/*
 * ImageInfo.java
 *
 * Version 1.9
 *
 * A Java class to determine image width, height and color depth for
 * a number of image file formats.
 *
 * Written by Marco Schmidt 
 *
 * Contributed to the Public Domain.
 */

package org.modeshape.sequencer.image;

import java.io.DataInput;
import java.io.FileInputStream;
import java.io.IOException;
import java.io.InputStream;
import java.net.URL;
import java.util.Vector;

/**
 * Get file format, image resolution, number of bits per pixel and optionally number of images, comments and physical resolution
 * from JPEG, GIF, BMP, PCX, PNG, IFF, RAS, PBM, PGM, PPM and PSD files (or input streams).
 * <p>
 * Use the class like this:
 * 
 * <pre>
 * ImageMetadata ii = new ImageMetadata();
 * ii.setInput(in); // in can be InputStream or RandomAccessFile
 * ii.setDetermineImageNumber(true); // default is false
 * ii.setCollectComments(true); // default is false
 * if (!ii.check()) {
 *     System.err.println(&quot;Not a supported image file format.&quot;);
 *     return;
 * }
 * System.out.println(ii.getFormatName() + &quot;, &quot; + ii.getMimeType() + &quot;, &quot; + ii.getWidth() + &quot; x &quot; + ii.getHeight() + &quot; pixels, &quot;
 *                    + ii.getBitsPerPixel() + &quot; bits per pixel, &quot; + ii.getNumberOfImages() + &quot; image(s), &quot;
 *                    + ii.getNumberOfComments() + &quot; comment(s).&quot;);
 * // there are other properties, check out the API documentation
 * </pre>
 * 
 * You can also use this class as a command line program. Call it with a number of image file names and URLs as parameters:
 * 
 * <pre>
 *   java ImageMetadata *.jpg *.png *.gif http://somesite.tld/image.jpg
 * </pre>
 * 
 * or call it without parameters and pipe data to it:
 * 
 * <pre>
 *   java ImageMetadata &lt; image.jpg  
 * </pre>
 * 
 * <p>
 * Known limitations:
 * <ul>
 * <li>When the determination of the number of images is turned off, GIF bits per pixel are only read from the global header. For
 * some GIFs, local palettes change this to a typically larger value. To be certain to get the correct color depth, call
 * setDetermineImageNumber(true) before calling check(). The complete scan over the GIF file will take additional time.</li>
 * <li>Transparency information is not included in the bits per pixel count. Actually, it was my decision not to include those
 * bits, so it's a feature! ;-)</li>
 * </ul>
 * <p>
 * Requirements:
 * <ul>
 * <li>Java 1.1 or higher</li>
 * </ul>
 * <p>
 * The latest version can be found at <a href="http://schmidt.devlib.org/image-info/">http://schmidt.devlib.org/image-info/</a>.
 * <p>
 * Written by Marco Schmidt.
 * <p>
 * This class is contributed to the Public Domain. Use it at your own risk.
 * <p>
 * <a name="history">History</a>:
 * <ul>
 * <li><strong>2001-08-24</strong> Initial version.</li>
 * <li><strong>2001-10-13</strong> Added support for the file formats BMP and PCX.</li>
 * <li><strong>2001-10-16</strong> Fixed bug in read(int[], int, int) that returned
 * <li><strong>2002-01-22</strong> Added support for file formats Amiga IFF and Sun Raster (RAS).</li>
 * <li><strong>2002-01-24</strong> Added support for file formats Portable Bitmap / Graymap / Pixmap (PBM, PGM, PPM) and Adobe
 * Photoshop (PSD). Added new method getMimeType() to return the MIME type associated with a particular file format.</li>
 * <li><strong>2002-03-15</strong> Added support to recognize number of images in file. Only works with GIF. Use
 * {@link #setDetermineImageNumber} with <code>true</code> as argument to identify animated GIFs ({@link #getNumberOfImages()}
 * will return a value larger than <code>1</code>).</li>
 * <li><strong>2002-04-10</strong> Fixed a bug in the feature 'determine number of images in animated GIF' introduced with
 * version 1.1. Thanks to Marcelo P. Lima for sending in the bug report. Released as 1.1.1.</li>
 * <li><strong>2002-04-18</strong> Added {@link #setCollectComments(boolean)}. That new method lets the user specify whether
 * textual comments are to be stored in an internal list when encountered in an input image file / stream. Added two methods to
 * return the physical width and height of the image in dpi: {@link #getPhysicalWidthDpi()} and {@link #getPhysicalHeightDpi()}.
 * If the physical resolution could not be retrieved, these methods return <code>-1</code>. </li>
 * <li><strong>2002-04-23</strong> Added support for the new properties physical resolution and comments for some formats.
 * Released as 1.2.</li>
 * <li><strong>2002-06-17</strong> Added support for SWF, sent in by Michael Aird. Changed checkJpeg() so that other APP markers
 * than APP0 will not lead to a failure anymore. Released as 1.3.</li>
 * <li><strong>2003-07-28</strong> Bug fix - skip method now takes return values into consideration. Less bytes than necessary
 * may have been skipped, leading to flaws in the retrieved information in some cases. Thanks to Bernard Bernstein for pointing
 * that out. Released as 1.4.</li>
 * <li><strong>2004-02-29</strong> Added support for recognizing progressive JPEG and interlaced PNG and GIF. A new method
 * {@link #isProgressive()} returns whether ImageMetadata has found that the storage type is progressive (or interlaced). Thanks
 * to Joe Germuska for suggesting the feature. Bug fix: BMP physical resolution is now correctly determined. Released as 1.5.</li>
 * <li><strong>2004-11-30</strong> Bug fix: recognizing progressive GIFs (interlaced in GIF terminology) did not work (thanks to
 * Franz Jeitler for pointing this out). Now it should work, but only if the number of images is determined. This is because
 * information on interlacing is stored in a local image header. In theory, different images could be stored interlaced and
 * non-interlaced in one file. However, I think that's unlikely. Right now, the last image in the GIF file that is examined by
 * ImageMetadata is used for the "progressive" status.</li>
 * <li><strong>2005-01-02</strong> Some code clean up (unused methods and variables commented out, missing javadoc comments,
 * etc.). Thanks to George Sexton for a long list. Removed usage of Boolean.toString because it's a Java 1.4+ feature (thanks to
 * Gregor Dupont). Changed delimiter character in compact output from semicolon to tabulator (for better integration with cut(1)
 * and other Unix tools). Added some points to the <a href="http://schmidt.devlib.org/image-info/index.html#knownissues">'Known
 * issues' section of the website</a>. Released as 1.6.</li>
 * <li><strong>2005-07-26</strong> Removed code to identify Flash (SWF) files. Has repeatedly led to problems and support
 * requests, and I don't know the format and don't have the time and interest to fix it myself. I repeatedly included fixes by
 * others which didn't work for some people. I give up on SWF. Please do not contact me about it anymore. Set package of
 * ImageMetadata class to org.devlib.schmidt.imageinfo (a package was repeatedly requested by some users). Released as 1.7.</li>
 * <li><strong>2006-02-23</strong> Removed Flash helper methods which weren't used elsewhere. Updated skip method which tries
 * "read" whenever "skip(Bytes)" returns a result of 0. The old method didn't work with certain input stream types on truncated
 * data streams. Thanks to Martin Leidig for reporting this and sending in code. Released as 1.8.</li>
 * </li>
 * <li><strong>2006-11-13</strong> Removed check that made ImageMetadata report JPEG APPx markers smaller than 14 bytes as files
 * in unknown format. Such JPEGs seem to be generated by Google's Picasa application. First reported with fix by Karl von Randow.
 * Released as 1.9.</li>
 * <li><strong>2008-04-10</strong> Changed comment vector to be <code>Vector&lt;String&gt;</code>, and removed any
 * unnecessary casting. Also removed the unnecessary else statements where the previous block ended in a return. Also renamed to
 * <code>ImageMetadata</code>.
 * </ul>
 * 
 * @author Marco Schmidt
 */
public class ImageMetadata {

