jpeghuffmantable.java

源码为Eclipse开源开发平台桌面开发工具SWT的源代码,

/*******************************************************************************
 * Copyright (c) 2000, 2003 IBM Corporation and others.
 * All rights reserved. This program and the accompanying materials 
 * are made available under the terms of the Common Public License v1.0
 * which accompanies this distribution, and is available at
 * http://www.eclipse.org/legal/cpl-v10.html
 * 
 * Contributors:
 *     IBM Corporation - initial API and implementation
 *******************************************************************************/
package org.eclipse.swt.internal.image;


/**
 * JPEGHuffmanTable class actually represents two types of object:
 * 1) A DHT (Define Huffman Tables) segment, which may represent
 *	as many as 4 Huffman tables. In this case, the tables are
 *	stored in the allTables array.
 * 2) A single Huffman table. In this case, the allTables array
 *	will be null.
 * The 'reference' field is stored in both types of object, but
 * 'initialize' is only called if the object represents a DHT.
 */
final class JPEGHuffmanTable extends JPEGVariableSizeSegment {
	JPEGHuffmanTable[] allTables;
	int tableClass;
	int tableIdentifier;
	int[] dhCodes;
	int[] dhCodeLengths;
	int[] dhMaxCodes;
	int[] dhMinCodes;
	int[] dhValPtrs;
	int[] dhValues;
	int[] ehCodes;
	byte[] ehCodeLengths;
	static byte[] DCLuminanceTable = {
		(byte)255, (byte)196, 0, 31, 0, 0, 1, 5, 1, 1, 1, 1, 1, 1, 0, 0, 0, 0, 0, 0, 0,
		0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11
	};
	static byte[] DCChrominanceTable = {
		(byte)255, (byte)196, 0, 31, 1, 0, 3, 1, 1, 1, 1, 1, 1, 1, 1, 1, 0, 0, 0, 0, 0,
		0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11
	};
	static byte[] ACLuminanceTable = {
		(byte)255, (byte)196, 0, (byte)181, 16, 0, 2, 1, 3, 3, 2, 4, 3, 5, 5, 4, 4, 0, 0, 1, 125, 
		1, 2, 3, 0, 4, 17, 5, 18, 33, 49, 65, 6, 19, 81, 97, 7, 34, 113, 20, 
		50, (byte)129, (byte)145, (byte)161, 8, 35, 66, (byte)177, (byte)193, 21, 82, (byte)209, (byte)240, 36, 51, 98, 
		114, (byte)130, 9, 10, 22, 23, 24, 25, 26, 37, 38, 39, 40, 41, 42, 52, 53, 
		54, 55, 56, 57, 58, 67, 68, 69, 70, 71, 72, 73, 74, 83, 84, 85, 86, 87, 
		88, 89, 90, 99, 100, 101, 102, 103, 104, 105, 106, 115, 116, 117, 118, 
		119, 120, 121, 122, (byte)131, (byte)132, (byte)133, (byte)134, (byte)135, (byte)136, (byte)137, (byte)138, (byte)146, (byte)147, (byte)148, 
		(byte)149, (byte)150, (byte)151, (byte)152, (byte)153, (byte)154, (byte)162, (byte)163, (byte)164, (byte)165, (byte)166, (byte)167, (byte)168, (byte)169, (byte)170, 
		(byte)178, (byte)179, (byte)180, (byte)181, (byte)182, (byte)183, (byte)184, (byte)185, (byte)186, (byte)194, (byte)195, (byte)196, (byte)197, (byte)198, (byte)199, 
		(byte)200, (byte)201, (byte)202, (byte)210, (byte)211, (byte)212, (byte)213, (byte)214, (byte)215, (byte)216, (byte)217, (byte)218, (byte)225, (byte)226, (byte)227, 
		(byte)228, (byte)229, (byte)230, (byte)231, (byte)232, (byte)233, (byte)234, (byte)241, (byte)242, (byte)243, (byte)244, (byte)245, (byte)246, (byte)247, (byte)248, 
		(byte)249, (byte)250
	};
	static byte[] ACChrominanceTable = {
		(byte)255, (byte)196, 0, (byte)181, 17, 0, 2, 1, 2, 4, 4, 3, 4, 7, 5, 4, 4, 0, 
		1, 2, 119, 0, 1, 2, 3, 17, 4, 5, 33, 49, 6, 18, 65, 81, 7, 97, 113, 19, 34, 
		50, (byte)129, 8, 20, 66, (byte)145, (byte)161, (byte)177, (byte)193, 9, 35, 
		51, 82, (byte)240, 21, 98, 114, (byte)209, 10, 22, 36, 52, (byte)225, 37, 
		(byte)241, 23, 24, 25, 26, 38, 39, 40, 41, 42, 53, 54, 55, 56, 57, 58, 67, 
		68, 69, 70, 71, 72, 73, 74, 83, 84, 85, 86, 87, 88, 89, 90, 99, 100, 101, 102, 
		103, 104, 105, 106, 115, 116, 117, 118, 119, 120, 121, 122, (byte)130, 
		(byte)131, (byte)132, (byte)133, (byte)134, (byte)135, (byte)136, (byte)137, 
		(byte)138, (byte)146, (byte)147, (byte)148, (byte)149, (byte)150, (byte)151, 
		(byte)152, (byte)153, (byte)154, (byte)162, (byte)163, (byte)164, (byte)165, 
		(byte)166, (byte)167, (byte)168, (byte)169, (byte)170, (byte)178, (byte)179, 
		(byte)180, (byte)181, (byte)182, (byte)183, (byte)184, (byte)185, (byte)186, 
		(byte)194, (byte)195, (byte)196, (byte)197, (byte)198, (byte)199, (byte)200, 
		(byte)201, (byte)202, (byte)210, (byte)211, (byte)212, (byte)213, (byte)214, 
		(byte)215, (byte)216, (byte)217, (byte)218, (byte)226, (byte)227, (byte)228, 
		(byte)229, (byte)230, (byte)231, (byte)232, (byte)233, (byte)234, (byte)242, 
		(byte)243, (byte)244, (byte)245, (byte)246, (byte)247, (byte)248, (byte)249, 
		(byte)250
	};
	
