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/*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
* under the License.
*/
package org.apache.commons.imaging.formats.jpeg.segments;
import java.io.ByteArrayInputStream;
import java.io.IOException;
import java.io.InputStream;
import java.util.ArrayList;
import java.util.Collections;
import java.util.List;
import static org.apache.commons.imaging.common.BinaryFunctions.*;
public class DhtSegment extends Segment {
public final List huffmanTables;
public static class HuffmanTable {
// some arrays are better off one-based
// to avoid subtractions by one later when indexing them
public final int tableClass;
public final int destinationIdentifier;
private final int[] bits; // 1-based
private final int[] huffVal; // 0-based
// derived properties:
private final int[] huffSize = new int[16 * 256]; // 0-based
private final int[] huffCode; // 0-based
private final int[] minCode = new int[1 + 16]; // 1-based
private final int[] maxCode = new int[1 + 16]; // 1-based
private final int[] valPtr = new int[1 + 16]; // 1-based
public HuffmanTable(final int tableClass, final int destinationIdentifier,
final int[] bits, final int[] huffVal) {
this.tableClass = tableClass;
this.destinationIdentifier = destinationIdentifier;
this.bits = bits;
this.huffVal = huffVal;
// "generate_size_table", section C.2, figure C.1, page 51 of ITU-T
// T.81:
int k = 0;
int i = 1;
int j = 1;
int lastK = -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++;
}
}
// "generate_code_table", section C.2, figure C.2, page 52 of ITU-T
// T.81:
k = 0;
int code = 0;
int si = huffSize[0];
huffCode = new int[lastK];
while (true) {
huffCode[k] = code;
code++;
k++;
if (huffSize[k] == si) {
continue;
}
if (huffSize[k] == 0) {
break;
}
do {
code <<= 1;
si++;
} while (huffSize[k] != si);
}
// "Decoder_tables", section F.2.2.3, figure F.15, page 108 of T.81:
i = 0;
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 += bits[i] - 1;
maxCode[i] = huffCode[j];
j++;
}
}
}
public int[] getBits() {
return bits;
}
public int[] getHuffVal() {
return huffVal;
}
public int[] getHuffSize() {
return huffSize;
}
public int[] getHuffCode() {
return huffCode;
}
public int[] getMinCode() {
return minCode;
}
public int[] getMaxCode() {
return maxCode;
}
public int[] getValPtr() {
return valPtr;
}
}
public DhtSegment(final int marker, final byte[] segmentData) throws IOException {
this(marker, segmentData.length, new ByteArrayInputStream(segmentData));
}
public DhtSegment(final int marker, int length, final InputStream is)
throws IOException {
super(marker, length);
final ArrayList huffmanTables = new ArrayList();
while (length > 0) {
final int tableClassAndDestinationId = 0xff & readByte(
"TableClassAndDestinationId", is, "Not a Valid JPEG File");
length--;
final int tableClass = (tableClassAndDestinationId >> 4) & 0xf;
final int destinationIdentifier = tableClassAndDestinationId & 0xf;
final int[] bits = new int[1 + 16];
int bitsSum = 0;
for (int i = 1; i < bits.length; i++) {
bits[i] = 0xff & readByte("Li", is, "Not a Valid JPEG File");
length--;
bitsSum += bits[i];
}
final int[] huffVal = new int[bitsSum];
for (int i = 0; i < bitsSum; i++) {
huffVal[i] = 0xff & readByte("Vij", is, "Not a Valid JPEG File");
length--;
}
huffmanTables.add(new HuffmanTable(tableClass,
destinationIdentifier, bits, huffVal));
}
this.huffmanTables = Collections.unmodifiableList(huffmanTables);
}
@Override
public String getDescription() {
return "DHT (" + getSegmentType() + ")";
}
}
