CMapAwareDocumentFont.java

/*
 * Copyright 2008 by Kevin Day.
 *
 * The contents of this file are subject to the Mozilla Public License Version 1.1
 * (the "License"); you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at http://www.mozilla.org/MPL/
 *
 * Software distributed under the License is distributed on an "AS IS" basis,
 * WITHOUT WARRANTY OF ANY KIND, either express or implied. See the License
 * for the specific language governing rights and limitations under the License.
 *
 * The Original Code is 'iText, a free JAVA-PDF library'.
 *
 * The Initial Developer of the Original Code is Bruno Lowagie. Portions created by
 * the Initial Developer are Copyright (C) 1999-2008 by Bruno Lowagie.
 * All Rights Reserved.
 * Co-Developer of the code is Paulo Soares. Portions created by the Co-Developer
 * are Copyright (C) 2000-2008 by Paulo Soares. All Rights Reserved.
 *
 * Contributor(s): all the names of the contributors are added in the source code
 * where applicable.
 *
 * Alternatively, the contents of this file may be used under the terms of the
 * LGPL license (the "GNU LIBRARY GENERAL PUBLIC LICENSE"), in which case the
 * provisions of LGPL are applicable instead of those above.  If you wish to
 * allow use of your version of this file only under the terms of the LGPL
 * License and not to allow others to use your version of this file under
 * the MPL, indicate your decision by deleting the provisions above and
 * replace them with the notice and other provisions required by the LGPL.
 * If you do not delete the provisions above, a recipient may use your version
 * of this file under either the MPL or the GNU LIBRARY GENERAL PUBLIC LICENSE.
 *
 * This library is free software; you can redistribute it and/or modify it
 * under the terms of the MPL as stated above or under the terms of the GNU
 * Library General Public License as published by the Free Software Foundation;
 * either version 2 of the License, or any later version.
 *
 * This library 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 Library general Public License for more
 * details.
 *
 * If you didn't download this code from the following link, you should check if
 * you aren't using an obsolete version:
 * https://github.com/LibrePDF/OpenPDF
 */
package com.lowagie.text.pdf;

import com.lowagie.text.error_messages.MessageLocalization;
import com.lowagie.text.pdf.fonts.cmaps.CMap;
import com.lowagie.text.pdf.fonts.cmaps.CMapParser;

import java.io.ByteArrayInputStream;
import java.io.IOException;

/**
 * Implementation of DocumentFont used while parsing PDF streams.
 * 
 * @since 2.1.4
 */
public class CMapAwareDocumentFont extends DocumentFont {

    /** The font dictionary. */
    private PdfDictionary fontDic;
    /** the width of a space for this font, in normalized 1000 point units */
    private int spaceWidth;
    /**
     * The CMap constructed from the ToUnicode map from the font's dictionary,
     * if present. This CMap transforms CID values into unicode equivalent
     */
    private CMap toUnicodeCmap;
    /**
     * Mapping between CID code (single byte only for now) and unicode
     * equivalent as derived by the font's encoding. Only needed if the
     * ToUnicode CMap is not provided.
     */
    private char[] cidbyte2uni;

    /**
     * Creates an instance of a CMapAwareFont based on an indirect reference to
     * a font.
     * 
     * @param refFont
     *            the indirect reference to a font
     */
    public CMapAwareDocumentFont(PRIndirectReference refFont) {
        super(refFont);
        fontDic = (PdfDictionary) PdfReader.getPdfObjectRelease(refFont);

        processToUnicode();
        if (toUnicodeCmap == null) {
            processUni2Byte();
        }

        spaceWidth = super.getWidth(' ');
        if (spaceWidth == 0) {
            spaceWidth = computeAverageWidth();
        }

    }

    /**
     * Parses the ToUnicode entry, if present, and constructs a CMap for it
     * 
     * @since 2.1.7
     */
    private void processToUnicode() {

        PdfObject toUni = fontDic.get(PdfName.TOUNICODE);
        if (toUni != null) {

            try {
                byte[] touni = PdfReader.getStreamBytes((PRStream) PdfReader
                        .getPdfObjectRelease(toUni));

                CMapParser cmapParser = new CMapParser();
                toUnicodeCmap = cmapParser
                        .parse(new ByteArrayInputStream(touni));
            } catch (IOException e) {
                throw new Error("Unable to process ToUnicode map - "
                        + e.getMessage(), e);
            }
        }
    }

    /**
     * Inverts DocumentFont's uni2byte mapping to obtain a cid-to-unicode
     * mapping based on the font's encoding
     * 
     * @since 2.1.7
     */
    private void processUni2Byte() {
        IntHashtable uni2byte = getUni2Byte();
        int[] e = uni2byte.toOrderedKeys();

        cidbyte2uni = new char[256];
        for (int element : e) {
            int n = uni2byte.get(element);

            // this is messy, messy - an encoding can have multiple unicode
            // values mapping to the same cid - we are going to arbitrarily
            // choose the first one
            // what we really need to do is to parse the encoding, and handle
            // the differences info ourselves. This is a huge duplication of
            // code of what is already
            // being done in DocumentFont, so I really hate to go down that path
            // without seriously thinking about a change in the organization of
            // the Font class hierarchy
            if (cidbyte2uni[n] == 0) {
                cidbyte2uni[n] = (char) element;
            }
        }
    }

