c4dcd0630cdd8f3331a1847a819dda7e8c750d3db6f2aa6c0209c",
-                "sha256:a0b915f0815982fb2a09161cb8f31708052d0951c3ba433ccc5e1aa276507ca6"
+                "sha256:87ae4e5b5366da2347eb3116c0e6c681a0e939a33b2805e2c0cbd282664932c4",
+                "sha256:a13b74dd3c45f758d4ebdb224be8f1ab8ef58b3c0ffc1783a8c7d9f4f50227e6"
             ],
-            "version": "==0.15.4"
+            "version": "==0.15.5"
         }
     },
     "develop": {}

backend.py

@@ -8,6 +8,8 @@ import werkzeug.exceptions as exceptions
 
 mimetypes['.webp'] = 'image/webp'
 
+thumbnail_cache = {}
+
 
 # https://docs.python.org/3.7/library/sqlite3.html#sqlite3.Connection.row_factory
 def dict_factory(cursor, row):
@@ -18,12 +20,23 @@ def dict_factory(cursor, row):
 
 
 def generate_thumbnail(filepath):
-    image = Image.open(filepath)
-    image.thumbnail((512, 512))
-    thumbnail = BytesIO()
-    image.save(thumbnail, format='jpeg')
+    if filepath in thumbnail_cache:
+        thumbnail = BytesIO()
+        thumbnail.write(thumbnail_cache[filepath])
+    else:
+        image = Image.open(filepath)
+        image.thumbnail((512, 512))
+        thumbnail = BytesIO()
+        image.save(thumbnail, 'webp')
+        thumbnail.seek(0)
+        thumbnail_cache[filepath] = thumbnail.read()
+
     thumbnail.seek(0)
-    return thumbnail
+
+    return {
+        'data': thumbnail,
+        'mimetype': 'image/webp'
+    }
 
 
 class CalibreDB:

mangareader.py

@@ -51,7 +51,7 @@ def get_series_cover(series_id):
 @app.route('/api/series/<int:series_id>/cover/thumbnail')
 def get_series_cover_thumbnail(series_id):
     thumbnail = db.get_series_cover_thumbnail(series_id)
-    return send_file_with_etag(thumbnail, mimetype='image/jpeg')
+    return send_file_with_etag(thumbnail['data'], mimetype=thumbnail['mimetype'])
 
 
 @app.route('/api/series/<int:series_id>')
@@ -67,7 +67,7 @@ def get_volume_cover(volume_id):
 @app.route('/api/volume/<int:volume_id>/cover/thumbnail')
 def get_volume_cover_thumbnail(volume_id):
     thumbnail = db.get_volume_cover_thumbnail(volume_id)
-    return send_file_with_etag(thumbnail, mimetype='image/jpeg')
+    return send_file_with_etag(thumbnail['data'], mimetype=thumbnail['mimetype'])
 
 
 @app.route('/api/volume/<int:volume_id>')