GifDecoder

java.lang.Object
- org.opensourcephysics.media.gif.GifDecoder

public class GifDecoder
extends java.lang.Object

Class GifDecoder - Decodes a GIF file into one or more frames.

 Example:
    GifDecoder d = new GifDecoder();
    d.read("sample.gif");
    int n = d.getFrameCount();
    for (int i = 0; i < n; i++) {
       BufferedImage frame = d.getFrame(i);  // frame i
       int t = d.getDelay(i);  // display duration of frame in milliseconds
       // do something with frame
    }

No copyright asserted on the source code of this class. May be used for any purpose, however, refer to the Unisys LZW patent for any additional restrictions. Please forward any corrections to kweiner@fmsware.com.

Field Summary

Fields
Modifier and Type	Field	Description
`protected int[]`	`act`
`protected int`	`bgColor`
`protected int`	`bgIndex`
`protected byte[]`	`block`
`protected int`	`blockSize`
`protected int`	`delay`
`protected int`	`dispose`
`protected int`	`frameCount`
`protected java.util.ArrayList<org.opensourcephysics.media.gif.GifDecoder.GifFrame>`	`frames`
`protected int[]`	`gct`
`protected boolean`	`gctFlag`
`protected int`	`gctSize`
`protected int`	`height`
`protected int`	`ih`
`protected java.awt.image.BufferedImage`	`image`
`protected java.io.BufferedInputStream`	`in`
`protected boolean`	`interlace`
`protected int`	`iw`
`protected int`	`ix`
`protected int`	`iy`
`protected int`	`lastBgColor`
`protected int`	`lastDispose`
`protected java.awt.image.BufferedImage`	`lastImage`
`protected java.awt.Rectangle`	`lastRect`
`protected int[]`	`lct`
`protected boolean`	`lctFlag`
`protected int`	`lctSize`
`protected int`	`loopCount`
`protected static int`	`MaxStackSize`
`protected int`	`pixelAspect`
`protected byte[]`	`pixels`
`protected byte[]`	`pixelStack`
`protected short[]`	`prefix`
`protected int`	`status`
`static int`	`STATUS_FORMAT_ERROR`	File read status: Error decoding file (may be partially decoded)
`static int`	`STATUS_OK`	File read status: No errors.
`static int`	`STATUS_OPEN_ERROR`	File read status: Unable to open source.
`protected byte[]`	`suffix`
`protected int`	`transIndex`
`protected boolean`	`transparency`
`protected int`	`width`

Constructor Summary

Constructors
Constructor Description

GifDecoder()

Constructors
Constructor	Description
`GifDecoder()`

Method Summary

All Methods Instance Methods Concrete Methods
Modifier and Type	Method	Description
`protected void`	`decodeImageData()`	Decodes LZW image data into pixel array.
`protected boolean`	`err()`	Returns true if an error was encountered during reading/decoding
`int`	`getDelay(int n)`	Gets display duration for specified frame.
`java.awt.image.BufferedImage`	`getFrame(int n)`	Gets the image contents of frame n.
`int`	`getFrameCount()`	Gets the number of frames read from file.
`java.awt.Dimension`	`getFrameSize()`	Gets image size.
`java.awt.image.BufferedImage`	`getImage()`	Gets the first (or only) image read.
`int`	`getLoopCount()`	Gets the "Netscape" iteration count, if any.
`protected void`	`init()`	Initializes or re-initializes reader
`protected int`	`read()`	Reads a single byte from the input stream.
`int`	`read(java.io.BufferedInputStream input)`	Reads GIF image from stream
`int`	`read(java.lang.String name)`	Reads GIF file from specified file/URL source (URL assumed if name contains ":/" or "file:")
`protected int`	`readBlock()`	Reads next variable length block from input.
`protected int[]`	`readColorTable(int ncolors)`	Reads color table as 256 RGB integer values
`protected void`	`readContents()`	Main file parser.
`protected void`	`readGraphicControlExt()`	Reads Graphics Control Extension values
`protected void`	`readHeader()`	Reads GIF file header information.
`protected void`	`readImage()`	Reads next frame image
`protected void`	`readLSD()`	Reads Logical Screen Descriptor
`protected void`	`readNetscapeExt()`	Reads Netscape extenstion to obtain iteration count
`protected int`	`readShort()`	Reads next 16-bit value, LSB first
`protected void`	`resetFrame()`	Resets frame state for reading next image.
`protected void`	`setPixels()`	Creates new frame image from current data (and previous frames as specified by their disposition codes).
`protected void`	`skip()`	Skips variable length blocks up to and including next zero length block.