    /**
     * Return value of {@link #getFormat()} for JPEG streams. ImageMetadata can extract physical resolution and comments from
     * JPEGs (only from APP0 headers). Only one image can be stored in a file. It is determined whether the JPEG stream is
     * progressive (see {@link #isProgressive()}).
     */
    public static final int FORMAT_JPEG = 0;

    /**
     * Return value of {@link #getFormat()} for GIF streams. ImageMetadata can extract comments from GIFs and count the number of
     * images (GIFs with more than one image are animations). It is determined whether the GIF stream is interlaced (see
     * {@link #isProgressive()}).
     */
    public static final int FORMAT_GIF = 1;

    /**
     * Return value of {@link #getFormat()} for PNG streams. PNG only supports one image per file. Both physical resolution and
     * comments can be stored with PNG, but ImageMetadata is currently not able to extract those. It is determined whether the PNG
     * stream is interlaced (see {@link #isProgressive()}).
     */
    public static final int FORMAT_PNG = 2;

    /**
     * Return value of {@link #getFormat()} for BMP streams. BMP only supports one image per file. BMP does not allow for
     * comments. The physical resolution can be stored.
     */
    public static final int FORMAT_BMP = 3;

    /**
     * Return value of {@link #getFormat()} for PCX streams. PCX does not allow for comments or more than one image per file.
     * However, the physical resolution can be stored.
     */
    public static final int FORMAT_PCX = 4;

    /**
     * Return value of {@link #getFormat()} for IFF streams.
     */
    public static final int FORMAT_IFF = 5;

    /**
     * Return value of {@link #getFormat()} for RAS streams. Sun Raster allows for one image per file only and is not able to
     * store physical resolution or comments.
     */
    public static final int FORMAT_RAS = 6;

    /** Return value of {@link #getFormat()} for PBM streams. */
    public static final int FORMAT_PBM = 7;

    /** Return value of {@link #getFormat()} for PGM streams. */
    public static final int FORMAT_PGM = 8;

