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Comic Input: When grayscaling comic images use 16bit gray for better fidelity. When using the PNG format for images this results in larger files but with better grayscaling fidelity.

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Fixes #1898 (Optimized edge case for comic conversion)
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Kovid Goyal 2023-05-22 11:15:41 +05:30
parent 1eb3d9aee5
commit 306f813566
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1 changed files with 24 additions and 12 deletions
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36
src/calibre/ebooks/comic/input.py
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@ -6,14 +6,16 @@ __docformat__ = 'restructuredtext en'
Based on ideas from comiclrf created by FangornUK.
'''
import os, traceback, time
import os
import time
import traceback
from calibre import extract, prints, walk
from calibre.constants import filesystem_encoding
from calibre.ptempfile import PersistentTemporaryDirectory
from calibre.utils.icu import numeric_sort_key
from calibre.utils.ipc.server import Server
from calibre.utils.ipc.job import ParallelJob
from calibre.utils.ipc.server import Server
from polyglot.queue import Empty
# If the specified screen has either dimension larger than this value, no image
@ -41,6 +43,7 @@ def extract_comic(path_to_comic_file):
def generate_entries_from_dir(path):
from functools import partial
from calibre import walk
ans = {}
for x in walk(path):
@ -105,18 +108,21 @@ class PageProcessor(list): # {{{
self.dest = dest
self.rotate = False
self.src_img_was_grayscaled = False
self.src_img_format = None
self.render()
def render(self):
from qt.core import QImage
from calibre.utils.img import image_from_data, scale_image, crop_image
from calibre.utils.img import crop_image, image_from_data, scale_image
with open(self.path_to_page, 'rb') as f:
img = image_from_data(f.read())
width, height = img.width(), img.height()
if self.num == 0: # First image so create a thumbnail from it
with open(os.path.join(self.dest, 'thumbnail.png'), 'wb') as f:
f.write(scale_image(img, as_png=True)[-1])
self.src_img_was_grayscaled = img.format() in (QImage.Format.Format_Grayscale8, QImage.Format.Format_Grayscale16) or (
self.src_img_format = img.format()
self.src_img_was_grayscaled = self.src_img_format in (QImage.Format.Format_Grayscale8, QImage.Format.Format_Grayscale16) or (
img.format() == QImage.Format.Format_Indexed8 and img.allGray())
self.pages = [img]
if width > height:
@ -131,10 +137,11 @@ class PageProcessor(list): # {{{
def process_pages(self):
from qt.core import QImage
from calibre.utils.img import (
image_to_data, rotate_image, remove_borders_from_image, normalize_image,
add_borders_to_image, resize_image, gaussian_sharpen_image, grayscale_image,
despeckle_image, quantize_image
add_borders_to_image, despeckle_image, gaussian_sharpen_image,
image_to_data, normalize_image, quantize_image, remove_borders_from_image,
resize_image, rotate_image,
)
for i, img in enumerate(self.pages):
if self.rotate:
@ -205,17 +212,22 @@ class PageProcessor(list): # {{{
if not self.opts.dont_sharpen:
img = gaussian_sharpen_image(img, 0.0, 1.0)
if not self.opts.dont_grayscale:
img = grayscale_image(img)
if self.opts.despeckle:
img = despeckle_image(img)
img_is_grayscale = self.src_img_was_grayscaled
if not self.opts.dont_grayscale:
img = img.convertToFormat(QImage.Format.Format_Grayscale16)
img_is_grayscale = True
if self.opts.output_format.lower() == 'png':
if self.opts.colors:
img = quantize_image(img, max_colors=min(256, self.opts.colors))
elif self.src_img_was_grayscaled:
img = img.convertToFormat(QImage.Format.Format_Grayscale8)
elif img_is_grayscale:
uses_256_colors = self.src_img_format in (QImage.Format.Format_Indexed8, QImage.Format.Format_Grayscale8)
final_fmt = QImage.Format.Format_Indexed8 if uses_256_colors else QImage.Format.Format_Grayscale16
if img.format() != final_fmt:
img = img.convertToFormat(final_fmt)
dest = '%d_%d.%s'%(self.num, i, self.opts.output_format)
dest = os.path.join(self.dest, dest)
with open(dest, 'wb') as f: