PngChunkZtxt.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.IOException;

import org.apache.commons.imaging.ImageReadException;
import org.apache.commons.imaging.common.ZLibUtils;
import org.apache.commons.imaging.formats.png.PngConstants;
import org.apache.commons.imaging.formats.png.PngText;

public class PngChunkZtxt extends PngTextChunk {

    public final String keyword, text;

    public PngChunkZtxt(final int length, final int chunkType, final int crc, final byte bytes[])
            throws ImageReadException, IOException {
        super(length, chunkType, crc, bytes);

        int index = findNull(bytes);
        if (index < 0) {
            throw new ImageReadException(
                    "PNG zTXt chunk keyword is unterminated.");
        }

        keyword = new String(bytes, 0, index, "ISO-8859-1");
        index++;

        final int compressionMethod = bytes[index++];
        if (compressionMethod != PngConstants.COMPRESSION_DEFLATE_INFLATE) {
            throw new ImageReadException(
                    "PNG zTXt chunk has unexpected compression method: "
                            + compressionMethod);
        }

        final int compressedTextLength = bytes.length - index;
        final byte compressedText[] = new byte[compressedTextLength];
        System.arraycopy(bytes, index, compressedText, 0,
                compressedTextLength);

        text = new String(new ZLibUtils().inflate(compressedText),
                "ISO-8859-1");
    }

    /**
     * @return Returns the keyword.
     */
    @Override
    public String getKeyword() {
        return keyword;
    }

    /**
     * @return Returns the text.
     */
    @Override
    public String getText() {
        return text;
    }

    @Override
    public PngText getContents() {
        return new PngText.Ztxt(keyword, text);
    }

}