Class JPEGImageReadParam

java.lang.Object

javax.imageio.IIOParam

javax.imageio.ImageReadParam

javax.imageio.plugins.jpeg.JPEGImageReadParam

public class JPEGImageReadParam
extends ImageReadParam

This class adds the ability to set JPEG quantization and Huffman tables when using the built-in JPEG reader plug-in. An instance of this class will be returned from the getDefaultImageReadParam methods of the built-in JPEG ImageReader.

The sole purpose of these additions is to allow the specification of tables for use in decoding abbreviated streams. The built-in JPEG reader will also accept an ordinary ImageReadParam, which is sufficient for decoding non-abbreviated streams.

While tables for abbreviated streams are often obtained by first reading another abbreviated stream containing only the tables, in some applications the tables are fixed ahead of time. This class allows the tables to be specified directly from client code. If no tables are specified either in the stream or in a JPEGImageReadParam, then the stream is presumed to use the "standard" visually lossless tables. See JPEGQTable and JPEGHuffmanTable for more information on the default tables.

The default JPEGImageReadParam returned by the getDefaultReadParam method of the builtin JPEG reader contains no tables. Default tables may be obtained from the table classes JPEGQTable and JPEGHuffmanTable.

If a stream does contain tables, the tables given in a JPEGImageReadParam are ignored. Furthermore, if the first image in a stream does contain tables and subsequent ones do not, then the tables given in the first image are used for all the abbreviated images. Once tables have been read from a stream, they can be overridden only by tables subsequently read from the same stream. In order to specify new tables, the setInput method of the reader must be called to change the stream.

Note that this class does not provide a means for obtaining the tables found in a stream. These may be extracted from a stream by consulting the IIOMetadata object returned by the reader.

For more information about the operation of the built-in JPEG plug-ins, see the JPEG metadata format specification and usage notes.

Field Summary

Fields declared in class ImageReadParam

canSetSourceRenderSize, destination, destinationBands, minProgressivePass, numProgressivePasses, sourceRenderSize

Modifier and Type	Field	Description
protected boolean	canSetSourceRenderSize	true if this ImageReadParam allows the source rendering dimensions to be set.
protected BufferedImage	destination	The current destination BufferedImage, or null if none has been set.
protected int[]	destinationBands	The set of destination bands to be used, as an array of ints.
protected int	minProgressivePass	The minimum index of a progressive pass to read from the source.
protected int	numProgressivePasses	The maximum number of progressive passes to read from the source.
protected Dimension	sourceRenderSize	The desired rendering width and height of the source, if canSetSourceRenderSize is true, or null.

Fields declared in class IIOParam

controller, defaultController, destinationOffset, destinationType, sourceBands, sourceRegion, sourceXSubsampling, sourceYSubsampling, subsamplingXOffset, subsamplingYOffset

Modifier and Type	Field	Description
protected IIOParamController	controller	The IIOParamController that will be used to provide settings for this IIOParam object when the activateController method is called.
protected IIOParamController	defaultController	The default IIOParamController that will be used to provide settings for this IIOParam object when the activateController method is called.
protected Point	destinationOffset	The offset in the destination where the upper-left decoded pixel should be placed.
protected ImageTypeSpecifier	destinationType	An ImageTypeSpecifier to be used to generate a destination image when reading, or to set the output color type when writing.
protected int[]	sourceBands	An array of ints indicating which source bands will be used, or null.
protected Rectangle	sourceRegion	The source region, on null if none is set.
protected int	sourceXSubsampling	The decimation subsampling to be applied in the horizontal direction.
protected int	sourceYSubsampling	The decimation subsampling to be applied in the vertical direction.
protected int	subsamplingXOffset	A horizontal offset to be applied to the subsampling grid before subsampling.
protected int	subsamplingYOffset	A vertical offset to be applied to the subsampling grid before subsampling.

Constructor Summary

Constructors

Constructor	Description
JPEGImageReadParam()	Constructs a JPEGImageReadParam.

