David Kuettel
84 lines
2.5 KiB
Java
84 lines
2.5 KiB
Java
// Copyright 2011 Google Inc. All rights reserved.
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// Use of this source code is governed by a BSD-style license that can be
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// found in the LICENSE file.
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package com.google.typography.font.compression;
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import com.google.common.collect.Lists;
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import com.google.common.collect.Maps;
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import com.google.typography.font.sfntly.Font;
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import com.google.typography.font.sfntly.Tag;
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import com.google.typography.font.sfntly.table.core.CMap;
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import com.google.typography.font.sfntly.table.core.CMapTable;
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import com.google.typography.font.sfntly.table.core.MaximumProfileTable;
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import java.io.ByteArrayOutputStream;
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import java.util.List;
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import java.util.Map;
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/**
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* Experimental CMap encoder, based primarily on writing the _inverse_ encoding.
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*
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* @author raph@google.com (Raph Levien)
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*/
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public class CmapEncoder {
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public static byte[] encode(Font font) {
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int nGlyphs = font.<MaximumProfileTable>getTable(Tag.maxp).numGlyphs();
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CMapTable cmapTable = font.getTable(Tag.cmap);
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CMap cmap = getBestCMap(cmapTable);
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Map<Integer, Integer> invEncoding = Maps.newHashMap();
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List<Integer> exceptions = Lists.newArrayList();
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for (Integer i : cmap) {
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int glyphId = cmap.glyphId(i);
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if (invEncoding.containsKey(glyphId)) {
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exceptions.add(i);
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exceptions.add(glyphId);
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} else {
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invEncoding.put(glyphId, i);
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}
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}
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ByteArrayOutputStream os = new ByteArrayOutputStream();
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int last = -1;
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for (int i = 0; i < nGlyphs; i++) {
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if (invEncoding.containsKey(i)) {
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int value = invEncoding.get(i);
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int delta = value - last;
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writeVShort(os, delta);
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last = value;
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} else {
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writeVShort(os, 0);
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}
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}
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for (int i : exceptions) {
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writeVShort(os, i);
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}
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return os.toByteArray();
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}
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private static CMap getBestCMap(CMapTable cmapTable) {
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for (CMap cmap : cmapTable) {
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if (cmap.format() == CMap.CMapFormat.Format12.value()) {
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return cmap;
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}
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}
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for (CMap cmap : cmapTable) {
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if (cmap.format() == CMap.CMapFormat.Format4.value()) {
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return cmap;
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}
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}
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return null;
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}
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// A simple signed varint encoding
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static void writeVShort(ByteArrayOutputStream os, int value) {
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if (value >= 0x2000 || value < -0x2000) {
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os.write((byte)(0x80 | ((value >> 14) & 0x7f)));
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}
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if (value >= 0x40 || value < -0x40) {
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os.write((byte)(0x80 | ((value >> 7) & 0x7f)));
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}
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os.write((byte)(value & 0x7f));
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}
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}
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