java.lang.Object
- net.sourceforge.jiu.ops.Operation
- - net.sourceforge.jiu.codecs.ImageCodec
  - - net.sourceforge.jiu.codecs.GIFCodec

```
public class GIFCodec
extends ImageCodec
```
A codec to write Compuserve GIF (Graphics Interchange Format) files.
Only writing GIF files is supported right now. Reading GIF files with JIU can be done with the ToolkitLoader class which uses the image reader built into the Java runtime library (Toolkit class). That reader has supported GIF since Java 1.0.
Supported image types
When saving, classes implementing the following image data interfaces are supported: BilevelImage, Gray8Image and Paletted8Image. GIF only supports up to 256 colors in an image, so you will have to use one of the quantization classes to reduce a truecolor image to 256 or less colors before you can save it with this codec.
Supported I/O classes
This codec supports OutputStream, DataOutput and RandomAccessFile.
Bounds
ImageCodec's bounds concept is supported. A user of this codec can specify a rectangular part of the input image that will be saved instead of the complete image.
Comments
GIF - at least in its 89a version - allows for the inclusion of textual comments. When saving an image to a GIF file, each comment given to a codec will be stored in a comment extension block of its own.
Usage example
Save an image using this codec:
```
 GIFCodec codec = new GIFCodec();
 codec.appendComment("Bob and Susan at the Munich airport (2002-06-13).");
 codec.setImage(image); // BilevelImage, Gray8Image or Paletted8Image
 codec.setInterlacing(true);
 codec.setFile("output.gif", CodecMode.SAVE);
 codec.process();
 codec.close();
 
```
Interlaced storage
This codec allows creating interlaced and non-interlaced GIF files. The default is non-interlaced storage. Non-interlaced files store the rows top-to-bottom.
Interlaced files store the image in four passes, progressively adding rows until the complete image is stored. When decoding, the progressive display of interlaced files makes it supposedly quicker to find out what's displayed in the image.
On the other hand, transmission typically takes longer, because interlacing often leads to slightly larger files. When using interlaced mode, lines that get stored one after another have some room between them in the image, so there are less similarities between consecutive lines, which worsens compression ratio (compression works better with a lot of similarities in the data to be compressed).
GIF versions
There are two versions of GIF, 87a and 89a. In 89a, several things were added to the file format specification. From the 89a features this codec only uses the possibility of storing textual comments in GIF files. Thus, the version used for writing depends on the return value of ImageCodec.getNumComments(). If there is at least one comment to be written to the file, version 89a will be used, 87a otherwise.
Licensing of the LZW algorithm
Unisys Corp. had a patent in several countries on the LZW algorithm used within GIF. However, this patent has expired (Japan being the last country where the patent expired, on July 7th 2004) so that LZW can be used freely.
Licensing of the file format
GIF was defined by Compuserve. In a technical document file called Gif89a.txt that I found somewhere on the Net they grant a royalty-free license for use of the format to anyone - in order to improve the popularity of the format, I guess. I don't think that it should be possible to put a file format under a copyright, but all that Compuserve asks for in exchange for freely using the format is the inclusion of a message. So, here is that message:
"The Graphics Interchange Format(c) is the Copyright property of CompuServe Incorporated. GIF(sm) is a Service Mark property of CompuServe Incorporated."

Animated GIFs
GIF allows for animations to be stored. This codec only supports storing a single image, though.
File format background
I've compiled a web page with technical information on GIF.
Author:

