jpeghuffmantable.java

java1.6众多例子参考

/*
 * @(#)JPEGHuffmanTable.java	1.11 05/11/17
 *
 * Copyright 2006 Sun Microsystems, Inc. All rights reserved.
 * SUN PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
 */

/**********************************************************************
 **********************************************************************
 **********************************************************************
 *** COPYRIGHT (c) 1997-1998 Eastman Kodak Company.                 ***
 *** As  an unpublished  work pursuant to Title 17 of the United    ***
 *** States Code.  All rights reserved.                             ***
 **********************************************************************
 **********************************************************************
 **********************************************************************/

package com.sun.image.codec.jpeg;


/** A class to encapsulate a JPEG Huffman table.
 * <p>
 * Note that the classes in the com.sun.image.codec.jpeg package are not
 * part of the core Java APIs.  They are a part of Sun's JDK and JRE
 * distributions.  Although other licensees may choose to distribute these
 * classes, developers cannot depend on their availability in non-Sun
 * implementations.  We expect that equivalent functionality will eventually
 * be available in a core API or standard extension.
 * <p>
 */
public class JPEGHuffmanTable {

	/** 
	 * The maximum number of symbol lengths
	 * (max symbol length in bits = 16) 
	 */
    private static final int HUFF_MAX_LEN=17;
	
    /** the maximum number of symbols */
    private static final int HUFF_MAX_SYM=256;
	
    /** bits[k] = number of symbols with length k bits	*/
    private short lengths[];
	
    /** Symbols in order of increasing length */
    private short symbols[];
	
    /** Standard Huffman table ( JPEG standard section K.3 ) */
	public static final JPEGHuffmanTable StdDCLuminance = 
		new JPEGHuffmanTable();

	static {
		short lengths[] = { // 0-base
			0, 0, 1, 5, 1, 1, 1, 1, 1, 1, 0, 0, 0, 0, 0, 0, 0 };
		short symbols[] = {
			0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11 };
		
		StdDCLuminance.lengths = lengths;
		StdDCLuminance.symbols = symbols;
		StdDCLuminance.checkTable();
	}
	
	
    /** Standard Huffman table ( JPEG standard section K.3 ) */
	public static final JPEGHuffmanTable StdDCChrominance = 
		new JPEGHuffmanTable();
	static {
		short lengths[] = { // 0-base
			0, 0, 3, 1, 1, 1, 1, 1, 1, 1, 1, 1, 0, 0, 0, 0, 0 };
		short symbols[] = {
			0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11 };
		
		StdDCChrominance.lengths = lengths;
		StdDCChrominance.symbols = symbols;
		StdDCChrominance.checkTable();
	}
	
	/** Standard Huffman table ( JPEG standard section K.3 ) */
	public static final JPEGHuffmanTable StdACLuminance = 
		new JPEGHuffmanTable();
	static {
		short lengths[] = { // 0-base
			0, 0, 2, 1, 3, 3, 2, 4, 3, 5, 5, 4, 4, 0, 0, 1, 0x7d };
		short symbols[] = { 
			0x01, 0x02, 0x03, 0x00, 0x04, 0x11, 0x05, 0x12,
			0x21, 0x31, 0x41, 0x06, 0x13, 0x51, 0x61, 0x07,
			0x22, 0x71, 0x14, 0x32, 0x81, 0x91, 0xa1, 0x08,
			0x23, 0x42, 0xb1, 0xc1, 0x15, 0x52, 0xd1, 0xf0,
			0x24, 0x33, 0x62, 0x72, 0x82, 0x09, 0x0a, 0x16,
			0x17, 0x18, 0x19, 0x1a, 0x25, 0x26, 0x27, 0x28,
			0x29, 0x2a, 0x34, 0x35, 0x36, 0x37, 0x38, 0x39,
			0x3a, 0x43, 0x44, 0x45, 0x46, 0x47, 0x48, 0x49,
			0x4a, 0x53, 0x54, 0x55, 0x56, 0x57, 0x58, 0x59,
			0x5a, 0x63, 0x64, 0x65, 0x66, 0x67, 0x68, 0x69,
			0x6a, 0x73, 0x74, 0x75, 0x76, 0x77, 0x78, 0x79,
			0x7a, 0x83, 0x84, 0x85, 0x86, 0x87, 0x88, 0x89,
			0x8a, 0x92, 0x93, 0x94, 0x95, 0x96, 0x97, 0x98,
			0x99, 0x9a, 0xa2, 0xa3, 0xa4, 0xa5, 0xa6, 0xa7,
			0xa8, 0xa9, 0xaa, 0xb2, 0xb3, 0xb4, 0xb5, 0xb6,
			0xb7, 0xb8, 0xb9, 0xba, 0xc2, 0xc3, 0xc4, 0xc5,
			0xc6, 0xc7, 0xc8, 0xc9, 0xca, 0xd2, 0xd3, 0xd4,
			0xd5, 0xd6, 0xd7, 0xd8, 0xd9, 0xda, 0xe1, 0xe2,
			0xe3, 0xe4, 0xe5, 0xe6, 0xe7, 0xe8, 0xe9, 0xea,
			0xf1, 0xf2, 0xf3, 0xf4, 0xf5, 0xf6, 0xf7, 0xf8,
			0xf9, 0xfa };
			
		StdACLuminance.lengths = lengths;
		StdACLuminance.symbols = symbols;
		StdACLuminance.checkTable();
	}
	
