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package javax.imageio.plugins.jpeg;

import java.util.Arrays;


A class encapsulating a single JPEG Huffman table.
Fields are provided for the "standard" tables taken
from Annex K of the JPEG specification.
These are the tables used as defaults.


For more information about the operation of the standard JPEG plug-in,
see the JPEG
metadata format specification and usage notes

/**
 * A class encapsulating a single JPEG Huffman table.
 * Fields are provided for the "standard" tables taken
 * from Annex K of the JPEG specification.
 * These are the tables used as defaults.
 * <p>
 * For more information about the operation of the standard JPEG plug-in,
 * see the <A HREF="../../metadata/doc-files/jpeg_metadata.html">JPEG
 * metadata format specification and usage notes</A>
 */

public class JPEGHuffmanTable {

    /* The data for the publically defined tables, as specified in ITU T.81
     * JPEG specification section K3.3 and used in the IJG library.
     */
    private static final short[] StdDCLuminanceLengths = {
        0x00, 0x01, 0x05, 0x01, 0x01, 0x01, 0x01, 0x01,
        0x01, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
    };

    private static final short[] StdDCLuminanceValues = {
        0x00, 0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07,
        0x08, 0x09, 0x0a, 0x0b,
    };

    private static final short[] StdDCChrominanceLengths = {
        0x00, 0x03, 0x01, 0x01, 0x01, 0x01, 0x01, 0x01,
        0x01, 0x01, 0x01, 0x00, 0x00, 0x00, 0x00, 0x00,
    };

    private static final short[] StdDCChrominanceValues = {
        0x00, 0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07,
        0x08, 0x09, 0x0a, 0x0b,
    };

    private static final short[] StdACLuminanceLengths = {
        0x00, 0x02, 0x01, 0x03, 0x03, 0x02, 0x04, 0x03,
        0x05, 0x05, 0x04, 0x04, 0x00, 0x00, 0x01, 0x7d,
    };

    private static final short[] StdACLuminanceValues = {
        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,
    };

    private static final short[] StdACChrominanceLengths = {
        0x00, 0x02, 0x01, 0x02, 0x04, 0x04, 0x03, 0x04,
        0x07, 0x05, 0x04, 0x04, 0x00, 0x01, 0x02, 0x77,
    };

    private static final short[] StdACChrominanceValues = {
        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,
    };

    
The standard DC luminance Huffman table.

/**
     * The standard DC luminance Huffman table.
     */
    public static final JPEGHuffmanTable
        StdDCLuminance = new JPEGHuffmanTable(StdDCLuminanceLengths,
                                              StdDCLuminanceValues, false);

    
The standard DC chrominance Huffman table.

/**
     * The standard DC chrominance Huffman table.
     */
    public static final JPEGHuffmanTable
        StdDCChrominance = new JPEGHuffmanTable(StdDCChrominanceLengths,
                                                StdDCChrominanceValues, false);

    
The standard AC luminance Huffman table.

/**
     * The standard AC luminance Huffman table.
     */
    public static final JPEGHuffmanTable
        StdACLuminance = new JPEGHuffmanTable(StdACLuminanceLengths,
                                              StdACLuminanceValues, false);

    
The standard AC chrominance Huffman table.

/**
     * The standard AC chrominance Huffman table.
     */
    public static final JPEGHuffmanTable
        StdACChrominance = new JPEGHuffmanTable(StdACChrominanceLengths,
                                                StdACChrominanceValues, false);

    private short[] lengths;
    private short[] values;

    
Creates a Huffman table and initializes it. The input arrays are copied.
The arrays must describe a possible Huffman table.
For example, 3 codes cannot be expressed with a single bit.

