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## Class ImageInfo

    java.lang.Object
      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 2003-07-28.

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.

Field Summary
`static int` | `COLOR_TYPE_BLACK_AND_WHITE`
`static int` | `COLOR_TYPE_GRAYSCALE`
`static int` | `COLOR_TYPE_PALETTED`
`static int` | `COLOR_TYPE_TRUECOLOR_RGB`
`static int` | `COLOR_TYPE_UNKNOWN`
`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.

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 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_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

### COLOR_TYPE_UNKNOWN

    public static final int COLOR_TYPE_UNKNOWN

See Also:
  Constant Field Values

### COLOR_TYPE_TRUECOLOR_RGB

    public static final int COLOR_TYPE_TRUECOLOR_RGB

See Also:
  Constant Field Values

### COLOR_TYPE_PALETTED

    public static final int COLOR_TYPE_PALETTED

See Also:
  Constant Field Values

### COLOR_TYPE_GRAYSCALE

    public static final int COLOR_TYPE_GRAYSCALE

See Also:
  Constant Field Values

### COLOR_TYPE_BLACK_AND_WHITE

    public static final int COLOR_TYPE_BLACK_AND_WHITE

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 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

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