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

- Field Detail
  - STATUS_OK
```
public static final int STATUS_OK
```
    File read status: No errors.
    
    See Also:
    
    Constant Field Values
  - STATUS_FORMAT_ERROR
```
public static final int STATUS_FORMAT_ERROR
```
    File read status: Error decoding file (may be partially decoded)
    
    See Also:
    
    Constant Field Values
  - STATUS_OPEN_ERROR
```
public static final int STATUS_OPEN_ERROR
```
    File read status: Unable to open source.
    
    See Also:
    
    Constant Field Values
  - in
```
protected java.io.BufferedInputStream in
```
  - status
```
protected int status
```
  - width
```
protected int width
```
  - height
```
protected int height
```
  - gctFlag
```
protected boolean gctFlag
```
  - gctSize
```
protected int gctSize
```
  - loopCount
```
protected int loopCount
```
  - gct
```
protected int[] gct
```
  - lct
```
protected int[] lct
```
  - act
```
protected int[] act
```
  - bgIndex
```
protected int bgIndex
```
  - bgColor
```
protected int bgColor
```
  - lastBgColor
```
protected int lastBgColor
```
  - pixelAspect
```
protected int pixelAspect
```
  - lctFlag
```
protected boolean lctFlag
```
  - interlace
```
protected boolean interlace
```
  - lctSize
```
protected int lctSize
```
  - ix
```
protected int ix
```
  - iy
```
protected int iy
```
  - iw
```
protected int iw
```
  - ih
```
protected int ih
```
  - lastRect
```
protected java.awt.Rectangle lastRect
```
  - image
```
protected java.awt.image.BufferedImage image
```
  - lastImage
```
protected java.awt.image.BufferedImage lastImage
```
  - block
```
protected byte[] block
```
  - blockSize
```
protected int blockSize
```
  - dispose
```
protected int dispose
```
  - lastDispose
```
protected int lastDispose
```
  - transparency
```
protected boolean transparency
```
  - delay
```
protected int delay
```
  - transIndex
```
protected int transIndex
```
  - MaxStackSize
```
protected static final int MaxStackSize
```
    See Also:
    
    Constant Field Values
  - prefix
```
protected short[] prefix
```
  - suffix
```
protected byte[] suffix
```
  - pixelStack
```
protected byte[] pixelStack
```
  - pixels
```
protected byte[] pixels
```
  - frames
```
protected java.util.ArrayList<org.opensourcephysics.media.gif.GifDecoder.GifFrame> frames
```
  - frameCount
```
protected int frameCount
```
- Constructor Detail
  - GifDecoder
```
public GifDecoder()
```
- Method Detail
  - getDelay
```
public int getDelay(int n)
```
    Gets display duration for specified frame.
    
    Parameters:
    
    n - int index of frame
    
    Returns:
    
    delay in milliseconds
  - getFrameCount
```
public int getFrameCount()
```
    Gets the number of frames read from file.
    
    Returns:
    
    frame count
  - getImage
```
public java.awt.image.BufferedImage getImage()
```
    Gets the first (or only) image read.
    
    Returns:
    
    BufferedImage containing first frame, or null if none.
  - getLoopCount
```
public int getLoopCount()
```
    Gets the "Netscape" iteration count, if any. A count of 0 means repeat indefinitiely.
    
