backend: move mimetype recognition to backend

backend.py

@@ -1,10 +1,13 @@
 from PIL import Image
 from io import BytesIO
+from mimetypes import types_map as mimetypes
 from zipfile import ZipFile
 import os.path
 import sqlite3
 import werkzeug.exceptions as exceptions
 
+mimetypes['.webp'] = 'image/webp'
+
 
 # https://docs.python.org/3.7/library/sqlite3.html#sqlite3.Connection.row_factory
 def dict_factory(cursor, row):
@@ -192,5 +195,5 @@ class CalibreDB:
 
             return {
                 'data': page_data,
-                'extension': os.path.splitext(page_filename)[1]
+                'mimetype': mimetypes[os.path.splitext(page_filename)[1]]
             }

mangareader.py

@@ -3,7 +3,6 @@ from backend import CalibreDB
 from flask import Flask, jsonify, send_from_directory, send_file, render_template, request
 from flask_cors import CORS
 from werkzeug.routing import BaseConverter
-from mimetypes import types_map as mimetypes
 import os
 
 
@@ -14,8 +13,6 @@ def send_from_cwd(filename):
 app = Flask(__name__, static_folder='frontend/dist/static', template_folder='frontend/dist')
 CORS(app)
 
-mimetypes['.webp'] = 'image/webp'
-
 db = CalibreDB()
 
 # kind of redundant, but avoids returning 200 if page does not exist
@@ -66,8 +63,7 @@ def get_volume_info(volume_id):
 @app.route('/api/volume/<int:volume_id>/page/<int:page_number>')
 def get_volume_page(volume_id, page_number):
     page = db.get_volume_page(volume_id, page_number)
-    mimetype = mimetypes[page['extension']]
-    return send_file(page['data'], mimetype=mimetype)
+    return send_file(page['data'], mimetype=page['mimetype'])
 
 
 if __name__ == '__main__':