itextpdf.jar is a component in iText 5 Java library to provide core functionalities. iText Java library allows you to generate and manage PDF documents.

The Source Code files are provided at iText GitHub site.

You can compile it to generate your JAR file, using pom.xml as the build configuration file.

The source code of itextpdf-5.5.14.jar is provided below:

⏎ com/itextpdf/text/pdf/codec/JBIG2SegmentReader.java

/*
 *
 * This file is part of the iText (R) project.
    Copyright (c) 1998-2020 iText Group NV
 * Authors: Bruno Lowagie, Paulo Soares, et al.
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU Affero General Public License version 3
 * as published by the Free Software Foundation with the addition of the
 * following permission added to Section 15 as permitted in Section 7(a):
 * FOR ANY PART OF THE COVERED WORK IN WHICH THE COPYRIGHT IS OWNED BY
 * ITEXT GROUP. ITEXT GROUP DISCLAIMS THE WARRANTY OF NON INFRINGEMENT
 * OF THIRD PARTY RIGHTS
 *
 * 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 http://www.gnu.org/licenses or write to
 * the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
 * Boston, MA, 02110-1301 USA, or download the license from the following URL:
 * http://itextpdf.com/terms-of-use/
 *
 * The interactive user interfaces in modified source and object code versions
 * of this program must display Appropriate Legal Notices, as required under
 * Section 5 of the GNU Affero General Public License.
 *
 * In accordance with Section 7(b) of the GNU Affero General Public License,
 * a covered work must retain the producer line in every PDF that is created
 * or manipulated using iText.
 *
 * You can be released from the requirements of the license by purchasing
 * a commercial license. Buying such a license is mandatory as soon as you
 * develop commercial activities involving the iText software without
 * disclosing the source code of your own applications.
 * These activities include: offering paid services to customers as an ASP,
 * serving PDFs on the fly in a web application, shipping iText with a closed
 * source product.
 *
 * For more information, please contact iText Software Corp. at this
 * address: sales@itextpdf.com
 */
package com.itextpdf.text.pdf.codec;

import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.util.Iterator;
import java.util.SortedMap;
import java.util.SortedSet;
import java.util.TreeMap;
import java.util.TreeSet;

import com.itextpdf.text.error_messages.MessageLocalization;
import com.itextpdf.text.pdf.RandomAccessFileOrArray;

/**
 * Class to read a JBIG2 file at a basic level: understand all the segments,
 * understand what segments belong to which pages, how many pages there are,
 * what the width and height of each page is, and global segments if there
 * are any.  Or: the minimum required to be able to take a normal sequential
 * or random-access organized file, and be able to embed JBIG2 pages as images
 * in a PDF.
 *
 * TODO: the indeterminate-segment-size value of dataLength, else?
 *
 * @since 2.1.5
 */

public class JBIG2SegmentReader {

	public static final int SYMBOL_DICTIONARY = 0; //see 7.4.2.

	public static final int INTERMEDIATE_TEXT_REGION = 4; //see 7.4.3.
	public static final int IMMEDIATE_TEXT_REGION = 6; //see 7.4.3.
	public static final int IMMEDIATE_LOSSLESS_TEXT_REGION = 7; //see 7.4.3.
	public static final int PATTERN_DICTIONARY = 16; //see 7.4.4.
	public static final int INTERMEDIATE_HALFTONE_REGION = 20; //see 7.4.5.
	public static final int IMMEDIATE_HALFTONE_REGION = 22; //see 7.4.5.
	public static final int IMMEDIATE_LOSSLESS_HALFTONE_REGION = 23; //see 7.4.5.
	public static final int INTERMEDIATE_GENERIC_REGION = 36; //see 7.4.6.
	public static final int IMMEDIATE_GENERIC_REGION = 38; //see 7.4.6.
	public static final int IMMEDIATE_LOSSLESS_GENERIC_REGION = 39; //see 7.4.6.
	public static final int INTERMEDIATE_GENERIC_REFINEMENT_REGION = 40; //see 7.4.7.
	public static final int IMMEDIATE_GENERIC_REFINEMENT_REGION = 42; //see 7.4.7.
	public static final int IMMEDIATE_LOSSLESS_GENERIC_REFINEMENT_REGION = 43; //see 7.4.7.

