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PDF renderer implementation supporting the subset of PDF 1.4 specification.
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/*
* $Id: PDFFontEncoding.java,v 1.4 2009/02/12 13:53:54 tomoke Exp $
*
* Copyright 2004 Sun Microsystems, Inc., 4150 Network Circle,
* Santa Clara, California 95054, U.S.A. All rights reserved.
*
* This library is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public
* License as published by the Free Software Foundation; either
* version 2.1 of the License, or (at your option) 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
* Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public
* License along with this library; if not, write to the Free Software
* Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
*/
package com.sun.pdfview.font;
import java.io.IOException;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import com.sun.pdfview.PDFObject;
/**
* The PDFFont encoding encapsulates the mapping from character codes
* in the PDF document to glyphs of the font.
*
* Encodings take two basic forms. For Type1, TrueType, and Type3 fonts,
* the encoding maps from character codes to Strings, which represent the
* glyphs of the font. For Type0 fonts, the mapping is a CMap which maps
* character codes to characters in one of many descendant fonts.
*
* Note that the data in the PDF might be ASCII characters (bytes) or it might
* be a multi-byte format such as unicode. For now we will assume all
* glyph ids fit into at most the two bytes of a character.
*/
public class PDFFontEncoding {
/** Encoding types */
private static final int TYPE_ENCODING = 0;
private static final int TYPE_CMAP = 1;
/**
* the base encoding (an array of integers which can be mapped to names
* using the methods on FontSupport
*/
private int[] baseEncoding;
/** any differences from the base encoding */
private Map differences;
/**
* a CMap for fonts encoded by CMap
*/
private PDFCMap cmap;
/**
* the type of this encoding (encoding or CMap)
*/
private int type;
/** Creates a new instance of PDFFontEncoding */
public PDFFontEncoding(String fontType, PDFObject encoding)
throws IOException {
if (encoding.getType() == PDFObject.NAME) {
// if the encoding is a String, it is the name of an encoding
// or the name of a CMap, depending on the type of the font
if (fontType.equals("Type0")) {
type = TYPE_CMAP;
cmap = PDFCMap.getCMap(encoding.getStringValue());
} else {
type = TYPE_ENCODING;
differences = new HashMap();
baseEncoding = this.getBaseEncoding(encoding.getStringValue());
}
} else {
// loook at the "Type" entry of the encoding to determine the type
String typeStr = encoding.getDictRef("Type").getStringValue();
if (typeStr.equals("Encoding")) {
// it is an encoding
type = TYPE_ENCODING;
parseEncoding(encoding);
} else if (typeStr.equals("CMap")) {
// it is a CMap
type = TYPE_CMAP;
cmap = PDFCMap.getCMap(encoding);
} else {
throw new IllegalArgumentException("Uknown encoding type: " + type);
}
}
}
/** Get the glyphs associated with a given String */
public List getGlyphs(PDFFont font, String text) {
List outList = new ArrayList(text.length());
// go character by character through the text
char[] arry = text.toCharArray();
for (int i = 0; i < arry.length; i++) {
switch (type) {
case TYPE_ENCODING:
outList.add(getGlyphFromEncoding(font, arry[i]));
break;
case TYPE_CMAP:
// 2 bytes -> 1 character in a CMap
char c = (char) ((arry[i] & 0xff) << 8);
if (i < arry.length - 1) {
c |= (char) (arry[++i] & 0xff);
}
outList.add(getGlyphFromCMap(font, c));
break;
}
}
return outList;
}
/**
* Get a glyph from an encoding, given a font and character
*/
private PDFGlyph getGlyphFromEncoding(PDFFont font, char src) {
String charName = null;
// only deal with one byte of source
src &= 0xff;
// see if this character is in the differences list
if (differences.containsKey(new Character(src))) {
charName = (String) differences.get(new Character(src));
} else if (baseEncoding != null) {
// get the character name from the base encoding
int charID = baseEncoding[src];
charName = FontSupport.getName(charID);
}
return font.getCachedGlyph(src, charName);
}
/**
* Get a glyph from a CMap, given a Type0 font and a character
*/
private PDFGlyph getGlyphFromCMap(PDFFont font, char src) {
int fontID = cmap.getFontID(src);
char charID = cmap.map(src);
if (font instanceof Type0Font) {
font = ((Type0Font) font).getDescendantFont(fontID);
}
return font.getCachedGlyph(charID, null);
}
/**
* Parse a PDF encoding object for the actual encoding
*/
public void parseEncoding(PDFObject encoding) throws IOException {
differences = new HashMap();
// figure out the base encoding, if one exists
PDFObject baseEncObj = encoding.getDictRef("BaseEncoding");
if (baseEncObj != null) {
baseEncoding = getBaseEncoding(baseEncObj.getStringValue());
}
// parse the differences array
PDFObject diffArrayObj = encoding.getDictRef("Differences");
if (diffArrayObj != null) {
PDFObject[] diffArray = diffArrayObj.getArray();
int curPosition = -1;
for (int i = 0; i < diffArray.length; i++) {
if (diffArray[i].getType() == PDFObject.NUMBER) {
curPosition = diffArray[i].getIntValue();
} else if (diffArray[i].getType() == PDFObject.NAME) {
Character key = new Character((char) curPosition);
differences.put(key, diffArray[i].getStringValue());
curPosition++;
} else {
throw new IllegalArgumentException("Unexpected type in diff array: " + diffArray[i]);
}
}
}
}
/** Get the base encoding for a given name */
private int[] getBaseEncoding(String encodingName) {
if (encodingName.equals("MacRomanEncoding")) {
return FontSupport.macRomanEncoding;
} else if (encodingName.equals("MacExpertEncoding")) {
return FontSupport.type1CExpertCharset;
} else if (encodingName.equals("WinAnsiEncoding")) {
return FontSupport.winAnsiEncoding;
} else {
throw new IllegalArgumentException("Unknown encoding: " + encodingName);
}
}
}