Package com.jalios.io

Class ImageInfo

  • public class ImageInfo
extends java.lang.Object
    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, PSD and SWF files (or input streams).

    Use the class like this: 

     ImageInfo ii = new ImageInfo();
 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("Not a supported image file format.");
   return;
 }
 System.out.println(ii.getFormatName() + ", " + ii.getMimeType() + 
   ", " + ii.getWidth() + " x " + ii.getHeight() + " pixels, " + 
   ii.getBitsPerPixel() + " bits per pixel, " + ii.getNumberOfImages() +
   " image(s), " + ii.getNumberOfComments() + " comment(s).");
    You can also use this class as a command line program. Call it with a number of image file names as parameters: 
       java ImageInfo *.jpg *.png *.gif
    or call it without parameters and pipe data to it: 
       cat image.jpg | java ImageInfo

    Known limitations:

    • 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.
    • 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! ;-)

    Requirements:

    • Java 1.1 or higher

    The latest version can be found at http://www.geocities.com/marcoschmidt.geo/image-info.html.

    Written by Marco Schmidt.

    This class is contributed to the Public Domain. Use it at your own risk.

    Last modification 2002-06-17.

    History:

    • 2001-08-24 Initial version.
    • 2001-10-13 Added support for the file formats BMP and PCX.
    • 2001-10-16 Fixed bug in read(int[], int, int) that returned
    • 2002-01-22 Added support for file formats Amiga IFF and Sun Raster (RAS).
    • 2002-01-24 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.
    • 2002-03-15 Added support to recognize number of images in file. Only works with GIF. Use setDetermineImageNumber(boolean) with true as argument to identify animated GIFs (getNumberOfImages() will return a value larger than 1).
    • 2002-04-10 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.
    • 2002-04-18 Added 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: getPhysicalWidthDpi() and getPhysicalHeightDpi(). If the physical resolution could not be retrieved, these methods return -1.
    • 2002-04-23 Added support for the new properties physical resolution and comments for some formats. Released as 1.2.
    • 2002-06-17 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.

    • Constructor Summary

      Constructors 
      Constructor Description
      ImageInfo()  

    • Method Summary

      All Methods Static Methods Instance Methods Concrete Methods 
      Modifier and Type Method Description
      boolean check()
      Call this method after you have provided an input stream or file using setInput(InputStream) or setInput(DataInput).
      int getBitsPerPixel()
      If check() was successful, returns the image's number of bits per pixel.
      java.lang.String getComment​(int index)
      Returns the index'th comment retrieved from the image.
      int getFormat()
      If check() was successful, returns the image format as one of the FORMAT_xyz constants from this class.
      java.lang.String getFormatName()
      If check() was successful, returns the image format's name.
      int getHeight()
      If check() was successful, returns one the image's vertical resolution in pixels.
      java.lang.String getMimeType()
      If check() was successful, returns a String with the MIME type of the format.
      int getNumberOfComments()
      If check() was successful and setCollectComments(boolean) was called with true as argument, returns the number of comments retrieved from the input image stream / file.
      int getNumberOfImages()
      Returns the number of images in the examined file.
      int getPhysicalHeightDpi()
      Returns the physical height of this image in dots per inch (dpi).
      float getPhysicalHeightInch()
      If check() was successful, returns the physical width of this image in dpi (dots per inch) or -1 if no value could be found.
      int getPhysicalWidthDpi()
      If check() was successful, returns the physical width of this image in dpi (dots per inch) or -1 if no value could be found.
      float getPhysicalWidthInch()
      Returns the physical width of an image in inches, or -1.0f if width information is not available.
      int getWidth()
      If check() was successful, returns one the image's horizontal resolution in pixels.
      static void main​(java.lang.String[] args)
      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.
      long readUBits​(int numBits)
      Read an unsigned value from the given number of bits
      void setCollectComments​(boolean newValue)
      Specify whether textual comments are supposed to be extracted from input.
      void setDetermineImageNumber​(boolean newValue)
      Specify whether the number of images in a file is to be determined - default is false.
      void setInput​(java.io.DataInput dataInput)
      Set the input stream to the argument stream (or file).
      void setInput​(java.io.InputStream inputStream)
      Set the input stream to the argument stream (or file).
      void synchBits()
      Reset the bit buffer

      • Methods inherited from class java.lang.Object

        clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

    • Field Detail

      • FORMAT_JPEG

        public static final int FORMAT_JPEG
        Return value of getFormat() for JPEG streams. ImageInfo can extract physical resolution and comments from JPEGs (only from APP0 headers). Only one image can be stored in a file.
        See Also:
        Constant Field Values

      • FORMAT_GIF

        public static final int FORMAT_GIF
        Return value of getFormat() for GIF streams. ImageInfo can extract comments from GIFs and count the number of images (GIFs with more than one image are animations). If you know of a place where GIFs store the physical resolution of an image, please send me a mail!
        See Also:
        Constant Field Values

      • FORMAT_PNG

        public static final int FORMAT_PNG
        Return value of getFormat() for PNG streams. PNG only supports one image per file. Both physical resolution and comments can be stored with PNG, but ImageInfo is currently not able to extract those.
        See Also:
        Constant Field Values