	public static final int PAGE_INFORMATION = 48; //see 7.4.8.
	public static final int END_OF_PAGE = 49; //see 7.4.9.
	public static final int END_OF_STRIPE = 50; //see 7.4.10.
	public static final int END_OF_FILE = 51; //see 7.4.11.
	public static final int PROFILES = 52; //see 7.4.12.
	public static final int TABLES = 53; //see 7.4.13.
	public static final int EXTENSION = 62; //see 7.4.14.

	private final SortedMap<Integer, JBIG2Segment> segments = new TreeMap<Integer, JBIG2Segment>();
	private final SortedMap<Integer, JBIG2Page> pages = new TreeMap<Integer, JBIG2Page>();
	private final SortedSet<JBIG2Segment> globals = new TreeSet<JBIG2Segment>();
	private RandomAccessFileOrArray ra;
	private boolean sequential;
	private boolean number_of_pages_known;
	private int number_of_pages = -1;
	private boolean read = false;

	/**
	 * Inner class that holds information about a JBIG2 segment.
	 * @since	2.1.5
	 */
	public static class JBIG2Segment implements Comparable<JBIG2Segment> {

		public final int segmentNumber;
		public long dataLength = -1;
		public int page = -1;
		public int[] referredToSegmentNumbers = null;
		public boolean[] segmentRetentionFlags = null;
		public int type = -1;
		public boolean deferredNonRetain = false;
		public int countOfReferredToSegments = -1;
		public byte[] data = null;
		public byte[] headerData = null;
		public boolean page_association_size = false;
		public int page_association_offset = -1;

		public JBIG2Segment(int segment_number) {
			this.segmentNumber = segment_number;
		}

		public int compareTo(JBIG2Segment s) {
			return this.segmentNumber - s.segmentNumber;
		}


	}
	/**
	 * Inner class that holds information about a JBIG2 page.
	 * @since	2.1.5
	 */
	public static class JBIG2Page {
		public final int page;
		private final JBIG2SegmentReader sr;
		private final SortedMap<Integer, JBIG2Segment> segs = new TreeMap<Integer, JBIG2Segment>();
		public int pageBitmapWidth = -1;
		public int pageBitmapHeight = -1;
		public JBIG2Page(int page, JBIG2SegmentReader sr) {
			this.page = page;
			this.sr = sr;
		}
		/**
		 * return as a single byte array the header-data for each segment in segment number
		 * order, EMBEDDED organization, but i am putting the needed segments in SEQUENTIAL organization.
		 * if for_embedding, skip the segment types that are known to be not for acrobat.
		 * @param for_embedding
		 * @return	a byte array
		 * @throws IOException
		 */
		public byte[] getData(boolean for_embedding) throws IOException {
			ByteArrayOutputStream os = new ByteArrayOutputStream();
			for (Integer sn : segs.keySet()) {
				JBIG2Segment s = segs.get(sn);

				// pdf reference 1.4, section 3.3.6 JBIG2Decode Filter
				// D.3 Embedded organisation
				if ( for_embedding &&
						( s.type == END_OF_FILE || s.type == END_OF_PAGE ) ) {
					continue;
				}

				if ( for_embedding ) {
					// change the page association to page 1
					byte[] headerData_emb = copyByteArray(s.headerData);
					if ( s.page_association_size ) {
						headerData_emb[s.page_association_offset] = 0x0;
						headerData_emb[s.page_association_offset+1] = 0x0;
						headerData_emb[s.page_association_offset+2] = 0x0;
						headerData_emb[s.page_association_offset+3] = 0x1;
					} else {
						headerData_emb[s.page_association_offset] = 0x1;
					}
					os.write(headerData_emb);
				} else {
					os.write(s.headerData);
				}
				os.write(s.data);
			}
			os.close();
			return os.toByteArray();
		}
		public void addSegment(JBIG2Segment s) {
			segs.put(Integer.valueOf(s.segmentNumber), s);
		}

