src/main/java/org/apache/pdfbox/jbig2/JBIG2ImageReaderSpi.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.pdfbox.jbig2;

import java.io.IOException;
import java.util.Locale;

import javax.imageio.ImageReader;
import javax.imageio.spi.ImageReaderSpi;
import javax.imageio.stream.ImageInputStream;

/**
 * Necessary extension for ImageIO standard.
 * 
 * @see ImageReaderSpi
 */
public class JBIG2ImageReaderSpi extends ImageReaderSpi
{

    private static final String VENDOR = "Apache Software Foundation";
    private static final String VERSION = "1.4.1";
    private static final String READER_CLASS_NAME = "org.apache.pdfbox.jbig2.JBIG2ImageReader";
    private static final String[] NAMES = { "jbig2", "JBIG2" };
    private static final String[] SUFFIXES = { "jb2", "jbig2", "JB2", "JBIG2" };
    private static final String[] MIME_TYPES = { "image/x-jbig2", "image/x-jb2" };
    private static final Class<?>[] INPUT_TYPES = { ImageInputStream.class };

    /**
     * According to D.4.1:
     * <p>
     * This preamble contains the unique id string for jbig2 files and can be used to check if this reader plugin can
     * decode the given stream. This can only work with native jbig2 data. If the stream is embedded in another file
     * format this preamble might be missing.
     */
    private static final int[] FILEHEADER_PREAMBLE = { 0x97, 0x4A, 0x42, 0x32, 0x0D, 0x0A, 0x1A,
            0x0A };

    /* MK: I suppose, there won't be a writer in near future :-) */
    private static final String[] WRITER_SPI_NAMES = {};

    static final boolean SUPPORTS_STANDARD_STREAM_METADATE_FORMAT = false;
    static final String NATIVE_STREAM_METADATA_FORMAT_NAME = "JBIG2 Stream Metadata";
    static final String NATIVE_STREAM_METADATA_FORMAT_CLASSNAME = "JBIG2Metadata";
    static final String[] EXTRA_STREAM_METADATA_FORMAT_NAME = null;
    static final String[] EXTRA_STREAM_METADATA_FORMAT_CLASSNAME = null;

    static final boolean SUPPORTS_STANDARD_IMAGE_METADATA_FORMAT = false;
    static final String NATIVE_IMAGE_METADATA_FORMAT_NAME = "JBIG2 File Metadata";
    static final String NATIVE_IMAGE_METADATA_FORMAT_CLASSNAME = "JBIG2Metadata";
    static final String[] EXTRA_IMAGE_METADATA_FORMAT_NAME = null;
    static final String[] EXTRA_IMAGE_METADATA_FORMAT_CLASSNAME = null;

    public JBIG2ImageReaderSpi()
    {
        super(VENDOR, VERSION, NAMES, SUFFIXES, MIME_TYPES, READER_CLASS_NAME, INPUT_TYPES,
                WRITER_SPI_NAMES, SUPPORTS_STANDARD_STREAM_METADATE_FORMAT,
                NATIVE_STREAM_METADATA_FORMAT_NAME, NATIVE_STREAM_METADATA_FORMAT_CLASSNAME,
                EXTRA_STREAM_METADATA_FORMAT_NAME, EXTRA_STREAM_METADATA_FORMAT_CLASSNAME,
                SUPPORTS_STANDARD_IMAGE_METADATA_FORMAT, NATIVE_IMAGE_METADATA_FORMAT_NAME,
                NATIVE_IMAGE_METADATA_FORMAT_CLASSNAME, EXTRA_IMAGE_METADATA_FORMAT_NAME,
                EXTRA_IMAGE_METADATA_FORMAT_CLASSNAME);
    }

    /*
     * Checks, if the file header begins with the preamble id string defined in D.4.1, page 100
     * 
     * (non-Javadoc)
     * 
     * @see javax.imageio.spi.ImageReaderSpi#canDecodeInput(java.lang.Object)
     */
    @Override
    public boolean canDecodeInput(Object source) throws IOException
    {
        if (source == null)
            throw new IllegalArgumentException("source must not be null");

        if (!(source instanceof ImageInputStream))
        {
            System.out.println("source is not an ImageInputStream");
            return false;
        }

        ImageInputStream iis = (ImageInputStream) source;
        iis.mark();

        for (int i = 0; i < FILEHEADER_PREAMBLE.length; i++)
        {
            int read = (iis.read() & 0xFF);
            if (read != FILEHEADER_PREAMBLE[i])
            {
                return false;
            }
        }

        iis.reset();
        return true;
    }

    @Override
    public ImageReader createReaderInstance(Object extension) throws IOException
    {
        return new JBIG2ImageReader(this);
    }

    @Override
    public String getDescription(Locale locale)
    {
        return "JBIG2 Image Reader";
    }

}