Params:
  • lengths – an array of shorts where lengths[k] is equal to the number of values with corresponding codes of length k + 1 bits.
  • values – an array of shorts containing the values in
order of increasing code length.
Throws:
  • IllegalArgumentException – if lengths or values are null, the length of lengths is greater than 16, the length of values is greater than 256, if any value in lengths or values is less than zero, or if the arrays do not describe a valid Huffman table.
/**
     * Creates a Huffman table and initializes it. The input arrays are copied.
     * The arrays must describe a possible Huffman table.
     * For example, 3 codes cannot be expressed with a single bit.
     *
     * @param lengths an array of {@code short}s where {@code lengths[k]}
     * is equal to the number of values with corresponding codes of
     * length {@code k + 1} bits.
     * @param values an array of shorts containing the values in
     * order of increasing code length.
     * @throws IllegalArgumentException if {@code lengths} or
     * {@code values} are null, the length of {@code lengths} is
     * greater than 16, the length of {@code values} is greater than 256,
     * if any value in {@code lengths} or {@code values} is less
     * than zero, or if the arrays do not describe a valid Huffman table.
     */
    public JPEGHuffmanTable(short[] lengths, short[] values) {
        if (lengths == null || values == null ||
            lengths.length == 0 || values.length == 0 ||
            lengths.length > 16 || values.length > 256) {
            throw new IllegalArgumentException("Illegal lengths or values");
        }
        for (int i = 0; i<lengths.length; i++) {
            if (lengths[i] < 0) {
                throw new IllegalArgumentException("lengths["+i+"] < 0");
            }
        }
        for (int i = 0; i<values.length; i++) {
            if (values[i] < 0) {
                throw new IllegalArgumentException("values["+i+"] < 0");
            }
        }
        this.lengths = Arrays.copyOf(lengths, lengths.length);
        this.values = Arrays.copyOf(values, values.length);
        validate();
    }

    private void validate() {
        int sumOfLengths = 0;
        for (int i=0; i<lengths.length; i++) {
            sumOfLengths += lengths[i];
        }
        if (sumOfLengths != values.length) {
            throw new IllegalArgumentException("lengths do not correspond " +
                                               "to length of value table");
        }
    }

    /* Internal version which avoids the overhead of copying and checking */
    private JPEGHuffmanTable(short[] lengths, short[] values, boolean copy) {
        if (copy) {
            this.lengths = Arrays.copyOf(lengths, lengths.length);
            this.values = Arrays.copyOf(values, values.length);
        } else {
            this.lengths = lengths;
            this.values = values;
        }
    }

    
Returns an array of shorts containing the number of values for each length in the Huffman table. The returned array is a copy. 
See Also:
Returns:a short array where array[k-1] is equal to the number of values in the table of length k.
/**
     * Returns an array of {@code short}s containing the number of values
     * for each length in the Huffman table. The returned array is a copy.
     *
     * @return a {@code short} array where {@code array[k-1]}
     * is equal to the number of values in the table of length {@code k}.
     * @see #getValues
     */
    public short[] getLengths() {
        return Arrays.copyOf(lengths, lengths.length);
    }

    
Returns an array of shorts containing the values arranged by increasing length of their corresponding codes. The interpretation of the array is dependent on the values returned from getLengths. The returned array is a copy. 
See Also:
Returns:a short array of values.
/**
     * Returns an array of {@code short}s containing the values arranged
     * by increasing length of their corresponding codes.
     * The interpretation of the array is dependent on the values returned
     * from {@code getLengths}. The returned array is a copy.
     *
     * @return a {@code short} array of values.
     * @see #getLengths
     */
    public short[] getValues() {
        return Arrays.copyOf(values, values.length);
    }

    
Returns a String representing this Huffman table. 
Returns:a String representing this Huffman table.
/**
     * Returns a {@code String} representing this Huffman table.
     * @return a {@code String} representing this Huffman table.
     */
    public String toString() {
        String ls = System.getProperty("line.separator", "\n");
        StringBuilder sb = new StringBuilder("JPEGHuffmanTable");
        sb.append(ls).append("lengths:");
        for (int i=0; i<lengths.length; i++) {
            sb.append(" ").append(lengths[i]);
        }
        sb.append(ls).append("values:");
        for (int i=0; i<values.length; i++) {
            sb.append(" ").append(values[i]);
        }
        return sb.toString();
    }
}