Implement PNG compression

README.md

@@ -1,6 +1,6 @@
 # pdf-segmented
 
-Generate PDFs (or DJVU) using separate compression for foreground and background
+Generate PDFs using separate compression for foreground and background
 
 ## Usage
 
@@ -14,9 +14,7 @@ All black pixels (#000000) will be considered to be foreground, and all remainin
 
 The foreground will be compressed losslessly using [JBIG2](https://en.wikipedia.org/wiki/JBIG2). The background will be compressed lossily using [JPEG](https://en.wikipedia.org/wiki/JPEG). JPEG quality can be controlled using the `--jpeg-quality` option; the default is the Pillow default (75% at time of writing).
 
-Additional compression algorithms are supported (JPEG 2000, PNG); see `--help` for detailed options. DJVU output (foreground JB2, background IW44) is also supported.
+Dependencies:
-
-## Dependencies
 
 * [Python 3](https://www.python.org/) (tested using 3.13.3)
 	* [NumPy](https://numpy.org/) (tested using 2.2.5)

pdf_segmented/__init__.py

@@ -16,7 +16,6 @@
 
 from .compression import CompressionOptions, compress_pages
 from .input.xcf import xcf_get_pages
-from .output.djvu import djvu_write_pages
 from .output.pdf import pdf_write_pages
 from .segmentation import segment_pages
 
@@ -30,8 +29,8 @@ def convert_file(
 	output_file: str,
 	input_format: Optional[str] = None,
 	output_format: Optional[str] = None,
-	fg_compression: Optional[str] = None,
+	fg_compression: str = 'jbig2',
-	bg_compression: Optional[str] = None,
+	bg_compression: str = 'jpeg',
 	options: CompressionOptions = CompressionOptions()
 ) -> None:
 	# Create temporary directory
@@ -44,48 +43,11 @@ def convert_file(
 				input_format = 'xcf'
 			else:
 				print('Warning: Unknown input file extension, assuming XCF', file=sys.stderr)
-		
 		if output_format is None:
 			if output_file.endswith('.pdf'):
 				output_format = 'pdf'
-			elif output_file.endswith('.djvu'):
-				output_format = 'djvu'
 			else:
-				print('Error: Unknown output file extension (try --output-format)', file=sys.stderr)
+				print('Warning: Unknown output file extension, assuming PDF', file=sys.stderr)
-				sys.exit(1)
-		
-		if fg_compression is None:
-			if output_format == 'pdf':
-				fg_compression = 'jbig2'
-			elif output_format == 'djvu':
-				fg_compression = 'jb2'
-			else:
-				raise NotImplementedError()
-		
-		if bg_compression is None:
-			if output_format == 'pdf':
-				bg_compression = 'jpeg'
-			elif output_format == 'djvu':
-				bg_compression = 'iw44'
-			else:
-				raise NotImplementedError()
-		
-		# Validate format compatibility
-		if output_format == 'pdf':
-			if bg_compression not in ('jp2', 'jpeg', 'png'):
-				print('Error: Unsupported --bg-compression for PDF format (supported: jp2, jpeg, png)')
-				sys.exit(1)
-			if fg_compression not in ('jbig2', 'png'):
-				print('Error: Unsupported --fg-compression for PDF format (supported: jp2, jpeg, png)')
-				sys.exit(1)
-		
-		if output_format == 'djvu':
-			if bg_compression != 'iw44':
-				print('Error: Unsupported --bg-compression for DJVU format (supported: iw44)')
-				sys.exit(1)
-			if fg_compression != 'jb2':
-				print('Error: Unsupported --fg-compression for DJVU format (supported: jb2)')
-				sys.exit(1)
 		