    /**
     * For all widths of all glyphs, compute the average width in normalized
     * 1000 point units. This is used to give some meaningful width in cases
     * where we need an average font width (such as if the width of a space
     * isn't specified by a given font)
     * 
     * @return the average width of all non-zero width glyphs in the font
     */
    private int computeAverageWidth() {
        int count = 0;
        int total = 0;
        for (int width : super.widths) {
            if (width != 0) {
                total += width;
                count++;
            }
        }
        return count != 0 ? total / count : 0;
    }

    /**
     * @since 2.1.5 Override to allow special handling for fonts that don't
     *        specify width of space character
     * @see com.lowagie.text.pdf.DocumentFont#getWidth(int)
     */
    @Override
    public int getWidth(int char1) {
        if (char1 == ' ') {
            return spaceWidth;
        }

        return super.getWidth(char1);
    }

    /**
     * Decodes a single CID (represented by one or two bytes) to a unicode
     * String.
     * 
     * @param bytes
     *            the bytes making up the character code to convert
     * @param offset
     *            an offset
     * @param len
     *            a length
     * @return a String containing the encoded form of the input bytes using the
     *         font's encoding.
     */
    private String decodeSingleCID(byte[] bytes, int offset, int len) {
        if (hasUnicodeCMAP()) {
            if (offset + len > bytes.length) {
                throw new ArrayIndexOutOfBoundsException(
                        MessageLocalization.getComposedMessage(
                                "invalid.index.1", offset + len));
            }
            return toUnicodeCmap.lookup(bytes, offset, len);
        }

        if (len == 1) {
            return new String(cidbyte2uni, 0xff & bytes[offset], 1);
        }

        throw new Error("Multi-byte glyphs not implemented yet");
    }

    /**
     * @return true if this font has unicode information available.
     */
    public boolean hasUnicodeCMAP() {
        return toUnicodeCmap != null;
    }

    /**
     * @return true if this font has unicode information available and if it is two bytes.
     */
    public boolean hasTwoByteUnicodeCMAP() {
        return toUnicodeCmap != null && toUnicodeCmap.hasTwoByteMappings();
    }

    /**
     * Decodes a string of bytes (encoded in the font's encoding) into a unicode string. This will
     * use the ToUnicode map of the font, if available, otherwise it uses the font's encoding
     *
     * @param cidbytes the bytes that need to be decoded
     * @param len length
     * @param offset offset
     * @return the unicode String that results from decoding
     * @since 2.1.7
     */
    public String decode(byte[] cidbytes,
                         final int offset,
                         final int len) {
        StringBuilder sb = new StringBuilder(); // it's a shame we can't make this
                                             // StringBuilder
        for (int i = offset; i < offset + len; i++ ) {
            String rslt = decodeSingleCID(cidbytes, i, 1);
            if (rslt == null && i + 1 < offset + len) {
                rslt = decodeSingleCID(cidbytes, i, 2);
                i++ ;
            }
            if (rslt != null) {
                sb.append(rslt);
            }
        }

        return sb.toString();
    }

    /**
     * Decodes a string. This is a normal Java string, but if the range of character values
     * exceeds the range of the encoding for the font, this will fail. Required since we need to
     * process the characters of strings, and we can't determine the character boundaries in
     * advance, especially because of Identity-H encoded fonts which have two-byte character
     * indexes.
     * 
     * PdfString is used to hold character code points, even though the bytes may not map 1-1. It's
     * not possible to change the encoding once a string is in place. 
     * 
     * @param chars
     *            the Characters that need to be decoded
     * @return the unicode String that results from decoding
     * @since 2.1.
     */
    public String decode(String chars) {
        StringBuilder sb = new StringBuilder(); // it's a shame we can't make this
                                             // StringBuilder
        for (char c : chars.toCharArray()) {
            String result = decode(c);
            if (result != null) {
                sb.append(result);
            }
        }

        return sb.toString();
    }

    /**
     * Decode  single character whose value represents a code point in this font. Will fail if
     * the characters do not have values that correspond to valid code points for the font.
     * @param c character to decode
     * @return Unicode character corresponding to the remapped code according to the font's current encoding.
     * @throws Error if the the character is out of range
     */
    public String decode(char c) throws Error {
        String result;
        if (hasUnicodeCMAP()) {
            result = toUnicodeCmap.lookup(c);
        } else if (c <= 0xff) {
            result = new String(cidbyte2uni, 0xff & c, 1);
        } else {
            throw new Error("Multi-byte glyphs not implemented yet");
        }
        return result;
    }

    /**
     * Encodes bytes to a String.
     * 
     * @param bytes
     *            the bytes from a stream
     * @param offset
     *            an offset
     * @param len
     *            a length
     * @return a String encoded taking into account if the bytes are in unicode
     *         or not.
     * @deprecated method name is not indicative of what it does. Use
     *             <code>decode</code> instead.
     */
    @Deprecated
    public String encode(byte[] bytes, int offset, int len) {
        return decode(bytes, offset, len);
    }
}