cbz2ebook: Pad to screen size

This avoids issues with my Kobo Forma, which displays full-width pages
at an offset, if it is preceded by a page which is less wide.

cbz2ebook.py

@@ -1,33 +1,13 @@
 #!/usr/bin/env cached-nix-shell
 #!nix-shell -i python3 -p python3 python3Packages.pillow python3Packages.tqdm
-from PIL import Image
-from concurrent.futures import ThreadPoolExecutor
-from tqdm import tqdm
-from zipfile import ZipFile
 import argparse
 import sys
 import zlib
+from concurrent.futures import ThreadPoolExecutor
+from zipfile import ZipFile
 
-
-def should_scale(in_width, in_height, out_width, out_height):
-    return not (
-        (in_width == out_width and in_height <= out_height)
-        or (in_height == out_height and in_width <= out_width)
-    )
-
-
-def scaled_size(in_width, in_height, out_width, out_height):
-    in_aspect_ratio = float(in_width) / float(in_height)
-    out_aspect_ratio = float(out_width) / float(out_height)
-
-    if in_aspect_ratio > out_aspect_ratio:
-        height = out_width / in_aspect_ratio
-        width = out_width
-    else:
-        width = out_height * in_aspect_ratio
-        height = out_height
-
-    return int(round(width)), round(int(height))
+from PIL import Image, ImageOps
+from tqdm import tqdm
 
 
 def process_image(im):
@@ -38,12 +18,8 @@ def process_image(im):
     # convert to greyscale
     im = im.convert("L")
 
-    # resize if necessary
-    if should_scale(im.width, im.height, args.width, args.height):
-        im = im.resize(
-            scaled_size(im.width, im.height, args.width, args.height),
-            resample=Image.Resampling.LANCZOS,
-        )
+    # pad to screen size
+    im = ImageOps.pad(im, (args.width, args.height), Image.Resampling.LANCZOS, "#fff")
 
     return im