 		# Get input pages
 		if input_format == 'xcf':
@@ -98,7 +60,6 @@ def convert_file(
 		
 		# Compress layers
 		compressed_pages = compress_pages(
-			input_pages=input_pages,
 			segmented_pages=segmented_pages,
 			fg_compression=fg_compression,
 			bg_compression=bg_compression,
@@ -113,13 +74,6 @@ def convert_file(
 				compressed_pages=compressed_pages,
 				output_file=output_file
 			)
-		elif output_format == 'djvu':
-			djvu_write_pages(
-				input_pages=input_pages,
-				compressed_pages=compressed_pages,
-				output_file=output_file,
-				tempdir=tempdir
-			)
 		else:
 			raise NotImplementedError()
 	finally:

pdf_segmented/__main__.py

@@ -27,9 +27,9 @@ parser = argparse.ArgumentParser(
 parser.add_argument('input_file')
 parser.add_argument('output_file')
 parser.add_argument('--input-format', choices=['xcf'])
-parser.add_argument('--output-format', choices=['pdf', 'djvu'])
+parser.add_argument('--output-format', choices=['pdf'])
-parser.add_argument('--fg-compression', choices=['jbig2', 'png', 'jb2'])
+parser.add_argument('--fg-compression', default='jbig2', choices=['jbig2', 'png'])
-parser.add_argument('--bg-compression', choices=['jpeg', 'jp2', 'png', 'iw44'])
+parser.add_argument('--bg-compression', default='jpeg', choices=['jpeg', 'jp2', 'png'])
 parser.add_argument('--jp2-lossless', action='store_true')
 parser.add_argument('--jp2-rate', type=float)
 parser.add_argument('--jpeg-quality', type=float)

pdf_segmented/compression/__init__.py

@@ -17,17 +17,14 @@
 class CompressedLayer:
 	# Superclass for all compressed layer types (JPEG, JBIG2, etc.)
 	
-	def cleanup(self):
+	def cleanup():
 		# Clean up any temporary files, etc.
 		pass
 
-from .iw44 import iw44_compress_layer
-from .jb2 import jb2_compress_layer
 from .jbig2 import jbig2_compress_layer
 from .jp2 import jp2_compress_layer
 from .jpeg import jpeg_compress_layer
 from .png import png_compress_layer
-from ..input import InputPages
 from ..segmentation import SegmentedPage
 
 from PIL import Image
@@ -47,7 +44,6 @@ class CompressedPage:
 	bg: CompressedLayer
 
 def compress_pages(
-	input_pages: InputPages,
 	segmented_pages: Iterable[SegmentedPage],
 	fg_compression: str,
 	bg_compression: str,
@@ -58,7 +54,6 @@ def compress_pages(
 	# Compress foreground and background layers on each segmented page
 	for segmented_page in segmented_pages:
 		yield compress_page(
-			input_pages=input_pages,
 			segmented_page=segmented_page,
 			fg_compression=fg_compression,
 			bg_compression=bg_compression,
@@ -67,7 +62,6 @@ def compress_pages(
 		)
 
 def compress_page(
-	input_pages: InputPages,
 	segmented_page: SegmentedPage,
 	fg_compression: str,
 	bg_compression: str,
@@ -78,7 +72,6 @@ def compress_page(
 	# Compress foreground and background layers
 	return CompressedPage(
 		fg=compress_layer(
-			input_pages=input_pages,
 			layer=segmented_page.fg,
 			compression=fg_compression,
 			is_foreground=True,
@@ -86,7 +79,6 @@ def compress_page(
 			tempdir=tempdir
 		),
 		bg=compress_layer(
-			input_pages=input_pages,
 			layer=segmented_page.bg,
 			compression=bg_compression,
 			is_foreground=False,
@@ -96,7 +88,6 @@ def compress_page(
 	)
 
 def compress_layer(
-	input_pages: InputPages,
 	layer: Image,
 	compression: str,
 	is_foreground: bool,
@@ -105,11 +96,7 @@ def compress_layer(
 ) -> CompressedLayer:
 	