    /** Return value of {@link #getFormat()} for PPM streams. */
    public static final int FORMAT_PPM = 9;

    /** Return value of {@link #getFormat()} for PSD streams. */
    public static final int FORMAT_PSD = 10;

    /*
     * public static final int COLOR_TYPE_UNKNOWN = -1; public static final int COLOR_TYPE_TRUECOLOR_RGB = 0; public static final
     * int COLOR_TYPE_PALETTED = 1; public static final int COLOR_TYPE_GRAYSCALE= 2; public static final int
     * COLOR_TYPE_BLACK_AND_WHITE = 3;
     */

    /**
     * The names of all supported file formats. The FORMAT_xyz int constants can be used as index values for this array.
     */
    private static final String[] FORMAT_NAMES = {"JPEG", "GIF", "PNG", "BMP", "PCX", "IFF", "RAS", "PBM", "PGM", "PPM", "PSD"};

    /**
     * The names of the MIME types for all supported file formats. The FORMAT_xyz int constants can be used as index values for
     * this array.
     */
    private static final String[] MIME_TYPE_STRINGS = {"image/jpeg", "image/gif", "image/png", "image/bmp", "image/pcx",
        "image/iff", "image/ras", "image/x-portable-bitmap", "image/x-portable-graymap", "image/x-portable-pixmap", "image/psd"};

    private int width;
    private int height;
    private int bitsPerPixel;
    // private int colorType = COLOR_TYPE_UNKNOWN;
    private boolean progressive;
    private int format;
    private InputStream in;
    private DataInput din;
    private boolean collectComments = true;
    private Vector<String> comments;
    private boolean determineNumberOfImages;
    private int numberOfImages;
    private int physicalHeightDpi;
    private int physicalWidthDpi;

    private void addComment( String s ) {
        if (comments == null) {
            comments = new Vector<String>();
        }
        comments.addElement(s);
    }

    /**
     * Call this method after you have provided an input stream or file using {@link #setInput(InputStream)} or
     * {@link #setInput(DataInput)}. If true is returned, the file format was known and information on the file's content can be
     * retrieved using the various getXyz methods.
     * 
     * @return if information could be retrieved from input
     */
    public boolean check() {
        format = -1;
        width = -1;
        height = -1;
        bitsPerPixel = -1;
        numberOfImages = 1;
        physicalHeightDpi = -1;
        physicalWidthDpi = -1;
        comments = null;
        try {
            int b1 = read() & 0xff;
            int b2 = read() & 0xff;
            if (b1 == 0x47 && b2 == 0x49) {
                return checkGif();
            } else if (b1 == 0x89 && b2 == 0x50) {
                return checkPng();
            } else if (b1 == 0xff && b2 == 0xd8) {
                return checkJpeg();
            } else if (b1 == 0x42 && b2 == 0x4d) {
                return checkBmp();
            } else if (b1 == 0x0a && b2 < 0x06) {
                return checkPcx();
            } else if (b1 == 0x46 && b2 == 0x4f) {
                return checkIff();
            } else if (b1 == 0x59 && b2 == 0xa6) {
                return checkRas();
            } else if (b1 == 0x50 && b2 >= 0x31 && b2 <= 0x36) {
                return checkPnm(b2 - '0');
            } else if (b1 == 0x38 && b2 == 0x42) {
                return checkPsd();
            } else {
                return false;
            }
        } catch (IOException ioe) {
            return false;
        }
    }

    private boolean checkBmp() throws IOException {
        byte[] a = new byte[44];
        if (read(a) != a.length) {
            return false;
        }
        width = getIntLittleEndian(a, 16);
        height = getIntLittleEndian(a, 20);
        if (width < 1 || height < 1) {
            return false;
        }
        bitsPerPixel = getShortLittleEndian(a, 26);
        if (bitsPerPixel != 1 && bitsPerPixel != 4 && bitsPerPixel != 8 && bitsPerPixel != 16 && bitsPerPixel != 24
            && bitsPerPixel != 32) {
            return false;
        }
        int x = (int)(getIntLittleEndian(a, 36) * 0.0254);
        if (x > 0) {
            setPhysicalWidthDpi(x);
        }
        int y = (int)(getIntLittleEndian(a, 40) * 0.0254);
        if (y > 0) {
            setPhysicalHeightDpi(y);
        }
        format = FORMAT_BMP;
        return true;
    }

