Preliminary DjVu support

SideDock fade in animation

lector/parsers/djvu.py

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+# This file is a part of Lector, a Qt based ebook reader
+# Copyright (C) 2017-2019 BasioMeusPuga
+
+# This program is free software: you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+
+# You should have received a copy of the GNU General Public License
+# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+import os
+import collections
+
+import numpy
+import djvu.decode
+from PyQt5 import QtGui
+
+djvu_pixel_format = djvu.decode.PixelFormatRgbMask(0xFF0000, 0xFF00, 0xFF, bpp=32)
+djvu_pixel_format.rows_top_to_bottom = 1
+djvu_pixel_format.y_top_to_bottom = 0
+
+
+class ParseDJVU:
+    def __init__(self, filename, temp_dir, file_md5):
+        self.book = None
+        self.filename = filename
+
+        # Create the temporary directory where
+        # rendered pngs will be stored
+        # This may be skipped in case QImage to QPixmap conversion
+        # stops segfaulting
+        self.extract_dir = os.path.join(temp_dir, file_md5)
+        os.makedirs(self.extract_dir, exist_ok=True)
+
+    def read_book(self):
+        self.book = djvu.decode.Context().new_document(
+            djvu.decode.FileURI(self.filename))
+        self.book.decoding_job.wait()
+
+    def generate_metadata(self):
+        title = os.path.basename(self.filename)
+        author = 'Unknown'
+        year = 9999
+        isbn = None
+        tags = []
+
+        cover_page = self.book.pages[0]
+        cover = render_djvu_page(cover_page, self.extract_dir, True)
+
+        Metadata = collections.namedtuple(
+            'Metadata', ['title', 'author', 'year', 'isbn', 'tags', 'cover'])
+        return Metadata(title, author, year, isbn, tags, cover)
+
+    def generate_content(self):
+        # TODO
+        # See if it's possible to generate a more involved ToC
+
+        content = list(range(len(self.book.pages)))
+        toc = [(1, f'Page {i + 1}', i + 1) for i in content]
+
+        # Return toc, content, images_only
+        return toc, content, True
+
+def render_djvu_page(page, extract_dir, for_cover=False):
+
+    # TODO
+    # Figure out how to calculate image stride
+    bytes_per_line = 13200
+
+    # Yes, but why?
+    mode = 0
+
+    page_job = page.decode(wait=True)
+    width, height = page_job.size
+    rect = (0, 0, width, height)
+    color_buffer = numpy.zeros((height, bytes_per_line), dtype=numpy.uint32)
+    page_job.render(
+        mode, rect, rect, djvu_pixel_format,
+        row_alignment=bytes_per_line,
+        buffer=color_buffer)
+    color_buffer ^= 0xFF000000
+
+    imageFormat = QtGui.QImage.Format_RGB32
+    pageQImage = QtGui.QImage(color_buffer, width, height, imageFormat)
+
+    if for_cover:
+        return pageQImage
+
+    # TODO
+    # Converting from the QImage to the QPixmap directly
+    # outright segfaults sometimes.
+    # This damages caching, speed and my ego
+
+    outfile = os.path.join(extract_dir, 'temporaryPNG.png')
+    pageQImage.save(outfile)
+    pixmap = QtGui.QPixmap()
+    pixmap.load(outfile)
+
+    return pixmap