 	# Compress the given layer
-	if compression == 'iw44':
+	if compression == 'jbig2':
-		return iw44_compress_layer(layer=layer, dpi=input_pages.dpi, tempdir=tempdir)
-	elif compression == 'jb2':
-		return jb2_compress_layer(layer=layer, dpi=input_pages.dpi, tempdir=tempdir)
-	elif compression == 'jbig2':
 		return jbig2_compress_layer(layer=layer, tempdir=tempdir)
 	elif compression == 'jp2':
 		return jp2_compress_layer(layer=layer, jp2_lossless=options.jp2_lossless, jp2_rate=options.jp2_rate)

pdf_segmented/compression/iw44.py

@@ -1,55 +0,0 @@
-#   pdf-segmented: Generate PDFs using separate compression for foreground and background
-#   Copyright (C) 2025  Lee Yingtong Li
-#
-#   This program is free software: you can redistribute it and/or modify
-#   it under the terms of the GNU Affero 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 Affero General Public License for more details.
-#
-#   You should have received a copy of the GNU Affero General Public License
-#   along with this program.  If not, see <https://www.gnu.org/licenses/>.
-
-from . import CompressedLayer
-from ..util import assert_has_c44, assert_has_djvuextract
-
-from PIL import Image
-
-from dataclasses import dataclass
-import io
-import os
-import subprocess
-import tempfile
-
-@dataclass
-class IW44Layer(CompressedLayer):
-	filename: str
-	
-	def cleanup(self):
-		os.unlink(self.filename)
-
-def iw44_compress_layer(layer: Image, dpi: float, tempdir: str) -> IW44Layer:
-	assert_has_c44('IW44 compression requires DjvuLibre')
-	assert_has_djvuextract('IW44 compression requires DjvuLibre')
-	
-	# Save image to PBM temporarily
-	_, ppm_file = tempfile.mkstemp(suffix='.ppm', dir=tempdir)
-	layer.save(ppm_file, format='ppm')
-	
-	# Convert image to IW44
-	_, djvu_file = tempfile.mkstemp(suffix='.djvu', dir=tempdir)
-	subprocess.run(['c44', '-dpi', str(round(dpi)), ppm_file, djvu_file], check=True)
-	
-	# Extract background IW44 file
-	_, iw44_file = tempfile.mkstemp(suffix='.iw44', dir=tempdir)
-	subprocess.run(['djvuextract', djvu_file, 'BG44={}'.format(iw44_file)], check=True, capture_output=True)
-	
-	# Clean up
-	os.unlink(ppm_file)
-	os.unlink(djvu_file)
-	
-	return IW44Layer(filename=iw44_file)

pdf_segmented/compression/jb2.py

@@ -1,49 +0,0 @@
-#   pdf-segmented: Generate PDFs using separate compression for foreground and background
-#   Copyright (C) 2025  Lee Yingtong Li
-#
-#   This program is free software: you can redistribute it and/or modify
-#   it under the terms of the GNU Affero 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 Affero General Public License for more details.
-#
-#   You should have received a copy of the GNU Affero General Public License
-#   along with this program.  If not, see <https://www.gnu.org/licenses/>.
-
-from . import CompressedLayer
-from ..util import assert_has_cjb2
-
-from PIL import Image
-
-from dataclasses import dataclass
-import io
-import os
-import subprocess
-import tempfile
-
-@dataclass
-class JB2Layer(CompressedLayer):
-	filename: str
-	
-	def cleanup(self):
-		os.unlink(self.filename)
-
-def jb2_compress_layer(layer: Image, dpi: float, tempdir: str) -> JB2Layer:
-	assert_has_cjb2('JB2 compression requires DjvuLibre')
-	
-	# Save image to PPM temporarily
-	_, pbm_file = tempfile.mkstemp(suffix='.pbm', dir=tempdir)
-	layer.convert('1').save(pbm_file, format='ppm')
-	
-	# Convert image to JB2
-	_, jb2_file = tempfile.mkstemp(suffix='.djvu', dir=tempdir)
-	subprocess.run(['cjb2', '-dpi', str(round(dpi)), pbm_file, jb2_file], check=True)
-	
-	# Clean up
-	os.unlink(pbm_file)
-	
-	return JB2Layer(filename=jb2_file)