    /** Standard Huffman table ( JPEG standard section K.3 ) */
	public static final JPEGHuffmanTable StdACChrominance = 
		new JPEGHuffmanTable();
	static {
		short lengths[] =  { // 0-base
			0, 0, 2, 1, 2, 4, 4, 3, 4, 7, 5, 4, 4, 0, 1, 2, 0x77 };
		short symbols[] = { 
			0x00, 0x01, 0x02, 0x03, 0x11, 0x04, 0x05, 0x21,
			0x31, 0x06, 0x12, 0x41, 0x51, 0x07, 0x61, 0x71,
			0x13, 0x22, 0x32, 0x81, 0x08, 0x14, 0x42, 0x91,
			0xa1, 0xb1, 0xc1, 0x09, 0x23, 0x33, 0x52, 0xf0,
			0x15, 0x62, 0x72, 0xd1, 0x0a, 0x16, 0x24, 0x34,
			0xe1, 0x25, 0xf1, 0x17, 0x18, 0x19, 0x1a, 0x26,
			0x27, 0x28, 0x29, 0x2a, 0x35, 0x36, 0x37, 0x38,
			0x39, 0x3a, 0x43, 0x44, 0x45, 0x46, 0x47, 0x48,
			0x49, 0x4a, 0x53, 0x54, 0x55, 0x56, 0x57, 0x58,
			0x59, 0x5a, 0x63, 0x64, 0x65, 0x66, 0x67, 0x68,
			0x69, 0x6a, 0x73, 0x74, 0x75, 0x76, 0x77, 0x78,
			0x79, 0x7a, 0x82, 0x83, 0x84, 0x85, 0x86, 0x87,
			0x88, 0x89, 0x8a, 0x92, 0x93, 0x94, 0x95, 0x96,
			0x97, 0x98, 0x99, 0x9a, 0xa2, 0xa3, 0xa4, 0xa5,
			0xa6, 0xa7, 0xa8, 0xa9, 0xaa, 0xb2, 0xb3, 0xb4,
			0xb5, 0xb6, 0xb7, 0xb8, 0xb9, 0xba, 0xc2, 0xc3,
			0xc4, 0xc5, 0xc6, 0xc7, 0xc8, 0xc9, 0xca, 0xd2,
			0xd3, 0xd4, 0xd5, 0xd6, 0xd7, 0xd8, 0xd9, 0xda,
			0xe2, 0xe3, 0xe4, 0xe5, 0xe6, 0xe7, 0xe8, 0xe9,
			0xea, 0xf2, 0xf3, 0xf4, 0xf5, 0xf6, 0xf7, 0xf8,
			0xf9, 0xfa };
			
		StdACChrominance.lengths = lengths;
		StdACChrominance.symbols = symbols;
		StdACChrominance.checkTable();
	}
	
	/**
	 * Private constructor used to construct the Standard Huffman tables
	 */
    private JPEGHuffmanTable() {
		lengths = null;
		symbols = null;
	}

    /** 
     * Creates a Huffman Table and initializes it.
     * @param lengths lengths[k] = # of symbols with codes of length k
     * bits; lengths[0] is ignored
     * @param symbols symbols in order of increasing code length
     * @exception IllegalArgumentException if the length of 
     * <code>lengths</code> is greater than 17
     * @exception IllegalArgumentException if the length of
     * <code>symbols</code> is greater than 256
     * @exception IllegalArgumentException if any of the values in 
     * <code>lengths</code> or <code>symbols</code> is less than zero
     */
    public JPEGHuffmanTable( short lengths[], short symbols[] ) {
		if ( lengths.length > HUFF_MAX_LEN )
			throw new IllegalArgumentException( "lengths array is too long" );
		for (int i=1; i < lengths.length; i++)
			if (lengths[i] < 0)
				throw new IllegalArgumentException
					( "Values in lengths array must be non-negative." );

		
		if ( symbols.length > HUFF_MAX_SYM )
			throw new IllegalArgumentException( "symbols array is too long" );
		for (int i=0; i < symbols.length; i++)
			if (symbols[i] < 0)
				throw new IllegalArgumentException
					( "Values in symbols array must be non-negative." );
		
		this.lengths = new short[lengths.length];
		this.symbols = new short[symbols.length];
		
		System.arraycopy( lengths, 0, this.lengths, 0, lengths.length );
		System.arraycopy( symbols, 0, this.symbols, 0, symbols.length );

		checkTable();
    }

	/**
	 * This checks that the table they gave us isn't 'illegal' It
	 * checks that the symbol length counts are possible, and that
	 * they gave us at least enough symbols for the symbol length
	 * counts. Eventually this might check that there aren't duplicate
	 * symbols.
	 */
	private void checkTable() {
		int numVals=2;
		int sum=0;
		for (int i=1; i<lengths.length; i++) {
			sum     += lengths[i];
			numVals -= lengths[i];
			numVals *= 2;
		}

		//System.out.println("NumVals: " + numVals);
		//System.out.println("Sum: " + sum + " Symbols: " + symbols.length);

		if (numVals < 0) 
			throw new IllegalArgumentException
				("Invalid Huffman Table provided, lengths are incorrect.");

		// I'll let them go if they gave us 'extra' symbols...
		if (sum > symbols.length)
			throw new IllegalArgumentException
				("Invalid Huffman Table provided, not enough symbols.");
	}

	/** 
	 * Return a copy of the array containing the number of symbols
	 * for each length in the Huffman table.
	 * @return A short array where array[k] = # of symbols in the
	 *         table of length k. array[0] is unused
	 */
    public short[] getLengths() {
		short[] ret = new short[ lengths.length];
		System.arraycopy( lengths, 0, ret, 0, lengths.length);
		return ret;
    }

    /** 
	 * Return an array containing the Huffman symbols arranged by
	 * increasing length.  To make use of this array you must refer
	 * the the lengths array.
	 * @return A short array of Huffman symbols
     */
    public short[] getSymbols() {
		short[] ret = new short[symbols.length];
		System.arraycopy( symbols, 0, ret, 0, symbols.length);
		return ret;
    }
}