    private boolean checkGif() throws IOException {
        final byte[] GIF_MAGIC_87A = {0x46, 0x38, 0x37, 0x61};
        final byte[] GIF_MAGIC_89A = {0x46, 0x38, 0x39, 0x61};
        byte[] a = new byte[11]; // 4 from the GIF signature + 7 from the global header
        if (read(a) != 11) {
            return false;
        }
        if ((!equals(a, 0, GIF_MAGIC_89A, 0, 4)) && (!equals(a, 0, GIF_MAGIC_87A, 0, 4))) {
            return false;
        }
        format = FORMAT_GIF;
        width = getShortLittleEndian(a, 4);
        height = getShortLittleEndian(a, 6);
        int flags = a[8] & 0xff;
        bitsPerPixel = ((flags >> 4) & 0x07) + 1;
        // progressive = (flags & 0x02) != 0;
        if (!determineNumberOfImages) {
            return true;
        }
        // skip global color palette
        if ((flags & 0x80) != 0) {
            int tableSize = (1 << ((flags & 7) + 1)) * 3;
            skip(tableSize);
        }
        numberOfImages = 0;
        int blockType;
        do {
            blockType = read();
            switch (blockType) {
                case (0x2c): // image separator
                {
                    if (read(a, 0, 9) != 9) {
                        return false;
                    }
                    flags = a[8] & 0xff;
                    progressive = (flags & 0x40) != 0;
                    /*
                     * int locWidth = getShortLittleEndian(a, 4); int locHeight = getShortLittleEndian(a, 6);
                     * System.out.println("LOCAL: " + locWidth + " x " + locHeight);
                     */
                    int localBitsPerPixel = (flags & 0x07) + 1;
                    if (localBitsPerPixel > bitsPerPixel) {
                        bitsPerPixel = localBitsPerPixel;
                    }
                    if ((flags & 0x80) != 0) {
                        skip((1 << localBitsPerPixel) * 3);
                    }
                    skip(1); // initial code length
                    int n;
                    do {
                        n = read();
                        if (n > 0) {
                            skip(n);
                        } else if (n == -1) {
                            return false;
                        }
                    } while (n > 0);
                    numberOfImages++;
                    break;
                }
                case (0x21): // extension
                {
                    int extensionType = read();
                    if (collectComments && extensionType == 0xfe) {
                        StringBuffer sb = new StringBuffer();
                        int n;
                        do {
                            n = read();
                            if (n == -1) {
                                return false;
                            }
                            if (n > 0) {
                                for (int i = 0; i < n; i++) {
                                    int ch = read();
                                    if (ch == -1) {
                                        return false;
                                    }
                                    sb.append((char)ch);
                                }
                            }
                        } while (n > 0);
                    } else {
                        int n;
                        do {
                            n = read();
                            if (n > 0) {
                                skip(n);
                            } else if (n == -1) {
                                return false;
                            }
                        } while (n > 0);
                    }
                    break;
                }
                case (0x3b): // end of file
                {
                    break;
                }
                default: {
                    return false;
                }
            }
        } while (blockType != 0x3b);
        return true;
    }

    private boolean checkIff() throws IOException {
        byte[] a = new byte[10];
        // read remaining 2 bytes of file id, 4 bytes file size
        // and 4 bytes IFF subformat
        if (read(a, 0, 10) != 10) {
            return false;
        }
        final byte[] IFF_RM = {0x52, 0x4d};
        if (!equals(a, 0, IFF_RM, 0, 2)) {
            return false;
        }
        int type = getIntBigEndian(a, 6);
        if (type != 0x494c424d && // type must be ILBM...
            type != 0x50424d20) { // ...or PBM
            return false;
        }
        // loop chunks to find BMHD chunk
        do {
            if (read(a, 0, 8) != 8) {
                return false;
            }
            int chunkId = getIntBigEndian(a, 0);
            int size = getIntBigEndian(a, 4);
            if ((size & 1) == 1) {
                size++;
            }
            if (chunkId == 0x424d4844) { // BMHD chunk
                if (read(a, 0, 9) != 9) {
                    return false;
                }
                format = FORMAT_IFF;
                width = getShortBigEndian(a, 0);
                height = getShortBigEndian(a, 2);
                bitsPerPixel = a[8] & 0xff;
                return (width > 0 && height > 0 && bitsPerPixel > 0 && bitsPerPixel < 33);
            }
            skip(size);
        } while (true);
    }

    private boolean checkJpeg() throws IOException {
        byte[] data = new byte[12];
        while (true) {
            if (read(data, 0, 4) != 4) {
                return false;
            }
            int marker = getShortBigEndian(data, 0);
            int size = getShortBigEndian(data, 2);
            if ((marker & 0xff00) != 0xff00) {
                return false; // not a valid marker
            }
            if (marker == 0xffe0) { // APPx
                if (size < 14) {
                    // not an APPx header as we know it, skip
                    skip(size - 2);
                    continue;
                }
                if (read(data, 0, 12) != 12) {
                    return false;
                }
                final byte[] APP0_ID = {0x4a, 0x46, 0x49, 0x46, 0x00};
                if (equals(APP0_ID, 0, data, 0, 5)) {
                    // System.out.println("data 7=" + data[7]);
                    if (data[7] == 1) {
                        setPhysicalWidthDpi(getShortBigEndian(data, 8));
                        setPhysicalHeightDpi(getShortBigEndian(data, 10));
                    } else if (data[7] == 2) {
                        int x = getShortBigEndian(data, 8);
                        int y = getShortBigEndian(data, 10);
                        setPhysicalWidthDpi((int)(x * 2.54f));
                        setPhysicalHeightDpi((int)(y * 2.54f));
                    }
                }
                skip(size - 14);
            } else if (collectComments && size > 2 && marker == 0xfffe) { // comment
                size -= 2;
                byte[] chars = new byte[size];
                if (read(chars, 0, size) != size) {
                    return false;
                }
                String comment = new String(chars, "iso-8859-1");
                comment = comment.trim();
                addComment(comment);
            } else if (marker >= 0xffc0 && marker <= 0xffcf && marker != 0xffc4 && marker != 0xffc8) {
                if (read(data, 0, 6) != 6) {
                    return false;
                }
                format = FORMAT_JPEG;
                bitsPerPixel = (data[0] & 0xff) * (data[5] & 0xff);
                progressive = marker == 0xffc2 || marker == 0xffc6 || marker == 0xffca || marker == 0xffce;
                width = getShortBigEndian(data, 3);
                height = getShortBigEndian(data, 1);
                return true;
            } else {
                skip(size - 2);
            }
        }
    }