pdf_segmented/compression/jp2.py

@@ -1,39 +0,0 @@
-#   pdf-segmented: Generate PDFs using separate compression for foreground and background
-#   Copyright (C) 2025  Lee Yingtong Li
-#
-#   This program is free software: you can redistribute it and/or modify
-#   it under the terms of the GNU Affero 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 Affero General Public License for more details.
-#
-#   You should have received a copy of the GNU Affero General Public License
-#   along with this program.  If not, see <https://www.gnu.org/licenses/>.
-
-from . import CompressedLayer
-
-from PIL import Image
-
-from dataclasses import dataclass
-import io
-from typing import Optional
-
-@dataclass
-class JP2Layer(CompressedLayer):
-	data: bytes
-
-def jp2_compress_layer(layer: Image, jp2_lossless: bool, jp2_rate: Optional[float]) -> JP2Layer:
-	save_kwargs = {}
-	if jp2_rate is not None:
-		save_kwargs['quality_mode'] = 'rates'
-		save_kwargs['quality_layers'] = [jp2_rate]
-	
-	# Save image to JPEG 2000
-	bytesio = io.BytesIO()
-	layer.save(bytesio, format='jpeg2000', no_jp2=False, irreversible=not jp2_lossless, **save_kwargs)
-	
-	return JP2Layer(data=bytesio.getvalue())

pdf_segmented/compression/png.py

@@ -1,61 +0,0 @@
-#   pdf-segmented: Generate PDFs using separate compression for foreground and background
-#   Copyright (C) 2025  Lee Yingtong Li
-#
-#   This program is free software: you can redistribute it and/or modify
-#   it under the terms of the GNU Affero 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 Affero General Public License for more details.
-#
-#   You should have received a copy of the GNU Affero General Public License
-#   along with this program.  If not, see <https://www.gnu.org/licenses/>.
-
-from . import CompressedLayer
-
-from PIL import Image
-
-from dataclasses import dataclass
-import io
-import struct
-
-@dataclass
-class PNGLayer(CompressedLayer):
-	data: bytes
-	
-	def get_flate_data(self):
-		# Parse PNG data to get the IDAT chunks
-		bytesio = io.BytesIO(self.data)
-		bytesio.read(8)  # Read PNG header
-		
-		flate_data = bytearray()
-		
-		while True:
-			# Read PNG chunks
-			length_bytes = bytesio.read(4)
-			if length_bytes == b'':  # EOF
-				break
-			length = struct.unpack('>I', length_bytes)[0]
-			cid = bytesio.read(4)
-			data = bytesio.read(length)
-			crc = bytesio.read(4)
-			
-			# IDAT chunk contains DEFLATE data
-			if cid == b'IDAT':
-				flate_data.extend(data)
-		
-		return bytes(flate_data)
-
-def png_compress_layer(layer: Image, is_foreground: bool) -> PNGLayer:
-	if is_foreground:
-		# Foreground is 1bpp
-		layer = layer.convert('1')
-	
-	# Save image to PNG
-	bytesio = io.BytesIO()
-	layer.save(bytesio, format='png', optimize=True)
-	
-	return PNGLayer(data=bytesio.getvalue())