    Returns:
    
    iteration count if one was specified, else 1.
  - setPixels
```
protected void setPixels()
```
    Creates new frame image from current data (and previous frames as specified by their disposition codes).
  - getFrame
```
public java.awt.image.BufferedImage getFrame(int n)
```
    Gets the image contents of frame n.
    
    Parameters:
    
    n - the frame number
    
    Returns:
    
    BufferedImage representation of frame, or null if n is invalid.
  - getFrameSize
```
public java.awt.Dimension getFrameSize()
```
    Gets image size.
    
    Returns:
    
    GIF image dimensions
  - read
```
public int read(java.io.BufferedInputStream input)
```
    Reads GIF image from stream
    
    Parameters:
    
    input - the BufferedInputStream containing GIF file.
    
    Returns:
    
    read status code (0 = no errors)
  - read
```
public int read(java.lang.String name)
```
    Reads GIF file from specified file/URL source (URL assumed if name contains ":/" or "file:")
    
    Parameters:
    
    name - String containing source
    
    Returns:
    
    read status code (0 = no errors)
  - decodeImageData
```
protected void decodeImageData()
```
    Decodes LZW image data into pixel array. Adapted from John Cristy's ImageMagick.
  - err
```
protected boolean err()
```
    Returns true if an error was encountered during reading/decoding
    
    Returns:
    
    true if an error occurred
  - init
```
protected void init()
```
    Initializes or re-initializes reader
  - read
```
protected int read()
```
    Reads a single byte from the input stream.
    
    Returns:
    
    the byte read
  - readBlock
```
protected int readBlock()
```
    Reads next variable length block from input.
    
    Returns:
    
    number of bytes stored in "buffer"
  - readColorTable
```
protected int[] readColorTable(int ncolors)
```
    Reads color table as 256 RGB integer values
    
    Parameters:
    
    ncolors - int number of colors to read
    
    Returns:
    
    int array containing 256 colors (packed ARGB with full alpha)
  - readContents
```
protected void readContents()
```
    Main file parser. Reads GIF content blocks.
  - readGraphicControlExt
```
protected void readGraphicControlExt()
```
    Reads Graphics Control Extension values
  - readHeader
```
protected void readHeader()
```
    Reads GIF file header information.
  - readImage
```
protected void readImage()
```
    Reads next frame image
  - readLSD
```
protected void readLSD()
```
    Reads Logical Screen Descriptor
  - readNetscapeExt
```
protected void readNetscapeExt()
```
    Reads Netscape extenstion to obtain iteration count
  - readShort
```
protected int readShort()
```
    Reads next 16-bit value, LSB first
    
    Returns:
    
    the value read
  - resetFrame
```
protected void resetFrame()
```
    Resets frame state for reading next image.
  - skip
```
protected void skip()
```
    Skips variable length blocks up to and including next zero length block.

Class GifDecoder

Field Summary

Constructor Summary

Method Summary

Methods inherited from class java.lang.Object

Field Detail

STATUS_OK

STATUS_FORMAT_ERROR

STATUS_OPEN_ERROR

in

status

width

height

gctFlag

gctSize

loopCount

gct

lct

act

bgIndex

bgColor

lastBgColor

pixelAspect

lctFlag

interlace

lctSize

ix

iy

iw

ih

lastRect

image

lastImage

block

blockSize

dispose

lastDispose

transparency

delay

transIndex

MaxStackSize

prefix

suffix

pixelStack

pixels

frames

frameCount

Constructor Detail

GifDecoder

Method Detail

getDelay

getFrameCount

getImage

getLoopCount

setPixels

getFrame

getFrameSize

read

read

decodeImageData

err

init

read

readBlock

readColorTable

readContents

readGraphicControlExt

readHeader

readImage

readLSD

readNetscapeExt

readShort

resetFrame

skip