Marco Schmidt

Field Summary

Fields
Modifier and Type	Field	Description
`private int`	`backgroundColor`
`private int`	`bitOffset`
`private int`	`bitsPerPixel`
`private byte[]`	`block`
`private int`	`blockLength`
`private int`	`clearCode`
`private static int`	`CODE_ARRAY_LENGTH`
`private int`	`codeSize`
`private int[]`	`currentCode`
`private int`	`currentColumn`
`private int`	`currentInterlacingPass`
`private int`	`currentRow`
`private int`	`endOfInformationCode`
`private int`	`freeCode`
`private int`	`height`
`private IntegerImage`	`imageToBeSaved`
`private int`	`initialCodeSize`
`private boolean`	`interlaced`
`private static int[]`	`INTERLACING_FIRST_ROW`
`private static int[]`	`INTERLACING_INCREMENT`
`private static byte[]`	`MAGIC_GIF87A`
`private static byte[]`	`MAGIC_GIF89A`
`private int`	`maxCode`
`private int[]`	`newCode`
`private boolean`	`notFinished`
`private static int`	`NUM_INTERLACING_PASSES`
`private int[]`	`oldCode`
`private DataOutput`	`out`
`private int`	`processedRows`
`private int`	`width`

Constructor Summary

Constructors
Constructor Description

GIFCodec()

Method Summary

All Methods Instance Methods Concrete Methods
Modifier and Type	Method	Description
`int`	`getBackgroundColor()`	Returns the index of the background color.
`String[]`	`getFileExtensions()`	Returns all file extensions that are typical for this file format.
`String`	`getFormatName()`	Returns the name of the file format supported by this codec.
`String[]`	`getMimeTypes()`	Return the MIME (Multipurpose Internet Mail Extensions) type strings for this format, or `null` if none are available.
`private int`	`getNextSample()`
`private void`	`initEncoding()`
`boolean`	`isInterlaced()`	Returns if the image will be stored in interlaced (`true`) or non-interlaced mode (`false`).
`boolean`	`isLoadingSupported()`	Returns if this codec is able to load images in the file format supported by this codec.
`boolean`	`isSavingSupported()`	Returns if this codec is able to save images in the file format supported by this codec.
`void`	`process()`	This method does the actual work of the operation.
`private void`	`resetBlock()`
`private void`	`resetEncoder()`
`private void`	`save()`
`void`	`setBackgroundColor(int colorIndex)`	Specify the value of the background color.
`void`	`setInterlacing(boolean useInterlacing)`	Specifies whether the image will be stored in interlaced mode (`true`) or non-interlaced mode (`false`).
`private void`	`writeBlock()`
`private void`	`writeCode(int code)`
`private void`	`writeComments()`
`private void`	`writeHeader()`	Writes a global header, a global palette and an image descriptor to output.
`private void`	`writeImage()`
`private void`	`writePalette()`
`private void`	`writeShort(int value)`
`private void`	`writeStream()`
`private void`	`writeTrailer()`

Methods inherited from class net.sourceforge.jiu.codecs.ImageCodec
appendComment, checkBounds, checkImageResolution, close, getBoundsHeight, getBoundsWidth, getBoundsX1, getBoundsX2, getBoundsY1, getBoundsY2, getComment, getDataInput, getDataOutput, getDpiX, getDpiY, getImage, getImageIndex, getInputAsDataInput, getInputStream, getMode, getNumComments, getOutputAsDataOutput, getOutputStream, getRandomAccessFile, hasBounds, initModeFromIOObjects, isRowRequired, isTileRequired, removeAllComments, removeBounds, setBounds, setBoundsIfNecessary, setDataInput, setDataOutput, setDpi, setFile, setFile, setImage, setImageIndex, setInputStream, setOutputStream, setRandomAccessFile, suggestFileExtension

Methods inherited from class net.sourceforge.jiu.ops.Operation
addProgressListener, addProgressListeners, getAbort, removeProgressListener, setAbort, setProgress, setProgress

Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

- Field Detail
  - CODE_ARRAY_LENGTH
```
private static final int CODE_ARRAY_LENGTH
```
    See Also:
    
    Constant Field Values
  - INTERLACING_FIRST_ROW
```
private static final int[] INTERLACING_FIRST_ROW
```
  - INTERLACING_INCREMENT
```
private static final int[] INTERLACING_INCREMENT
```
  - NUM_INTERLACING_PASSES
```
private static final int NUM_INTERLACING_PASSES
```
    See Also:
    