    private boolean checkPcx() throws IOException {
        byte[] a = new byte[64];
        if (read(a) != a.length) {
            return false;
        }
        if (a[0] != 1) { // encoding, 1=RLE is only valid value
            return false;
        }
        // width / height
        int x1 = getShortLittleEndian(a, 2);
        int y1 = getShortLittleEndian(a, 4);
        int x2 = getShortLittleEndian(a, 6);
        int y2 = getShortLittleEndian(a, 8);
        if (x1 < 0 || x2 < x1 || y1 < 0 || y2 < y1) {
            return false;
        }
        width = x2 - x1 + 1;
        height = y2 - y1 + 1;
        // color depth
        int bits = a[1];
        int planes = a[63];
        if (planes == 1 && (bits == 1 || bits == 2 || bits == 4 || bits == 8)) {
            // paletted
            bitsPerPixel = bits;
        } else if (planes == 3 && bits == 8) {
            // RGB truecolor
            bitsPerPixel = 24;
        } else {
            return false;
        }
        setPhysicalWidthDpi(getShortLittleEndian(a, 10));
        setPhysicalHeightDpi(getShortLittleEndian(a, 10));
        format = FORMAT_PCX;
        return true;
    }

    private boolean checkPng() throws IOException {
        final byte[] PNG_MAGIC = {0x4e, 0x47, 0x0d, 0x0a, 0x1a, 0x0a};
        byte[] a = new byte[27];
        if (read(a) != 27) {
            return false;
        }
        if (!equals(a, 0, PNG_MAGIC, 0, 6)) {
            return false;
        }
        format = FORMAT_PNG;
        width = getIntBigEndian(a, 14);
        height = getIntBigEndian(a, 18);
        bitsPerPixel = a[22] & 0xff;
        int colorType = a[23] & 0xff;
        if (colorType == 2 || colorType == 6) {
            bitsPerPixel *= 3;
        }
        progressive = (a[26] & 0xff) != 0;
        return true;
    }

    private boolean checkPnm( int id ) throws IOException {
        if (id < 1 || id > 6) {
            return false;
        }
        final int[] PNM_FORMATS = {FORMAT_PBM, FORMAT_PGM, FORMAT_PPM};
        format = PNM_FORMATS[(id - 1) % 3];
        boolean hasPixelResolution = false;
        String s;
        while (true) {
            s = readLine();
            if (s != null) {
                s = s.trim();
            }
            if (s == null || s.length() < 1) {
                continue;
            }
            if (s.charAt(0) == '#') { // comment
                if (collectComments && s.length() > 1) {
                    addComment(s.substring(1));
                }
                continue;
            }
            if (!hasPixelResolution) { // split "343 966" into width=343, height=966
                int spaceIndex = s.indexOf(' ');
                if (spaceIndex == -1) {
                    return false;
                }
                String widthString = s.substring(0, spaceIndex);
                spaceIndex = s.lastIndexOf(' ');
                if (spaceIndex == -1) {
                    return false;
                }
                String heightString = s.substring(spaceIndex + 1);
                try {
                    width = Integer.parseInt(widthString);
                    height = Integer.parseInt(heightString);
                } catch (NumberFormatException nfe) {
                    return false;
                }
                if (width < 1 || height < 1) {
                    return false;
                }
                if (format == FORMAT_PBM) {
                    bitsPerPixel = 1;
                    return true;
                }
                hasPixelResolution = true;
            } else {
                int maxSample;
                try {
                    maxSample = Integer.parseInt(s);
                } catch (NumberFormatException nfe) {
                    return false;
                }
                if (maxSample < 0) {
                    return false;
                }
                for (int i = 0; i < 25; i++) {
                    if (maxSample < (1 << (i + 1))) {
                        bitsPerPixel = i + 1;
                        if (format == FORMAT_PPM) {
                            bitsPerPixel *= 3;
                        }
                        return true;
                    }
                }
                return false;
            }
        }
    }

