87 lines
3.0 KiB
Python
87 lines
3.0 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 .input import InputPages
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import numpy
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from PIL import Image
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from dataclasses import dataclass
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from typing import Generator, List
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@dataclass
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class SegmentedPage:
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fg: Image
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bg: Image
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def segment_pages(input_pages: InputPages) -> Generator[SegmentedPage]:
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for page_num, input_page in enumerate(input_pages.pages):
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print('Page {} of {}'.format(page_num + 1, input_pages.num_pages))
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yield segment_page(input_page)
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def segment_page(input_page: Image) -> SegmentedPage:
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# Segment the input page into foreground and background
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# Convert image to foreground/background
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image_rgb = input_page.convert('RGB')
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numpy_rgb = numpy.asarray(image_rgb)
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# Precompute black and white pixels
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black_pixels = (numpy_rgb[:,:,0] == 0) & (numpy_rgb[:,:,1] == 0) & (numpy_rgb[:,:,2] == 0)
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white_pixels = (numpy_rgb[:,:,0] == 255) & (numpy_rgb[:,:,1] == 255) & (numpy_rgb[:,:,2] == 255)
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black_or_white = black_pixels | white_pixels
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# Precompute pixels with all neighbours either black or white
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bw1 = numpy.roll(black_or_white, (1, 1), (0, 1))
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bw1[0,:] = True
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bw1[:,0] = True
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bw2 = numpy.roll(black_or_white, (1, 0), (0, 1))
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bw2[0,:] = True
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bw3 = numpy.roll(black_or_white, (1, -1), (0, 1))
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bw3[0,:] = True
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bw3[:,-1] = True
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bw4 = numpy.roll(black_or_white, (0, -1), (0, 1))
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bw4[:,-1] = True
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bw5 = numpy.roll(black_or_white, (-1, -1), (0, 1))
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bw5[-1,:] = True
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bw5[:,-1] = True
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bw6 = numpy.roll(black_or_white, (-1, 0), (0, 1))
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bw6[-1,:] = True
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bw7 = numpy.roll(black_or_white, (-1, 1), (0, 1))
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bw7[-1,:] = True
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bw7[:,0] = True
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bw8 = numpy.roll(black_or_white, (0, 1), (0, 1))
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bw8[:,0] = True
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bw_neighbours = bw1 & bw2 & bw3 & bw4 & bw5 & bw6 & bw7 & bw8
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# Foreground is only black pixels with all neighbours either black or white
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fg_pixels = black_pixels & bw_neighbours
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# Foreground - white out all non-foreground pixels
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numpy_fg = numpy_rgb.copy()
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numpy_fg[~fg_pixels,:] = [255, 255, 255]
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image_fg = Image.fromarray(numpy_fg, image_rgb.mode)
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# Background - white out all foreground pixels
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numpy_bg = numpy_rgb.copy()
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numpy_bg[fg_pixels,:] = [255, 255, 255]
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image_bg = Image.fromarray(numpy_bg, image_rgb.mode)
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# TODO: Handle case where empty background or foreground
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return SegmentedPage(fg=image_fg, bg=image_bg)
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