    Constant Field Values
  - MAGIC_GIF87A
```
private static final byte[] MAGIC_GIF87A
```
  - MAGIC_GIF89A
```
private static final byte[] MAGIC_GIF89A
```
  - backgroundColor
```
private int backgroundColor
```
  - block
```
private byte[] block
```
  - bitOffset
```
private int bitOffset
```
  - bitsPerPixel
```
private int bitsPerPixel
```
  - blockLength
```
private int blockLength
```
  - clearCode
```
private int clearCode
```
  - codeSize
```
private int codeSize
```
  - currentCode
```
private int[] currentCode
```
  - currentColumn
```
private int currentColumn
```
  - currentInterlacingPass
```
private int currentInterlacingPass
```
  - currentRow
```
private int currentRow
```
  - endOfInformationCode
```
private int endOfInformationCode
```
  - notFinished
```
private boolean notFinished
```
  - freeCode
```
private int freeCode
```
  - imageToBeSaved
```
private IntegerImage imageToBeSaved
```
  - initialCodeSize
```
private int initialCodeSize
```
  - interlaced
```
private boolean interlaced
```
  - height
```
private int height
```
  - maxCode
```
private int maxCode
```
  - newCode
```
private int[] newCode
```
  - oldCode
```
private int[] oldCode
```
  - out
```
private DataOutput out
```
  - processedRows
```
private int processedRows
```
  - width
```
private int width
```
- Constructor Detail
  - GIFCodec
```
public GIFCodec()
```
- Method Detail
  - getBackgroundColor
```
public int getBackgroundColor()
```
    Returns the index of the background color.
    
    Returns:
    
    int value with the color (index into the palette) of the background color
    
    See Also:
    
    setBackgroundColor(int)
  - getFileExtensions
```
public String[] getFileExtensions()
```
    Description copied from class: ImageCodec
    
    Returns all file extensions that are typical for this file format. The default implementation in ImageCodec returns null. The file extension strings should include a leading dot and are supposed to be lower case (if that is allowed for the given file format). Example: {".jpg", ".jpeg"} for the JPEG file format.
    
    Overrides:
    
    getFileExtensions in class ImageCodec
    
    Returns:
    
    String array with typical file extensions
  - getFormatName
```
public String getFormatName()
```
    Description copied from class: ImageCodec
    
    Returns the name of the file format supported by this codec. All classes extending ImageCodec must override this method. When overriding, leave out any words in a particular language so that this format name can be understood by everyone. Usually it is enough to return the format creator plus a typical abbreviation, e.g. Microsoft BMP or Portable Anymap (PNM).
    
    Specified by:
    
    getFormatName in class ImageCodec
    
    Returns:
    
    name of the file format supported by this codec
  - getMimeTypes
```
public String[] getMimeTypes()
```
    Description copied from class: ImageCodec
    
    Return the MIME (Multipurpose Internet Mail Extensions) type strings for this format, or null if none are available.
    
    Specified by:
    
    getMimeTypes in class ImageCodec
    
    Returns:
    
    MIME type strings or null
  - getNextSample
```
private int getNextSample()
```
  - initEncoding
```
private void initEncoding()
                   throws IOException
```
    Throws:
    
    IOException
  - isInterlaced
```
public boolean isInterlaced()
```
    Returns if the image will be stored in interlaced (true) or non-interlaced mode (false).
    
    Returns:
    
    interlacing mode
    
    See Also:
    
    setInterlacing(boolean)
  - isLoadingSupported
```
public boolean isLoadingSupported()
```
    Description copied from class: ImageCodec
    
    Returns if this codec is able to load images in the file format supported by this codec. If true is returned this does not necessarily mean that all files in this format can be read, but at least some.
    
    Specified by:
    
    isLoadingSupported in class ImageCodec
    
    Returns:
    
    if loading is supported
  - isSavingSupported
```
public boolean isSavingSupported()
```
    Description copied from class: ImageCodec
    
    Returns if this codec is able to save images in the file format supported by this codec. If true is returned this does not necessarily mean that all types files in this format can be written, but at least some.
    
