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/* Copyright (c) 2014, David A. Clunie DBA Pixelmed Publishing. All rights reserved. */
package com.pixelmed.codec.jpeg;
/**
* <p>A JPEG Huffman Table.</p>
*
* @author dclunie
*/
public class HuffmanTable {
private static final String identString = "@(#) $Header: /userland/cvs/codec/com/pixelmed/codec/jpeg/HuffmanTable.java,v 1.4 2014/03/23 11:41:54 dclunie Exp $";
private int TableClass;
private int HuffmanTableIdentifier;
private int[] nHuffmanCodesOfLengthI;
private int[][] ValueOfHuffmanCodeIJ;
public HuffmanTable(int TableClass,int HuffmanTableIdentifier,int[] nHuffmanCodesOfLengthI,int[][] ValueOfHuffmanCodeIJ) {
this.TableClass = TableClass;
this.HuffmanTableIdentifier = HuffmanTableIdentifier;
this.nHuffmanCodesOfLengthI = nHuffmanCodesOfLengthI;
this.ValueOfHuffmanCodeIJ = ValueOfHuffmanCodeIJ;
expand();
}
private int countNumberOfCodes() {
int count=0;
for (int i=0; i<nHuffmanCodesOfLengthI.length; ++i) {
count += nHuffmanCodesOfLengthI[i];
}
return count;
}
// a literal implementation of 10918-1 F.2.2.3 and figure F.15
private int[] BITS = new int[17]; // number of codes of each size for code size I 1-16 (index 0 unused)
private int[] HUFFVAL; // array of values in same order as encoded in ValueOfHuffmanCodeIJ with dimension nCodes + 1 to account for unused 0 index
private int[] HUFFSIZE;
private int[] HUFFCODE;
private int[] MINCODE = new int[17]; // the smallest code value for code size I 1-16 (index 0 unused)
private int[] MAXCODE = new int[17]; // the largest code value for code size I 1-16 (index 0 unused)
private int[] VALPTR = new int[17]; // index to the start of the list of values in HUFFVAL (indexed from 1 not 0)
public int[] getMINCODE() { return MINCODE; };
public int[] getMAXCODE() { return MAXCODE; };
public int[] getVALPTR() { return VALPTR; };
public int[] getHUFFVAL() { return HUFFVAL; };
// for our redaction purposes, we need to replace AC coefficients with all zeroes (EOB), so take note of this code whilst expanding tables
private int EOBCode;
private int EOBCodeLength;
public int getEOBCode() { return EOBCode; }
public int getEOBCodeLength() { return EOBCodeLength; }
private void expand() {
//System.err.println("HuffmanTable.expand(): class="+TableClass+" identifier="+HuffmanTableIdentifier);
// list BITS(1..16) number of codes of each size ... is nHuffmanCodesOfLengthI(0..15)
for (int I=1; I<=16; ++I) {
//System.err.println("HuffmanTable.expand(): I="+I);
BITS[I] = nHuffmanCodesOfLengthI[I-1];
}
int nCodes = countNumberOfCodes();
// HUFFVAL is a flat list of codes in the order read they are encoded in the DHT segment, which is already sorted into ascending orded
{
HUFFVAL = new int[nCodes+1];
int J = 0; // N.B. This is one of the few tables in ISO 10918-1 that starts with an index of zero, not one; must match VALPTR values used as indices into HUFFVAL
for (int i=0; i<nHuffmanCodesOfLengthI.length; ++i) {
int nCodesThisLength = nHuffmanCodesOfLengthI[i];
if (nCodesThisLength > 0) {
for (int j=0; j<nCodesThisLength; ++j) {
HUFFVAL[J] = ValueOfHuffmanCodeIJ[i][j];
++J;
}
}
}
}
// 10918-1 C.2 Figure C.1 Generate_size_table
// HUFFSIZE contains a list of code lengths
//int LASTK = 0;
HUFFSIZE = new int[nCodes+1];
{
int K=0;
int I=1;
int J=1;
while (true) {
if (J > BITS[I]) {
++I;
J=1;
if (I > 16) {
HUFFSIZE[K] = 0;
//LASTK = K;
break;
}
}
else {
HUFFSIZE[K] = I;
++K;
++J;
}
}
}
// 10918-1 C.2 Figure C.2 Generate_code_table
// HUFFCODE contains a code for each size in HUFFSIZE
HUFFCODE = new int[nCodes+1];
{
int K=0;
int CODE=0;
int SI = HUFFSIZE[0];
while (true) {
HUFFCODE[K] = CODE;
++CODE;
++K;
if (SI != HUFFSIZE[K]) {
if (HUFFSIZE[K] == 0) break;
do {
CODE = CODE << 1;
++SI;
} while (SI != HUFFSIZE[K]);
}
}
}
// 10918-1 C.2 Figure F.15 Decoder_tables generation
{
int I=0;
int J=0;
while (true) {
++I;
if (I > 16) break;
if (BITS[I] == 0) {
MAXCODE[I] = -1;
}
else {
VALPTR[I] = J;
MINCODE[I] = HUFFCODE[J];
J = J + BITS[I] - 1;
MAXCODE[I] = HUFFCODE[J];
++J;
}
}
}
// walk the arrays to find the EOB code and its length
{
for (int I=1; I<=16; ++I) {
for (int J = VALPTR[I]; J < VALPTR[I] + BITS[I]; ++J) {
if (HUFFVAL[J] == 0) { // 0x00 is the EOB code (rrrrssss == 0)
EOBCode = HUFFCODE[J];
EOBCodeLength = I;
}
}
}
}
}
public String toString() {
StringBuffer buf = new StringBuffer();
buf.append("Huffman Table:\n");
buf.append("\t TableClass = " +TableClass+"\n");
buf.append("\t HuffmanTableIdentifier = "+HuffmanTableIdentifier+"\n");
for (int i=0; i<16; ++i) {
buf.append("\t\t nHuffmanCodesOfLength "+i+" = "+nHuffmanCodesOfLengthI[i]+"\n");
for (int j=0; j<nHuffmanCodesOfLengthI[i];++j) {
buf.append("\t\t\t ValueOfHuffmanCode "+j+" = "+ValueOfHuffmanCodeIJ[i][j]+"\n");
}
}
buf.append("\t Expanded:\n");
for (int I=1; I<=16; ++I) {
buf.append("\t\t["+I+"] MINCODE="+Integer.toBinaryString(MINCODE[I])+" MAXCODE="+Integer.toBinaryString(MAXCODE[I])+""+" VALPTR="+VALPTR[I]+"\n");
}
for (int J=0; J<HUFFVAL.length; ++J) {
buf.append("\t\t["+J+"] HUFFVAL=0x"+Integer.toHexString(HUFFVAL[J])+"\n");
}
buf.append("\t\tEOBCode="+Integer.toBinaryString(EOBCode)+" 0x"+Integer.toHexString(EOBCode)+" (length "+EOBCodeLength+" dec)\n");
return buf.toString();
}
}
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