pdf_segmented/output/djvu.py

@@ -1,62 +0,0 @@
-#   pdf-segmented: Generate PDFs using separate compression for foreground and background
-#   Copyright (C) 2025  Lee Yingtong Li
-#
-#   This program is free software: you can redistribute it and/or modify
-#   it under the terms of the GNU Affero 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 Affero General Public License for more details.
-#
-#   You should have received a copy of the GNU Affero General Public License
-#   along with this program.  If not, see <https://www.gnu.org/licenses/>.
-
-from ..compression import CompressedPage
-from ..input import InputPages
-from ..util import assert_has_djvm, assert_has_djvumake
-
-import os
-import subprocess
-import tempfile
-from typing import Generator
-
-def djvu_write_pages(
-	input_pages: InputPages,
-	compressed_pages: Generator[CompressedPage],
-	output_file: str,
-	tempdir: str
-) -> None:
-	
-	assert_has_djvm('DJVU output requires DjvuLibre')
-	assert_has_djvumake('DJVU output requires DjvuLibre')
-	
-	djvu_page_files = []
-	
-	try:
-		# Write each page
-		for compressed_page in compressed_pages:
-			try:
-				# Combine foreground and background
-				_, page_djvu_file = tempfile.mkstemp(suffix='.djvu', dir=tempdir)
-				
-				# TODO: Handle case where empty background or foreground
-				args = ['djvumake', page_djvu_file, 'INFO={},{},{}'.format(input_pages.width, input_pages.height, round(input_pages.dpi))]
-				args.append('Sjbz={}'.format(compressed_page.fg.filename))
-				args.append('BG44={}'.format(compressed_page.bg.filename))
-				subprocess.run(args, check=True, capture_output=True)
-				
-				djvu_page_files.append(page_djvu_file)
-			finally:
-				# Clean up
-				compressed_page.bg.cleanup()
-				compressed_page.fg.cleanup()
-		
-		# Combine pages
-		subprocess.run(['djvm', '-c', output_file] + djvu_page_files, check=True)
-	finally:
-		# Clean up
-		for page_djvu_file in djvu_page_files:
-			os.unlink(page_djvu_file)

pdf_segmented/output/pdf.py

@@ -42,15 +42,10 @@ def pdf_write_pages(
 		page = pdf.add_blank_page(page_size=(width_pt, height_pt))
 		
 		# Write each layer to the page
-		# TODO: Handle case where empty background or foreground
 		content_instructions = []
 		pdf_write_layer(input_pages=input_pages, pdf=pdf, page=page, layer=compressed_page.bg, is_foreground=False, content_instructions=content_instructions)
 		pdf_write_layer(input_pages=input_pages, pdf=pdf, page=page, layer=compressed_page.fg, is_foreground=True, content_instructions=content_instructions)
 		
-		# Clean up
-		compressed_page.bg.cleanup()
-		compressed_page.fg.cleanup()
-		
 		# Generate content stream
 		wrapped_instructions = [
 			ContentStreamInstruction([], Operator('q')),

pdf_segmented/util.py

@@ -17,31 +17,6 @@
 import shutil
 import sys
 
-def assert_has_c44(error_message: str = 'DjvuLibre is required') -> None:
-	if shutil.which('c44') is None:
-		print('Error: {} (c44 not found on PATH)'.format(error_message), file=sys.stderr)
-		sys.exit(1)
-
-def assert_has_cjb2(error_message: str = 'DjvuLibre is required') -> None:
-	if shutil.which('cjb2') is None:
-		print('Error: {} (cjb2 not found on PATH)'.format(error_message), file=sys.stderr)
-		sys.exit(1)
-
-def assert_has_djvm(error_message: str = 'DjvuLibre is required') -> None:
-	if shutil.which('djvm') is None:
-		print('Error: {} (djvm not found on PATH)'.format(error_message), file=sys.stderr)
-		sys.exit(1)
-
-def assert_has_djvuextract(error_message: str = 'DjvuLibre is required') -> None:
-	if shutil.which('djvuextract') is None:
-		print('Error: {} (djvuextract not found on PATH)'.format(error_message), file=sys.stderr)
-		sys.exit(1)
-
-def assert_has_djvumake(error_message: str = 'DjvuLibre is required') -> None:
-	if shutil.which('djvumake') is None:
-		print('Error: {} (djvumake not found on PATH)'.format(error_message), file=sys.stderr)
-		sys.exit(1)
-
 def assert_has_imagemagick(error_message: str = 'ImageMagick is required') -> None:
 	if shutil.which('magick') is None:
 		print('Error: {} (magick not found on PATH)'.format(error_message), file=sys.stderr)