    private boolean checkPsd() throws IOException {
        byte[] a = new byte[24];
        if (read(a) != a.length) {
            return false;
        }
        final byte[] PSD_MAGIC = {0x50, 0x53};
        if (!equals(a, 0, PSD_MAGIC, 0, 2)) {
            return false;
        }
        format = FORMAT_PSD;
        width = getIntBigEndian(a, 16);
        height = getIntBigEndian(a, 12);
        int channels = getShortBigEndian(a, 10);
        int depth = getShortBigEndian(a, 20);
        bitsPerPixel = channels * depth;
        return (width > 0 && height > 0 && bitsPerPixel > 0 && bitsPerPixel <= 64);
    }

    private boolean checkRas() throws IOException {
        byte[] a = new byte[14];
        if (read(a) != a.length) {
            return false;
        }
        final byte[] RAS_MAGIC = {0x6a, (byte)0x95};
        if (!equals(a, 0, RAS_MAGIC, 0, 2)) {
            return false;
        }
        format = FORMAT_RAS;
        width = getIntBigEndian(a, 2);
        height = getIntBigEndian(a, 6);
        bitsPerPixel = getIntBigEndian(a, 10);
        return (width > 0 && height > 0 && bitsPerPixel > 0 && bitsPerPixel <= 24);
    }

    /**
     * Run over String list, return false if and only if at least one of the arguments equals <code>-c</code>.
     * 
     * @param args string list to check
     * @return <code>true</code> none of the supplied parameters is <code>-c</code>
     */
    private static boolean determineVerbosity( String[] args ) {
        if (args != null && args.length > 0) {
            for (int i = 0; i < args.length; i++) {
                if ("-c".equals(args[i])) {
                    return false;
                }
            }
        }
        return true;
    }

    private static boolean equals( byte[] a1,
                                   int offs1,
                                   byte[] a2,
                                   int offs2,
                                   int num ) {
        while (num-- > 0) {
            if (a1[offs1++] != a2[offs2++]) {
                return false;
            }
        }
        return true;
    }

    /**
     * If {@link #check()} was successful, returns the image's number of bits per pixel. Does not include transparency information
     * like the alpha channel.
     * 
     * @return number of bits per image pixel
     */
    public int getBitsPerPixel() {
        return bitsPerPixel;
    }

    /**
     * Returns the index'th comment retrieved from the file.
     * 
     * @param index int index of comment to return
     * @return the comment at the supplied index
     * @throws IllegalArgumentException if index is smaller than 0 or larger than or equal to the number of comments retrieved
     * @see #getNumberOfComments
     */
    public String getComment( int index ) {
        if (comments == null || index < 0 || index >= comments.size()) {
            throw new IllegalArgumentException("Not a valid comment index: " + index);
        }
        return comments.elementAt(index);
    }

    /**
     * If {@link #check()} was successful, returns the image format as one of the FORMAT_xyz constants from this class. Use
     * {@link #getFormatName()} to get a textual description of the file format.
     * 
     * @return file format as a FORMAT_xyz constant
     */
    public int getFormat() {
        return format;
    }

    /**
     * If {@link #check()} was successful, returns the image format's name. Use {@link #getFormat()} to get a unique number.
     * 
     * @return file format name
     */
    public String getFormatName() {
        if (format >= 0 && format < FORMAT_NAMES.length) {
            return FORMAT_NAMES[format];
        }
        return "?";
    }

    /**
     * If {@link #check()} was successful, returns one the image's vertical resolution in pixels.
     * 
     * @return image height in pixels
     */
    public int getHeight() {
        return height;
    }

    private static int getIntBigEndian( byte[] a,
                                        int offs ) {
        return (a[offs] & 0xff) << 24 | (a[offs + 1] & 0xff) << 16 | (a[offs + 2] & 0xff) << 8 | a[offs + 3] & 0xff;
    }

    private static int getIntLittleEndian( byte[] a,
                                           int offs ) {
        return (a[offs + 3] & 0xff) << 24 | (a[offs + 2] & 0xff) << 16 | (a[offs + 1] & 0xff) << 8 | a[offs] & 0xff;
    }

    /**
     * If {@link #check()} was successful, returns a String with the MIME type of the format.
     * 
     * @return MIME type, e.g. <code>image/jpeg</code>
     */
    public String getMimeType() {
        if (format >= 0 && format < MIME_TYPE_STRINGS.length) {
            if (format == FORMAT_JPEG && progressive) {
                return "image/pjpeg";
            }
            return MIME_TYPE_STRINGS[format];
        }
        return null;
    }

    /**
     * If {@link #check()} was successful and {@link #setCollectComments(boolean)} was called with <code>true</code> as
     * argument, returns the number of comments retrieved from the input image stream / file. Any number &gt;= 0 and smaller than
     * this number of comments is then a valid argument for the {@link #getComment(int)} method.
     * 
     * @return number of comments retrieved from input image
     */
    public int getNumberOfComments() {
        if (comments == null) {
            return 0;
        }
        return comments.size();
    }

    /**
     * Returns the number of images in the examined file. Assumes that <code>setDetermineImageNumber(true);</code> was called
     * before a successful call to {@link #check()}. This value can currently be only different from <code>1</code> for GIF
     * images.
     * 
     * @return number of images in file
     */
    public int getNumberOfImages() {
        return numberOfImages;
    }

