com.jalios.io

Class ImageInfo

java.lang.Object

com.jalios.io.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.

Version:

$Revision: 27751 $

Field Summary

Fields

Modifier and Type	Field and Description
static int	FORMAT_BMP Return value of getFormat() for BMP streams.
static int	FORMAT_GIF Return value of getFormat() for GIF streams.
static int	FORMAT_IFF Return value of getFormat() for IFF streams.
static int	FORMAT_JPEG Return value of getFormat() for JPEG streams.
static int	FORMAT_PBM Return value of getFormat() for PBM streams.
static int	FORMAT_PCX Return value of getFormat() for PCX streams.
static int	FORMAT_PGM Return value of getFormat() for PGM streams.
static int	FORMAT_PNG Return value of getFormat() for PNG streams.
static int	FORMAT_PPM Return value of getFormat() for PPM streams.
static int	FORMAT_PSD Return value of getFormat() for PSD streams.
static int	FORMAT_RAS Return value of getFormat() for RAS streams.
static int	FORMAT_SWF Return value of getFormat() for SWF (Shockwave) streams.
static java.lang.String	REVISION

Constructor Summary

Constructors

Constructor and Description
ImageInfo()

Method Summary

Methods

Modifier and Type	Method and 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

REVISION

public static final java.lang.String REVISION

See Also:

Constant Field Values

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_IFF

public static final int FORMAT_IFF

Return value of getFormat() for IFF streams.

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

FORMAT_PBM

public static final int FORMAT_PBM

Return value of getFormat() for PBM streams.

See Also:

Constant Field Values

FORMAT_PGM

public static final int FORMAT_PGM

Return value of getFormat() for PGM streams.

See Also:

Constant Field Values

FORMAT_PPM

public static final int FORMAT_PPM

Return value of getFormat() for PPM streams.

See Also:

Constant Field Values

FORMAT_PSD

public static final int FORMAT_PSD

Return value of getFormat() for PSD streams.

See Also:

Constant Field Values

FORMAT_SWF

public static final int FORMAT_SWF

Return value of getFormat() for SWF (Shockwave) streams.

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()

getPhysicalHeightInch

public 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.

Returns:

physical height (in dpi)

See Also:

getPhysicalHeightDpi(), getPhysicalWidthDpi(), getPhysicalWidthInch()

getPhysicalWidthDpi

public 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.

Returns:

physical width (in dpi)

See Also:

getPhysicalHeightDpi(), getPhysicalWidthInch(), 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