public JPEGHuffmanTable(byte[] reference) {
	super(reference);
}

public JPEGHuffmanTable(LEDataInputStream byteStream) {
	super(byteStream);
	initialize();
}

public JPEGHuffmanTable[] getAllTables() {
	return allTables;
}

public static JPEGHuffmanTable getDefaultACChrominanceTable() {
	JPEGHuffmanTable result = new JPEGHuffmanTable(ACChrominanceTable);
	result.initialize();
	return result;
}

public static JPEGHuffmanTable getDefaultACLuminanceTable() {
	JPEGHuffmanTable result = new JPEGHuffmanTable(ACLuminanceTable);
	result.initialize();
	return result;
}

public static JPEGHuffmanTable getDefaultDCChrominanceTable() {
	JPEGHuffmanTable result = new JPEGHuffmanTable(DCChrominanceTable);
	result.initialize();
	return result;
}

public static JPEGHuffmanTable getDefaultDCLuminanceTable() {
	JPEGHuffmanTable result = new JPEGHuffmanTable(DCLuminanceTable);
	result.initialize();
	return result;
}

public int[] getDhMaxCodes() {
	return dhMaxCodes;
}

public int[] getDhMinCodes() {
	return dhMinCodes;
}

public int[] getDhValPtrs() {
	return dhValPtrs;
}

public int[] getDhValues() {
	return dhValues;
}

public int getTableClass() {
	return tableClass;
}

public int getTableIdentifier() {
	return tableIdentifier;
}

void initialize() {
	int totalLength = getSegmentLength() - 2;
	int ofs = 4;
	int[] bits = new int[16];
	JPEGHuffmanTable[] huffTables = new JPEGHuffmanTable[8]; // maximum is 4 AC + 4 DC
	int huffTableCount = 0;
	while (totalLength > 0) {
		int tc = (reference[ofs] & 0xFF) / 16; // table class: AC (1) or DC (0)
		int tid = (reference[ofs] & 0xFF) % 16; // table id: 0-1 baseline, 0-3 prog/ext
		ofs++;
		
		/* Read the 16 count bytes and add them together to get the table size. */
		int count = 0;
		for (int i = 0; i < bits.length; i++) {
			int bCount = reference[ofs + i] & 0xFF;
			bits[i] = bCount;
			count += bCount;
		}
		ofs += 16;
		totalLength -= 17;
		
