org.devlib.schmidt.imageinfo
Class ImageInfo

java.lang.Object
  org.devlib.schmidt.imageinfo.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 and PSD 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).");
  // there are other properties, check out the API documentation
 

You can also use this class as a command line program. Call it with a number of image file names and URLs as parameters:

   java ImageInfo *.jpg *.png *.gif http://somesite.tld/image.jpg
 

or call it without parameters and pipe data to it:

   java ImageInfo < image.jpg  
 

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://schmidt.devlib.org/image-info/.

Written by Marco Schmidt.

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

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.
• 2003-07-28 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.
• 2004-02-29 Added support for recognizing progressive JPEG and interlaced PNG and GIF. A new method isProgressive() returns whether ImageInfo 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.
• 2004-11-30 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 ImageInfo is used for the "progressive" status.
• 2005-01-02 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 'Known issues' section of the website. Released as 1.6.
• 2005-07-26 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 ImageInfo class to org.devlib.schmidt.imageinfo (a package was repeatedly requested by some users). Released as 1.7.
• 2006-02-23 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.
• 2006-11-13 Removed check that made ImageInfo 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.

Author:

Marco Schmidt

Field Summary

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.

Constructor Summary

ImageInfo()

Method Summary

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 file.
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.
boolean	isProgressive() Returns whether the image is stored in a progressive (also called: interlaced) way.
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.
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).

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. It is determined whether the JPEG stream is progressive (see isProgressive()).

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). It is determined whether the GIF stream is interlaced (see isProgressive()).

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. It is determined whether the PNG stream is interlaced (see isProgressive()).

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.

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

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 information on the file's 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 file.

Parameters:

index - int index of comment to return

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

isProgressive

public boolean isProgressive()

Returns whether the image is stored in a progressive (also called: interlaced) way.

Returns:

true for progressive/interlaced, false otherwise

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

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