PngChunk.java
/*
* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership.
* The ASF licenses this file to You 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.
*/
package org.apache.commons.imaging.formats.png.chunks;
import java.io.ByteArrayInputStream;
import java.util.Objects;
import org.apache.commons.imaging.common.BinaryFileParser;
/**
* A PNG image is composed of several chunks. This is the base class for the chunks, used by the parser.
*
* @see <a href="https://en.wikipedia.org/wiki/Portable_Network_Graphics#%22Chunks%22_within_the_file">Portable_Network_Graphics</a>
*/
public class PngChunk extends BinaryFileParser {
private final int length;
private final int chunkType;
private final int crc;
private final byte[] bytes;
private final boolean[] propertyBits;
private final boolean ancillary;
private final boolean isPrivate;
private final boolean reserved;
private final boolean safeToCopy;
/**
* Constructs a new instance.
*
* @param length chunk length
* @param chunkType chunk type
* @param crc CRC computed over the chunk type and chunk data (but not the length)
* @param bytes chunk data bytes
* @throws NullPointerException if bytes is null.
*/
public PngChunk(final int length, final int chunkType, final int crc, final byte[] bytes) {
this.length = length;
this.chunkType = chunkType;
this.crc = crc;
this.bytes = Objects.requireNonNull(bytes, "bytes").clone();
propertyBits = new boolean[4];
int shift = 24;
final int theMask = 1 << 5;
for (int i = 0; i < propertyBits.length; i++) {
final int theByte = 0xff & chunkType >> shift;
shift -= 8;
propertyBits[i] = (theByte & theMask) > 0;
}
ancillary = propertyBits[0];
isPrivate = propertyBits[1];
reserved = propertyBits[2];
safeToCopy = propertyBits[3];
}
/**
* Gets a copy of the chunk bytes.
*
* @return the chunk bytes
*/
public byte[] getBytes() {
return bytes.clone();
}
public int getChunkType() {
return chunkType;
}
public int getCrc() {
return crc;
}
/**
* Gets a new {@link ByteArrayInputStream} for the chunk bytes.
*
* <p>
* The caller is responsible for closing the resource.
* </p>
*
* @return a ByteArrayInputStream for the chunk bytes
*/
protected ByteArrayInputStream getDataStream() {
return new ByteArrayInputStream(bytes);
}
public int getLength() {
return length;
}
/**
* Gets a copy of the chunk property bits.
*
* @return the chunk property bits
*/
public boolean[] getPropertyBits() {
return propertyBits.clone();
}
public boolean isAncillary() {
return ancillary;
}
public boolean isPrivate() {
return isPrivate;
}
public boolean isReserved() {
return reserved;
}
public boolean isSafeToCopy() {
return safeToCopy;
}
}