56 lines
1.9 KiB
Python
56 lines
1.9 KiB
Python
# pdf-segmented: Generate PDFs using separate compression for foreground and background
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# Copyright (C) 2025 Lee Yingtong Li
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#
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# This program is free software: you can redistribute it and/or modify
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# it under the terms of the GNU Affero General Public License as published by
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# the Free Software Foundation, either version 3 of the License, or
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# (at your option) any later version.
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#
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# This program is distributed in the hope that it will be useful,
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# but WITHOUT ANY WARRANTY; without even the implied warranty of
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# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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# GNU Affero General Public License for more details.
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#
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# You should have received a copy of the GNU Affero General Public License
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# along with this program. If not, see <https://www.gnu.org/licenses/>.
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from . import CompressedLayer
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from ..util import assert_has_c44, assert_has_djvuextract
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from PIL import Image
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from dataclasses import dataclass
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import io
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import os
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import subprocess
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import tempfile
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@dataclass
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class IW44Layer(CompressedLayer):
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filename: str
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def cleanup(self):
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os.unlink(self.filename)
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def iw44_compress_layer(layer: Image, dpi: float, tempdir: str) -> IW44Layer:
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assert_has_c44('IW44 compression requires DjVuLibre')
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assert_has_djvuextract('IW44 compression requires DjVuLibre')
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# Save image to PBM temporarily
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_, ppm_file = tempfile.mkstemp(suffix='.ppm', dir=tempdir)
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layer.save(ppm_file, format='ppm')
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# Convert image to IW44
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_, djvu_file = tempfile.mkstemp(suffix='.djvu', dir=tempdir)
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subprocess.run(['c44', '-dpi', str(round(dpi)), ppm_file, djvu_file], check=True)
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# Extract background IW44 file
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_, iw44_file = tempfile.mkstemp(suffix='.iw44', dir=tempdir)
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subprocess.run(['djvuextract', djvu_file, 'BG44={}'.format(iw44_file)], check=True, capture_output=True)
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# Clean up
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os.unlink(ppm_file)
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os.unlink(djvu_file)
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return IW44Layer(filename=iw44_file)
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