      • FORMAT_BMP

        public static final int FORMAT_BMP
        Return value of getFormat() for BMP streams. BMP only supports one image per file. BMP does not allow for comments. The physical resolution can be stored. The specification that I have says that the values must be interpreted as dots per meter. However, given that I only encounter typical dpi values like 72 or 300, I currently consider those values dpi. Maybe someone can shed some light on this, please send me a mail in that case.
        See Also:
        Constant Field Values

      • FORMAT_PCX

        public static final int FORMAT_PCX
        Return value of getFormat() for PCX streams. PCX does not allow for comments or more than one image per file. However, the physical resolution can be stored.
        See Also:
        Constant Field Values

      • FORMAT_RAS

        public static final int FORMAT_RAS
        Return value of getFormat() for RAS streams. Sun Raster allows for one image per file only and is not able to store physical resolution or comments.
        See Also:
        Constant Field Values

    • Constructor Detail

      • ImageInfo

        public ImageInfo()

    • Method Detail

      • check

        public boolean check()
        Call this method after you have provided an input stream or file using setInput(InputStream) or setInput(DataInput). If true is returned, the file format was known and you information about its content can be retrieved using the various getXyz methods.
        Returns:
        if information could be retrieved from input

      • getBitsPerPixel

        public int getBitsPerPixel()
        If check() was successful, returns the image's number of bits per pixel. Does not include transparency information like the alpha channel.
        Returns:
        number of bits per image pixel

      • getComment

        public java.lang.String getComment​(int index)
        Returns the index'th comment retrieved from the image.
        Throws:
        java.lang.IllegalArgumentException - if index is smaller than 0 or larger than or equal to the number of comments retrieved
        See Also:
        getNumberOfComments()

      • getFormat

        public int getFormat()
        If check() was successful, returns the image format as one of the FORMAT_xyz constants from this class. Use getFormatName() to get a textual description of the file format.
        Returns:
        file format as a FORMAT_xyz constant

      • getFormatName

        public java.lang.String getFormatName()
        If check() was successful, returns the image format's name. Use getFormat() to get a unique number.
        Returns:
        file format name

      • getHeight

        public int getHeight()
        If check() was successful, returns one the image's vertical resolution in pixels.
        Returns:
        image height in pixels

      • getMimeType

        public java.lang.String getMimeType()
        If check() was successful, returns a String with the MIME type of the format.
        Returns:
        MIME type, e.g. image/jpeg

      • getNumberOfComments

        public int getNumberOfComments()
        If check() was successful and setCollectComments(boolean) was called with true as argument, returns the number of comments retrieved from the input image stream / file. Any number >= 0 and smaller than this number of comments is then a valid argument for the getComment(int) method.
        Returns:
        number of comments retrieved from input image

      • getNumberOfImages

        public int getNumberOfImages()
        Returns the number of images in the examined file. Assumes that setDetermineImageNumber(true); was called before a successful call to check(). This value can currently be only different from 1 for GIF images.
        Returns:
        number of images in file

      • getPhysicalHeightDpi

        public int getPhysicalHeightDpi()
        Returns the physical height of this image in dots per inch (dpi). Assumes that check() was successful. Returns -1 on failure.
        Returns:
        physical height (in dpi)
        See Also:
        getPhysicalWidthDpi(), getPhysicalHeightInch()

      • getPhysicalWidthInch

        public float getPhysicalWidthInch()
        Returns the physical width of an image in inches, or -1.0f if width information is not available. Assumes that check() has been called successfully.
        Returns:
        physical width in inches or -1.0f on failure
        See Also:
        getPhysicalWidthDpi(), getPhysicalHeightInch()

      • getWidth

        public int getWidth()
        If check() was successful, returns one the image's horizontal resolution in pixels.
        Returns:
        image width in pixels

      • main

        public static void main​(java.lang.String[] args)
        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.
        Parameters:
        args - the program arguments which must be file names

      • readUBits

        public long readUBits​(int numBits)
               throws java.io.IOException
        Read an unsigned value from the given number of bits
        Throws:
        java.io.IOException

      • synchBits

        public void synchBits()
        Reset the bit buffer

      • setCollectComments

        public void setCollectComments​(boolean newValue)
        Specify whether textual comments are supposed to be extracted from input. Default is false. If enabled, comments will be added to an internal list.
        Parameters:
        newValue - if true, this class will read comments
        See Also:
        getNumberOfComments(), getComment(int)

      • setDetermineImageNumber

        public void setDetermineImageNumber​(boolean newValue)
        Specify whether the number of images in a file is to be determined - default is false. 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 true as argument, the actual number of images can be queried via getNumberOfImages() after a successful call to check().
        Parameters:
        newValue - will the number of images be determined?
        See Also:
        getNumberOfImages()

      • setInput

        public void setInput​(java.io.DataInput dataInput)
        Set the input stream to the argument stream (or file). Note that RandomAccessFile implements DataInput.
        Parameters:
        dataInput - the input stream to read from

      • setInput

        public void setInput​(java.io.InputStream inputStream)
        Set the input stream to the argument stream (or file).
        Parameters:
        inputStream - the input stream to read from