PngChunkItxt.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 PngChunkItxt extends PngTextChunk {
    public final String keyword, text;

    /*
     * The language tag defined in [RFC-3066] indicates the human language used
     * by the translated keyword and the text. Unlike the keyword, the language
     * tag is case-insensitive. It is an ISO 646.IRV:1991 [ISO 646] string
     * consisting of hyphen-separated words of 1-8 alphanumeric characters each
     * (for example cn, en-uk, no-bok, x-klingon, x-KlInGoN). If the first word
     * is two or three letters long, it is an ISO language code [ISO-639]. If
     * the language tag is empty, the language is unspecified.
     */
    public final String languageTag;

    public final String translatedKeyword;

    public PngChunkItxt(final int length, final int chunkType, final int crc, final byte bytes[])
            throws ImageReadException, IOException {
        super(length, chunkType, crc, bytes);
        int terminator = findNull(bytes);
        if (terminator < 0) {
            throw new ImageReadException(
                    "PNG iTXt chunk keyword is not terminated.");
        }

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

        final int compressionFlag = bytes[index++];
        if (compressionFlag != 0 && compressionFlag != 1) {
            throw new ImageReadException(
                    "PNG iTXt chunk has invalid compression flag: "
                            + compressionFlag);
        }

        final boolean compressed = compressionFlag == 1;

        final int compressionMethod = bytes[index++];
        if (compressed) {
            if (compressionMethod != PngConstants.COMPRESSION_DEFLATE_INFLATE) {
                throw new ImageReadException(
                        "PNG iTXt chunk has unexpected compression method: "
                                + compressionMethod);
            } else if (compressionMethod != 0) {
                throw new ImageReadException(
                        "PNG iTXt chunk has unexpected compression method: "
                                + compressionMethod);
            }
        }

        terminator = findNull(bytes, index);
        if (terminator < 0) {
            throw new ImageReadException(
                    "PNG iTXt chunk language tag is not terminated.");
        }

        languageTag = new String(bytes, index, terminator - index,
                "ISO-8859-1");
        index = terminator + 1;

        terminator = findNull(bytes, index);
        if (terminator < 0) {
            throw new ImageReadException(
                    "PNG iTXt chunk translated keyword is not terminated.");
        }

        translatedKeyword = new String(bytes, index, terminator - index,
                "utf-8");
        index = terminator + 1;

        if (compressed) {
            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),
                    "utf-8");

        } else {
            text = new String(bytes, index, bytes.length - index, "utf-8");
        }
    }

    /**
     * @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.Itxt(keyword, text, languageTag, translatedKeyword);
    }
}