	}

	public JBIG2SegmentReader(RandomAccessFileOrArray ra ) throws IOException {
		this.ra = ra;
	}

	public static byte[] copyByteArray(byte[] b) {
		byte[] bc = new byte[b.length];
		System.arraycopy(b, 0, bc, 0, b.length);
		return bc;
	}

	public void read() throws IOException {
		if ( this.read ) {
			throw new IllegalStateException(MessageLocalization.getComposedMessage("already.attempted.a.read.on.this.jbig2.file"));
		}
		this.read = true;

		readFileHeader();
		// Annex D
		if ( this.sequential ) {
			// D.1
			do {
				JBIG2Segment tmp = readHeader();
				readSegment(tmp);
				segments.put(Integer.valueOf(tmp.segmentNumber), tmp);
			} while ( this.ra.getFilePointer() < this.ra.length() );
		} else {
			// D.2
			JBIG2Segment tmp;
			do {
				tmp = readHeader();
				segments.put(Integer.valueOf(tmp.segmentNumber), tmp);
			} while ( tmp.type != END_OF_FILE );
			Iterator<Integer> segs = segments.keySet().iterator();
			while ( segs.hasNext() ) {
				readSegment(segments.get(segs.next()));
			}
		}
	}

	void readSegment(JBIG2Segment s) throws IOException {
		int ptr = (int)ra.getFilePointer();

		if ( s.dataLength == 0xffffffffl ) {
			// TODO figure this bit out, 7.2.7
			return;
		}

		byte[] data = new byte[(int)s.dataLength];
		ra.read(data);
		s.data = data;

		if ( s.type == PAGE_INFORMATION ) {
			int last = (int)ra.getFilePointer();
			ra.seek(ptr);
			int page_bitmap_width = ra.readInt();
			int page_bitmap_height = ra.readInt();
			ra.seek(last);
			JBIG2Page p = pages.get(Integer.valueOf(s.page));
			if ( p == null ) {
				throw new IllegalStateException(MessageLocalization.getComposedMessage("referring.to.widht.height.of.page.we.havent.seen.yet.1", s.page));
			}

			p.pageBitmapWidth = page_bitmap_width;
			p.pageBitmapHeight = page_bitmap_height;
		}
	}

	JBIG2Segment readHeader() throws IOException {
		int ptr = (int)ra.getFilePointer();
		// 7.2.1
		int segment_number = ra.readInt();
		JBIG2Segment s = new JBIG2Segment(segment_number);

		// 7.2.3
		int segment_header_flags = ra.read();
		boolean deferred_non_retain = ( segment_header_flags & 0x80 ) == 0x80;
		s.deferredNonRetain = deferred_non_retain;
		boolean page_association_size = ( segment_header_flags & 0x40 ) == 0x40;
		int segment_type = segment_header_flags & 0x3f;
		s.type = segment_type;

		//7.2.4
		int referred_to_byte0 = ra.read();
		int count_of_referred_to_segments = (referred_to_byte0 & 0xE0) >> 5;
		int[] referred_to_segment_numbers = null;
		boolean[] segment_retention_flags = null;

		if ( count_of_referred_to_segments == 7 ) {
			// at least five bytes
			ra.seek(ra.getFilePointer() - 1);
			count_of_referred_to_segments = ra.readInt() & 0x1fffffff;
			segment_retention_flags = new boolean[count_of_referred_to_segments+1];
			int i = 0;
			int referred_to_current_byte = 0;
			do {
				int j = i % 8;
				if ( j == 0) {
					referred_to_current_byte = ra.read();
				}
				segment_retention_flags[i] = (0x1 << j & referred_to_current_byte) >> j == 0x1;
				i++;
			} while ( i <= count_of_referred_to_segments );

		} else if ( count_of_referred_to_segments <= 4 ) {
			// only one byte
			segment_retention_flags = new boolean[count_of_referred_to_segments+1];
			referred_to_byte0 &= 0x1f;
			for ( int i = 0; i <= count_of_referred_to_segments; i++ ) {
				segment_retention_flags[i] = (0x1 << i & referred_to_byte0) >> i == 0x1;
			}

		} else if ( count_of_referred_to_segments == 5 || count_of_referred_to_segments == 6 ) {
			throw new IllegalStateException(MessageLocalization.getComposedMessage("count.of.referred.to.segments.had.bad.value.in.header.for.segment.1.starting.at.2", String.valueOf(segment_number), String.valueOf(ptr)));
		}
		s.segmentRetentionFlags = segment_retention_flags;
		s.countOfReferredToSegments = count_of_referred_to_segments;

		// 7.2.5
		referred_to_segment_numbers = new int[count_of_referred_to_segments+1];
		for ( int i = 1; i <= count_of_referred_to_segments; i++ ) {
			if ( segment_number <= 256 ) {
				referred_to_segment_numbers[i] = ra.read();
			} else if ( segment_number <= 65536 ) {
				referred_to_segment_numbers[i] = ra.readUnsignedShort();
			} else {
				referred_to_segment_numbers[i] = (int)ra.readUnsignedInt(); // TODO wtf ack
			}
		}
		s.referredToSegmentNumbers = referred_to_segment_numbers;