    /**
     * Returns the physical height of this image in dots per inch (dpi). Assumes that {@link #check()} was successful. Returns
     * <code>-1</code> on failure.
     * 
     * @return physical height (in dpi)
     * @see #getPhysicalWidthDpi()
     * @see #getPhysicalHeightInch()
     */
    public int getPhysicalHeightDpi() {
        return physicalHeightDpi;
    }

    /**
     * If {@link #check()} was successful, returns the physical width of this image in dpi (dots per inch) or -1 if no value could
     * be found.
     * 
     * @return physical height (in dpi)
     * @see #getPhysicalHeightDpi()
     * @see #getPhysicalWidthDpi()
     * @see #getPhysicalWidthInch()
     */
    public float getPhysicalHeightInch() {
        int h = getHeight();
        int ph = getPhysicalHeightDpi();
        if (h > 0 && ph > 0) {
            return ((float)h) / ((float)ph);
        }
        return -1.0f;
    }

    /**
     * If {@link #check()} was successful, returns the physical width of this image in dpi (dots per inch) or -1 if no value could
     * be found.
     * 
     * @return physical width (in dpi)
     * @see #getPhysicalHeightDpi()
     * @see #getPhysicalWidthInch()
     * @see #getPhysicalHeightInch()
     */
    public int getPhysicalWidthDpi() {
        return physicalWidthDpi;
    }

    /**
     * Returns the physical width of an image in inches, or <code>-1.0f</code> if width information is not available. Assumes
     * that {@link #check} has been called successfully.
     * 
     * @return physical width in inches or <code>-1.0f</code> on failure
     * @see #getPhysicalWidthDpi
     * @see #getPhysicalHeightInch
     */
    public float getPhysicalWidthInch() {
        int w = getWidth();
        int pw = getPhysicalWidthDpi();
        if (w > 0 && pw > 0) {
            return ((float)w) / ((float)pw);
        }
        return -1.0f;
    }

    private static int getShortBigEndian( byte[] a,
                                          int offs ) {
        return (a[offs] & 0xff) << 8 | (a[offs + 1] & 0xff);
    }

    private static int getShortLittleEndian( byte[] a,
                                             int offs ) {
        return (a[offs] & 0xff) | (a[offs + 1] & 0xff) << 8;
    }

    /**
     * If {@link #check()} was successful, returns one the image's horizontal resolution in pixels.
     * 
     * @return image width in pixels
     */
    public int getWidth() {
        return width;
    }

    /**
     * Returns whether the image is stored in a progressive (also called: interlaced) way.
     * 
     * @return true for progressive/interlaced, false otherwise
     */
    public boolean isProgressive() {
        return progressive;
    }

    /**
     * To use this class as a command line application, give it either some file names as parameters (information on them will be
     * printed to standard output, one line per file) or call it with no parameters. It will then check data given to it via
     * standard input.
     * 
     * @param args the program arguments which must be file names
     */
    public static void main( String[] args ) {
        ImageMetadata imageMetadata = new ImageMetadata();
        imageMetadata.setDetermineImageNumber(true);
        boolean verbose = determineVerbosity(args);
        if (args.length == 0) {
            run(null, System.in, imageMetadata, verbose);
        } else {
            int index = 0;
            while (index < args.length) {
                InputStream in = null;
                try {
                    String name = args[index++];
                    System.out.print(name + ";");
                    if (name.startsWith("http://")) {
                        in = new URL(name).openConnection().getInputStream();
                    } else {
                        in = new FileInputStream(name);
                    }
                    run(name, in, imageMetadata, verbose);
                    in.close();
                } catch (IOException e) {
                    System.out.println(e);
                    try {
                        if (in != null) {
                            in.close();
                        }
                    } catch (IOException ee) {
                    }
                }
            }
        }
    }

    private static void print( String sourceName,
                               ImageMetadata ii,
                               boolean verbose ) {
        if (verbose) {
            printVerbose(sourceName, ii);
        } else {
            printCompact(sourceName, ii);
        }
    }

    private static void printCompact( String sourceName,
                                      ImageMetadata imageMetadata ) {
        final String SEP = "\t";
        System.out.println(sourceName + SEP + imageMetadata.getFormatName() + SEP + imageMetadata.getMimeType() + SEP
                           + imageMetadata.getWidth() + SEP + imageMetadata.getHeight() + SEP + imageMetadata.getBitsPerPixel()
                           + SEP + imageMetadata.getNumberOfImages() + SEP + imageMetadata.getPhysicalWidthDpi() + SEP
                           + imageMetadata.getPhysicalHeightDpi() + SEP + imageMetadata.getPhysicalWidthInch() + SEP
                           + imageMetadata.getPhysicalHeightInch() + SEP + imageMetadata.isProgressive());
    }

    private static void printLine( int indentLevels,
                                   String text,
                                   float value,
                                   float minValidValue ) {
        if (value < minValidValue) {
            return;
        }
        printLine(indentLevels, text, Float.toString(value));
    }

    private static void printLine( int indentLevels,
                                   String text,
                                   int value,
                                   int minValidValue ) {
        if (value >= minValidValue) {
            printLine(indentLevels, text, Integer.toString(value));
        }
    }

