com.bumptech.glide.gifdecoder

Class GifDecoder

java.lang.Object

com.bumptech.glide.gifdecoder.GifDecoder

public class GifDecoder
extends Object

Reads frame data from a GIF image source and decodes it into individual frames for animation purposes. Image data can be read from either and InputStream source or a byte[]. This class is optimized for running animations with the frames, there are no methods to get individual frame images, only to decode the next frame in the animation sequence. Instead, it lowers its memory footprint by only housing the minimum data necessary to decode the next frame in the animation sequence. The animation must be manually moved forward using advance() before requesting the next frame. This method must also be called before you request the first frame or an error will occur. Implementation adapted from sample code published in Lyons. (2004). Java for Programmers, republished under the MIT Open Source License

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
static interface	GifDecoder.BitmapProvider An interface that can be used to provide reused Bitmaps to avoid GCs from constantly allocating Bitmaps for every frame.

Field Summary

Fields

Modifier and Type	Field and Description
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.
static int	STATUS_PARTIAL_DECODE Unable to fully decode the current frame.
static int	TOTAL_ITERATION_COUNT_FOREVER The total iteration count which means repeat forever.

Constructor Summary

Constructors

Constructor and Description
GifDecoder(GifDecoder.BitmapProvider provider)

Method Summary

Methods

Modifier and Type	Method and Description
void	advance() Move the animation frame counter forward.
void	clear()
int	getCurrentFrameIndex() Gets the current index of the animation frame, or -1 if animation hasn't not yet started.
byte[]	getData()
int	getDelay(int n) Gets display duration for specified frame.
int	getFrameCount() Gets the number of frames read from file.
int	getHeight()
int	getLoopCount() Deprecated. Use getNetscapeLoopCount() instead. This method cannot distinguish whether the loop count is 1 or doesn't exist.
int	getNetscapeLoopCount() Gets the "Netscape" loop count, if any.
int	getNextDelay() Gets display duration for the upcoming frame in ms.
Bitmap	getNextFrame() Get the next frame in the animation sequence.
int	getStatus() Returns the current status of the decoder.
int	getTotalIterationCount() Gets the total count which represents how many times the animation sequence should be displayed.
int	getWidth()
int	read(byte[] data) Reads GIF image from byte array.
int	read(InputStream is, int contentLength) Reads GIF image from stream.
void	resetFrameIndex()
void	setData(GifHeader header, byte[] data)

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

STATUS_PARTIAL_DECODE

public static final int STATUS_PARTIAL_DECODE

Unable to fully decode the current frame.

See Also:

Constant Field Values

TOTAL_ITERATION_COUNT_FOREVER

public static final int TOTAL_ITERATION_COUNT_FOREVER

The total iteration count which means repeat forever.

See Also:

Constant Field Values

Constructor Detail

GifDecoder

public GifDecoder(GifDecoder.BitmapProvider provider)

Method Detail

getWidth

public int getWidth()

getHeight

public int getHeight()

getData

public byte[] getData()

getStatus

public int getStatus()

Returns the current status of the decoder.

Status will update per frame to allow the caller to tell whether or not the current frame was decoded successfully and/or completely. Format and open failures persist across frames.

advance

public void advance()

Move the animation frame counter forward.

getDelay

public int getDelay(int n)

Gets display duration for specified frame.

Parameters:

n - int index of frame.

Returns:

delay in milliseconds.

getNextDelay

public int getNextDelay()

Gets display duration for the upcoming frame in ms.

getFrameCount

public int getFrameCount()

Gets the number of frames read from file.

Returns:

frame count.

getCurrentFrameIndex

public int getCurrentFrameIndex()

Gets the current index of the animation frame, or -1 if animation hasn't not yet started.

Returns:

frame index.

resetFrameIndex

public void resetFrameIndex()

getLoopCount

@Deprecated
public int getLoopCount()

Deprecated. Use getNetscapeLoopCount() instead. This method cannot distinguish whether the loop count is 1 or doesn't exist.

Gets the "Netscape" loop count, if any. A count of 0 means repeat indefinitely.

Returns:

loop count if one was specified, else 1.

getNetscapeLoopCount

public int getNetscapeLoopCount()

Gets the "Netscape" loop count, if any. A count of 0 (GifHeader.NETSCAPE_LOOP_COUNT_FOREVER) means repeat indefinitely. It must not be a negative value.
Use getTotalIterationCount() to know how many times the animation sequence should be displayed.

Returns:

loop count if one was specified, else -1 (GifHeader.NETSCAPE_LOOP_COUNT_DOES_NOT_EXIST).

getTotalIterationCount

public int getTotalIterationCount()

Gets the total count which represents how many times the animation sequence should be displayed. A count of 0 (TOTAL_ITERATION_COUNT_FOREVER) means repeat indefinitely. It must not be a negative value.

The total count is calculated as follows by using getNetscapeLoopCount(). This behavior is the same as most web browsers.

getNetscapeLoopCount()	The total count
GifHeader.NETSCAPE_LOOP_COUNT_FOREVER	TOTAL_ITERATION_COUNT_FOREVER
GifHeader.NETSCAPE_LOOP_COUNT_DOES_NOT_EXIST	1
n (n > 0)	n +1

Returns:

total iteration count calculated from "Netscape" loop count.

See Also:

Discussion about the iteration count of animated GIFs (Chromium Issue 592735)

getNextFrame

public Bitmap getNextFrame()

Get the next frame in the animation sequence.

Returns:

Bitmap representation of frame.

read

public int read(InputStream is,
       int contentLength)

Reads GIF image from stream.

Parameters:

is - containing GIF file.

Returns:

read status code (0 = no errors).

clear

public void clear()

setData

public void setData(GifHeader header,
           byte[] data)

read

public int read(byte[] data)

Reads GIF image from byte array.

Parameters:

data - containing GIF file.

Returns:

read status code (0 = no errors).