		// 7.2.6
		int segment_page_association;
		int page_association_offset = (int)ra.getFilePointer() - ptr;
		if ( page_association_size ) {
			segment_page_association = ra.readInt();
		} else {
			segment_page_association = ra.read();
		}
		if ( segment_page_association < 0 ) {
			throw new IllegalStateException(MessageLocalization.getComposedMessage("page.1.invalid.for.segment.2.starting.at.3", String.valueOf(segment_page_association), String.valueOf(segment_number), String.valueOf(ptr)));
		}
		s.page = segment_page_association;
		// so we can change the page association at embedding time.
		s.page_association_size = page_association_size;
		s.page_association_offset = page_association_offset;

		if ( segment_page_association > 0 && ! pages.containsKey(Integer.valueOf(segment_page_association)) ) {
			pages.put(Integer.valueOf(segment_page_association), new JBIG2Page(segment_page_association, this));
		}
		if ( segment_page_association > 0 ) {
			pages.get(Integer.valueOf(segment_page_association)).addSegment(s);
		} else {
			globals.add(s);
		}

		// 7.2.7
		long segment_data_length = ra.readUnsignedInt();
		// TODO the 0xffffffff value that might be here, and how to understand those afflicted segments
		s.dataLength = segment_data_length;

		int end_ptr = (int)ra.getFilePointer();
		ra.seek(ptr);
		byte[] header_data = new byte[end_ptr - ptr];
		ra.read(header_data);
		s.headerData  = header_data;

		return s;
	}

	void readFileHeader() throws IOException {
		ra.seek(0);
		byte[] idstring = new byte[8];
		ra.read(idstring);

		byte[] refidstring = {(byte)0x97, 0x4A, 0x42, 0x32, 0x0D, 0x0A, 0x1A, 0x0A};

		for ( int i = 0; i < idstring.length; i++ ) {
			if ( idstring[i] != refidstring[i] ) {
				throw new IllegalStateException(MessageLocalization.getComposedMessage("file.header.idstring.not.good.at.byte.1", i));
			}
		}

		int fileheaderflags = ra.read();

		this.sequential = ( fileheaderflags & 0x1 ) == 0x1;
		this.number_of_pages_known = ( fileheaderflags & 0x2) == 0x0;

		if ( (fileheaderflags & 0xfc) != 0x0 ) {
			throw new IllegalStateException(MessageLocalization.getComposedMessage("file.header.flags.bits.2.7.not.0"));
		}

		if ( this.number_of_pages_known ) {
			this.number_of_pages = ra.readInt();
		}
	}

	public int numberOfPages() {
		return pages.size();
	}

	public int getPageHeight(int i) {
		return pages.get(Integer.valueOf(i)).pageBitmapHeight;
	}

	public int getPageWidth(int i) {
		return pages.get(Integer.valueOf(i)).pageBitmapWidth;
	}

	public JBIG2Page getPage(int page) {
		return pages.get(Integer.valueOf(page));
	}

	public byte[] getGlobal(boolean for_embedding) {
		ByteArrayOutputStream os = new ByteArrayOutputStream();
		try {
			for (Object element : globals) {
				JBIG2Segment s = (JBIG2Segment)element;
				if ( for_embedding &&
						( s.type == END_OF_FILE || s.type == END_OF_PAGE ) ) {
					continue;
				}
				os.write(s.headerData);
				os.write(s.data);
			}
			os.close();
		} catch (IOException e) {
			e.printStackTrace();
		}
		if ( os.size() <= 0 ) {
			return null;
		}
		return os.toByteArray();
	}

	@Override
    public String toString() {
		if ( this.read ) {
			return "Jbig2SegmentReader: number of pages: " + this.numberOfPages();
		} else {
			return "Jbig2SegmentReader in indeterminate state.";
		}
	}
}

⏎ com/itextpdf/text/pdf/codec/JBIG2SegmentReader.java

Or download all of them as a single archive file:

File name: itextpdf-5.5.14-fyi.zip
File size: 2163839 bytes
Release date: 2009-10-09
Download 

⇒ iText-2.1.6.jar - iText, a JAVA-PDF library

⇐ iText layout.jar Source Code

⇑ Download and Install iText Java Library

⇑⇑ iText for PDF Generation