    private static void printLine( int indentLevels,
                                   String text,
                                   String value ) {
        if (value == null || value.length() == 0) {
            return;
        }
        while (indentLevels-- > 0) {
            System.out.print("\t");
        }
        if (text != null && text.length() > 0) {
            System.out.print(text);
            System.out.print(" ");
        }
        System.out.println(value);
    }

    private static void printVerbose( String sourceName,
                                      ImageMetadata ii ) {
        printLine(0, null, sourceName);
        printLine(1, "File format: ", ii.getFormatName());
        printLine(1, "MIME type: ", ii.getMimeType());
        printLine(1, "Width (pixels): ", ii.getWidth(), 1);
        printLine(1, "Height (pixels): ", ii.getHeight(), 1);
        printLine(1, "Bits per pixel: ", ii.getBitsPerPixel(), 1);
        printLine(1, "Progressive: ", ii.isProgressive() ? "yes" : "no");
        printLine(1, "Number of images: ", ii.getNumberOfImages(), 1);
        printLine(1, "Physical width (dpi): ", ii.getPhysicalWidthDpi(), 1);
        printLine(1, "Physical height (dpi): ", ii.getPhysicalHeightDpi(), 1);
        printLine(1, "Physical width (inches): ", ii.getPhysicalWidthInch(), 1.0f);
        printLine(1, "Physical height (inches): ", ii.getPhysicalHeightInch(), 1.0f);
        int numComments = ii.getNumberOfComments();
        printLine(1, "Number of textual comments: ", numComments, 1);
        if (numComments > 0) {
            for (int i = 0; i < numComments; i++) {
                printLine(2, null, ii.getComment(i));
            }
        }
    }

    private int read() throws IOException {
        if (in != null) {
            return in.read();
        }
        return din.readByte();
    }

    private int read( byte[] a ) throws IOException {
        if (in != null) {
            return in.read(a);
        }
        din.readFully(a);
        return a.length;
    }

    private int read( byte[] a,
                      int offset,
                      int num ) throws IOException {
        if (in != null) {
            return in.read(a, offset, num);
        }
        din.readFully(a, offset, num);
        return num;
    }

    private String readLine() throws IOException {
        return readLine(new StringBuffer());
    }

    private String readLine( StringBuffer sb ) throws IOException {
        boolean finished;
        do {
            int value = read();
            finished = (value == -1 || value == 10);
            if (!finished) {
                sb.append((char)value);
            }
        } while (!finished);
        return sb.toString();
    }

    private static void run( String sourceName,
                             InputStream in,
                             ImageMetadata imageMetadata,
                             boolean verbose ) {
        imageMetadata.setInput(in);
        imageMetadata.setDetermineImageNumber(true);
        imageMetadata.setCollectComments(verbose);
        if (imageMetadata.check()) {
            print(sourceName, imageMetadata, verbose);
        }
    }

    /**
     * Specify whether textual comments are supposed to be extracted from input. Default is <code>false</code>. If enabled,
     * comments will be added to an internal list.
     * 
     * @param newValue if <code>true</code>, this class will read comments
     * @see #getNumberOfComments
     * @see #getComment
     */
    public void setCollectComments( boolean newValue ) {
        collectComments = newValue;
    }

    /**
     * Specify whether the number of images in a file is to be determined - default is <code>false</code>. This is a special
     * option because some file formats require running over the entire file to find out the number of images, a rather
     * time-consuming task. Not all file formats support more than one image. If this method is called with <code>true</code> as
     * argument, the actual number of images can be queried via {@link #getNumberOfImages()} after a successful call to
     * {@link #check()}.
     * 
     * @param newValue will the number of images be determined?
     * @see #getNumberOfImages
     */
    public void setDetermineImageNumber( boolean newValue ) {
        determineNumberOfImages = newValue;
    }

    /**
     * Set the input stream to the argument stream (or file). Note that {@link java.io.RandomAccessFile} implements
     * {@link java.io.DataInput}.
     * 
     * @param dataInput the input stream to read from
     */
    public void setInput( DataInput dataInput ) {
        din = dataInput;
        in = null;
    }

    /**
     * Set the input stream to the argument stream (or file).
     * 
     * @param inputStream the input stream to read from
     */
    public void setInput( InputStream inputStream ) {
        in = inputStream;
        din = null;
    }

    private void setPhysicalHeightDpi( int newValue ) {
        physicalWidthDpi = newValue;
    }

    private void setPhysicalWidthDpi( int newValue ) {
        physicalHeightDpi = newValue;
    }

    private void skip( int num ) throws IOException {
        while (num > 0) {
            long result;
            if (in != null) {
                result = in.skip(num);
            } else {
                result = din.skipBytes(num);
            }
            if (result > 0) {
                num -= result;
            } else {
                if (in != null) {
                    result = in.read();
                } else {
                    result = din.readByte();
                }
                if (result == -1) {
                    throw new IOException("Premature end of input.");
                }
                num--;
            }
        }
    }
}
