Download fonts at app startup instead

We can't bake the font into the Docker image as such, because we mount
the volumes which blows away anything we have in the app tree
beforehand.

We could stash it somewhere in the image and then copy it from there on
app startup or something, but at that point we might as well just
download it as part of the app startup.

bookwyrm/preview_images.py

@@ -4,6 +4,8 @@ import os
 import textwrap
 from io import BytesIO
 from uuid import uuid4
+import urllib
+import logging
 
 import colorsys
 from colorthief import ColorThief
@@ -17,29 +19,37 @@ from django.db.models import Avg
 from bookwyrm import models, settings
 from bookwyrm.tasks import app
 
+logger = logging.getLogger(__name__)
 
 IMG_WIDTH = settings.PREVIEW_IMG_WIDTH
 IMG_HEIGHT = settings.PREVIEW_IMG_HEIGHT
 BG_COLOR = settings.PREVIEW_BG_COLOR
 TEXT_COLOR = settings.PREVIEW_TEXT_COLOR
 DEFAULT_COVER_COLOR = settings.PREVIEW_DEFAULT_COVER_COLOR
+DEFAULT_FONT = settings.PREVIEW_DEFAULT_FONT
 TRANSPARENT_COLOR = (0, 0, 0, 0)
 
 margin = math.floor(IMG_HEIGHT / 10)
 gutter = math.floor(margin / 2)
 inner_img_height = math.floor(IMG_HEIGHT * 0.8)
 inner_img_width = math.floor(inner_img_height * 0.7)
-font_dir = os.path.join(settings.STATIC_ROOT, "fonts/source_han_sans")
+
+
+def get_imagefont(name, size):
+    try:
+        config = settings.FONTS[name]
+        path = os.path.join(settings.FONT_DIR, config["directory"], config["filename"])
+        return ImageFont.truetype(path, size)
+    except KeyError:
+        logger.error("Font %s not found in config", name)
+    except OSError:
+        logger.error("Could not load font %s from file", name)
+
+    return ImageFont.load_default()
 
 
 def get_font(weight, size=28):
-    """Loads custom font"""
-    font_path = os.path.join(font_dir, "SourceHanSans-VF.ttf.ttc")
-
-    try:
-        font = ImageFont.truetype(font_path, size)
-    except OSError:
-        font = ImageFont.load_default()
+    font = get_imagefont(DEFAULT_FONT, size)
 
     try:
         if weight == "light":