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Rejig thumbnail dimension calculations

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Instead of bounding the the requested values, we *expand* around those,
like downloaded thumbnails for store-bought KePubs.

Also handle wonky landscape source ARs properly while we're there.
This commit is contained in:
NiLuJe 2019-05-23 23:51:25 +02:00
parent 1f0bc97a15
commit cf1b855ea0
1 changed files with 24 additions and 12 deletions
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36
src/calibre/devices/kobo/driver.py
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@ -2644,20 +2644,27 @@ class KOBOTOUCH(KOBO):
path = os.path.join(path, imageId)
return path
def _calculate_kobo_cover_size(self, library_size, kobo_size, keep_cover_aspect, letterbox):
def _calculate_kobo_cover_size(self, library_size, kobo_size, expand, keep_cover_aspect, letterbox):
# Remember the canvas size
canvas_size = kobo_size
# NOTE: Loosely based on Qt's QSize::scaled implementation
if keep_cover_aspect:
# NOTE: Py3k wouldn't need explicit casts to return a float
# NOTE: Ideally, the target AR should be 0.75, but that's rarely exactly the case for thumbnails,
# which is why we try to limit accumulating even more rounding errors on top of Nickel's.
library_aspect = library_size[0] / float(library_size[1])
kobo_aspect = kobo_size[0] / float(kobo_size[1])
if library_aspect > kobo_aspect:
kobo_size = (kobo_size[0], int(round(kobo_size[0] / library_aspect)))
# NOTE: Unlike Qt, we round to avoid accumulating errors
aspect_ratio = library_size[0] / float(library_size[1])
rescaled_width = int(round(kobo_size[1] * aspect_ratio))
if expand:
use_height = (rescaled_width >= kobo_size[0])
else:
kobo_size = (int(round(library_aspect * kobo_size[1])), kobo_size[1])
use_height = (rescaled_width <= kobo_size[0])
if use_height:
kobo_size = (rescaled_width, kobo_size[1])
else:
kobo_size = (kobo_size[0], int(round(kobo_size[0] / aspect_ratio)))
# Did we actually want to letterbox?
if not letterbox:
canvas_size = kobo_size
@ -2757,13 +2764,18 @@ class KOBOTOUCH(KOBO):
# Never letterbox thumbnails, that's ugly. But for fullscreen covers, honor the setting.
letterbox = letterbox_fs_covers if is_full_size else False
resize_to, minify_to = self._calculate_kobo_cover_size(library_cover_size, kobo_size, keep_cover_aspect, letterbox)
# NOTE: Full size means we have to fit *inside* the given boundaries. Thumbnails, on the other hand, are *expanded* around those boundaries.
# In Qt, it'd mean full-screen covers are resized using Qt::KeepAspectRatio, while thumbnails are resized using Qt::KeepAspectRatioByExpanding
# (i.e., QSize's boundedTo() vs. expandedTo(). See also IM's '^' geometry token, for the same "expand" behavior.)
# Note that Nickel itself will generate bounded thumbnails, while it will download expanded thumbnails for store-bought KePubs...
# We chose to emulate the KePub behavior.
resize_to, expand_to = self._calculate_kobo_cover_size(library_cover_size, kobo_size, expand=not is_full_size, keep_cover_aspect, letterbox)
if show_debug:
debug_print("KoboTouch:_calculate_kobo_cover_size - minify_to=%s (vs. kobo_size=%s) & resize_to=%s, keep_cover_aspect=%s & letterbox_fs_covers=%s, png_covers=%s" % (
minify_to, kobo_size, resize_to, keep_cover_aspect, letterbox_fs_covers, png_covers))
debug_print("KoboTouch:_calculate_kobo_cover_size - expand_to=%s (vs. kobo_size=%s) & resize_to=%s, keep_cover_aspect=%s & letterbox_fs_covers=%s, png_covers=%s" % (
expand_to, kobo_size, resize_to, keep_cover_aspect, letterbox_fs_covers, png_covers))
# Return the data resized and properly grayscaled/dithered/letterboxed if requested
data = self._create_cover_data(cover_data, resize_to, minify_to, kobo_size, upload_grayscale, dithered_covers, keep_cover_aspect, is_full_size, letterbox, png_covers)
data = self._create_cover_data(cover_data, resize_to, expand_to, kobo_size, upload_grayscale, dithered_covers, keep_cover_aspect, is_full_size, letterbox, png_covers)
with lopen(fpath, 'wb') as f:
f.write(data)