		/* Read the table. */
		int[] huffVals = new int[count];
		for (int i = 0; i < count; i++) {
			huffVals[i] = reference[ofs + i] & 0xFF;
		}
		ofs += count;
		totalLength -= count;
		
		/* Calculate the lengths. */
		int[] huffCodeLengths = new int[50]; // start with 50 and increment as needed
		int huffCodeLengthsIndex = 0;
		for (int i = 0; i < 16; i++) {
			for (int j = 0; j < bits[i]; j++) {
				if (huffCodeLengthsIndex >= huffCodeLengths.length) {
					int[] newHuffCodeLengths = new int[huffCodeLengths.length + 50];
					System.arraycopy(huffCodeLengths, 0, newHuffCodeLengths, 0, huffCodeLengths.length);
					huffCodeLengths = newHuffCodeLengths;
				}
				huffCodeLengths[huffCodeLengthsIndex] = i + 1;
				huffCodeLengthsIndex++;
			}
		}
		
		/* Truncate huffCodeLengths to the correct size. */
		if (huffCodeLengthsIndex < huffCodeLengths.length) {
			int[] newHuffCodeLengths = new int[huffCodeLengthsIndex];
			System.arraycopy(huffCodeLengths, 0, newHuffCodeLengths, 0, huffCodeLengthsIndex);
			huffCodeLengths = newHuffCodeLengths;
		}
		
		/* Calculate the Huffman codes. */
		int[] huffCodes = new int[50]; // start with 50 and increment as needed
		int huffCodesIndex = 0;
		int k = 1;
		int code = 0;
		int si = huffCodeLengths[0];
		int p = 0;
		while (p < huffCodeLengthsIndex) {
			while ((p < huffCodeLengthsIndex) && (huffCodeLengths[p] == si)) {
				if (huffCodesIndex >= huffCodes.length) {
					int[] newHuffCodes = new int[huffCodes.length + 50];
					System.arraycopy(huffCodes, 0, newHuffCodes, 0, huffCodes.length);
					huffCodes = newHuffCodes;
				}
				huffCodes[huffCodesIndex] = code;
				huffCodesIndex++;
				code++;
				p++;
			}
			code *= 2;
			si++;
		}
		
		/* Truncate huffCodes to the correct size. */
		if (huffCodesIndex < huffCodes.length) {
			int[] newHuffCodes = new int[huffCodesIndex];
			System.arraycopy(huffCodes, 0, newHuffCodes, 0, huffCodesIndex);
			huffCodes = newHuffCodes;
		}
		
		/* Calculate the maximum and minimum codes */
		k = 0;
		int[] maxCodes = new int[16];
		int[] minCodes = new int[16];
		int[] valPtrs = new int[16];
		for (int i = 0; i < 16; i++) {
			int bSize = bits[i];
			if (bSize == 0) {
				maxCodes[i] = -1;
			} else {
				valPtrs[i] = k;
				minCodes[i] = huffCodes[k];
				k += bSize;
				maxCodes[i] = huffCodes[k - 1];
			}
		}
		
		/* Calculate the eHuffman codes and lengths. */
		int[] eHuffCodes = new int[256];
		byte[] eHuffSize = new byte[256];
		for (int i = 0; i < huffCodesIndex; i++) {
			eHuffCodes[huffVals[i]] = huffCodes[i];
			eHuffSize[huffVals[i]] = (byte)huffCodeLengths[i];
		}
		
		/* Create the new JPEGHuffmanTable and add it to the allTables array. */
		JPEGHuffmanTable dhtTable = new JPEGHuffmanTable(reference);
		dhtTable.tableClass = tc;
		dhtTable.tableIdentifier = tid;
		dhtTable.dhValues = huffVals;
		dhtTable.dhCodes = huffCodes;
		dhtTable.dhCodeLengths = huffCodeLengths;
		dhtTable.dhMinCodes = minCodes;
		dhtTable.dhMaxCodes = maxCodes;
		dhtTable.dhValPtrs = valPtrs;
		dhtTable.ehCodes = eHuffCodes;
		dhtTable.ehCodeLengths = eHuffSize;
		huffTables[huffTableCount] = dhtTable;
		huffTableCount++;
	}
	allTables = new JPEGHuffmanTable[huffTableCount];
	System.arraycopy(huffTables, 0, allTables, 0, huffTableCount);
}

public int signature() {
	return JPEGFileFormat.DHT;
}
}