    Specified by:
    
    isSavingSupported in class ImageCodec
    
    Returns:
    
    if saving is supported
  - process
```
public void process()
             throws MissingParameterException,
                    OperationFailedException
```
    Description copied from class: Operation
    
    This method does the actual work of the operation. It must be called after all parameters have been given to the operation object.
    
    Overrides:
    
    process in class Operation
    
    Throws:
    
    MissingParameterException - if any mandatory parameter was not given to the operation
    
    WrongParameterException - if at least one of the input parameters was not initialized appropriately (values out of the valid interval, etc.)
    
    OperationFailedException
  - resetBlock
```
private void resetBlock()
```
  - resetEncoder
```
private void resetEncoder()
```
  - save
```
private void save()
           throws MissingParameterException,
                  OperationFailedException,
                  UnsupportedTypeException,
                  WrongParameterException
```
    Throws:
    
    MissingParameterException
    
    OperationFailedException
    
    UnsupportedTypeException
    
    WrongParameterException
  - setBackgroundColor
```
public void setBackgroundColor(int colorIndex)
```
    Specify the value of the background color. Default is 0.
    
    Parameters:
    
    colorIndex - int value with the color (index into the palette) of the background color
    
    See Also:
    
    getBackgroundColor()
  - setInterlacing
```
public void setInterlacing(boolean useInterlacing)
```
    Specifies whether the image will be stored in interlaced mode (true) or non-interlaced mode (false).
    
    Parameters:
    
    useInterlacing - boolean, if true interlaced mode, otherwise non-interlaced mode
    
    See Also:
    
    isInterlaced()
  - writeBlock
```
private void writeBlock()
                 throws IOException
```
    Throws:
    
    IOException
  - writeCode
```
private void writeCode(int code)
                throws IOException
```
    Throws:
    
    IOException
  - writeComments
```
private void writeComments()
                    throws IOException
```
    Throws:
    
    IOException
  - writeHeader
```
private void writeHeader()
                  throws IOException
```
    Writes a global header, a global palette and an image descriptor to output.
    
    Throws:
    
    IOException
  - writeImage
```
private void writeImage()
                 throws IOException
```
    Throws:
    
    IOException
  - writePalette
```
private void writePalette()
                   throws IOException
```
    Throws:
    
    IOException
  - writeShort
```
private void writeShort(int value)
                 throws IOException
```
    Throws:
    
    IOException
  - writeStream
```
private void writeStream()
                  throws IOException
```
    Throws:
    
    IOException
  - writeTrailer
```
private void writeTrailer()
                   throws IOException
```
    Throws:
    
    IOException

Class GIFCodec

Supported image types

Supported I/O classes

Bounds

Comments

Usage example

Interlaced storage

GIF versions

Licensing of the LZW algorithm

Licensing of the file format

Animated GIFs

File format background

Field Summary

Constructor Summary

Method Summary

Methods inherited from class net.sourceforge.jiu.codecs.ImageCodec

Methods inherited from class net.sourceforge.jiu.ops.Operation

Methods inherited from class java.lang.Object

Field Detail

CODE_ARRAY_LENGTH

INTERLACING_FIRST_ROW

INTERLACING_INCREMENT

NUM_INTERLACING_PASSES

MAGIC_GIF87A

MAGIC_GIF89A

backgroundColor

block

bitOffset

bitsPerPixel

blockLength

clearCode

codeSize

currentCode

currentColumn

currentInterlacingPass

currentRow

endOfInformationCode

notFinished

freeCode

imageToBeSaved

initialCodeSize

interlaced

height

maxCode

newCode

oldCode

out

processedRows

width

Constructor Detail

GIFCodec

Method Detail

getBackgroundColor

getFileExtensions

getFormatName

getMimeTypes

getNextSample

initEncoding

isInterlaced

isLoadingSupported

isSavingSupported

process

resetBlock

resetEncoder

save

setBackgroundColor

setInterlacing

writeBlock

writeCode

writeComments

writeHeader

writeImage

writePalette

writeShort

writeStream

writeTrailer