Method Summary

Modifier and Type	Method	Description
boolean	areTablesSet()	Returns true if tables are currently set.
JPEGHuffmanTable[]	getACHuffmanTables()	Returns a copy of the array of AC Huffman tables set on the most recent call to setDecodeTables, or null if tables are not currently set.
JPEGHuffmanTable[]	getDCHuffmanTables()	Returns a copy of the array of DC Huffman tables set on the most recent call to setDecodeTables, or null if tables are not currently set.
JPEGQTable[]	getQTables()	Returns a copy of the array of quantization tables set on the most recent call to setDecodeTables, or null if tables are not currently set.
void	setDecodeTables(JPEGQTable[] qTables, JPEGHuffmanTable[] DCHuffmanTables, JPEGHuffmanTable[] ACHuffmanTables)	Sets the quantization and Huffman tables to use in decoding abbreviated streams.
void	unsetDecodeTables()	Removes any quantization and Huffman tables that are currently set.

Methods declared in class ImageReadParam

canSetSourceRenderSize, getDestination, getDestinationBands, getSourceMaxProgressivePass, getSourceMinProgressivePass, getSourceNumProgressivePasses, getSourceRenderSize, setDestination, setDestinationBands, setSourceProgressivePasses, setSourceRenderSize

Modifier and Type	Method	Description
boolean	canSetSourceRenderSize()	Returns true if this reader allows the source image to be rendered at an arbitrary size as part of the decoding process, by means of the setSourceRenderSize method.
BufferedImage	getDestination()	Returns the BufferedImage currently set by the setDestination method, or null if none is set.
int[]	getDestinationBands()	Returns the set of band indices where data will be placed.
int	getSourceMaxProgressivePass()	If getSourceNumProgressivePasses is equal to Integer.MAX_VALUE, returns Integer.MAX_VALUE.
int	getSourceMinProgressivePass()	Returns the index of the first progressive pass that will be decoded.
int	getSourceNumProgressivePasses()	Returns the number of the progressive passes that will be decoded.
Dimension	getSourceRenderSize()	Returns the width and height of the source image as it will be rendered during decoding, if they have been set via the setSourceRenderSize method.
void	setDestination(BufferedImage destination)	Supplies a BufferedImage to be used as the destination for decoded pixel data.
void	setDestinationBands(int[] destinationBands)	Sets the indices of the destination bands where data will be placed.
void	setSourceProgressivePasses(int minPass, int numPasses)	Sets the range of progressive passes that will be decoded.
void	setSourceRenderSize(Dimension size)	If the image is able to be rendered at an arbitrary size, sets the source width and height to the supplied values.

Methods declared in class IIOParam

activateController, getController, getDefaultController, getDestinationOffset, getDestinationType, getSourceBands, getSourceRegion, getSourceXSubsampling, getSourceYSubsampling, getSubsamplingXOffset, getSubsamplingYOffset, hasController, setController, setDestinationOffset, setDestinationType, setSourceBands, setSourceRegion, setSourceSubsampling

Modifier and Type	Method	Description
boolean	activateController()	Activates the installed IIOParamController for this IIOParam object and returns the resulting value.
IIOParamController	getController()	Returns whatever IIOParamController is currently installed.
IIOParamController	getDefaultController()	Returns the default IIOParamController, if there is one, regardless of the currently installed controller.
Point	getDestinationOffset()	Returns the offset in the destination image at which pixels are to be placed.
ImageTypeSpecifier	getDestinationType()	Returns the type of image to be returned by the read, if one was set by a call to setDestination(ImageTypeSpecifier), as an ImageTypeSpecifier.
int[]	getSourceBands()	Returns the set of source bands to be used.
Rectangle	getSourceRegion()	Returns the source region to be used.
int	getSourceXSubsampling()	Returns the number of source columns to advance for each pixel.
int	getSourceYSubsampling()	Returns the number of rows to advance for each pixel.
int	getSubsamplingXOffset()	Returns the horizontal offset of the subsampling grid.
int	getSubsamplingYOffset()	Returns the vertical offset of the subsampling grid.
boolean	hasController()	Returns true if there is a controller installed for this IIOParam object.
void	setController(IIOParamController controller)	Sets the IIOParamController to be used to provide settings for this IIOParam object when the activateController method is called, overriding any default controller.
void	setDestinationOffset(Point destinationOffset)	Specifies the offset in the destination image at which future decoded pixels are to be placed, when reading, or where a region will be written, when writing.
void	setDestinationType(ImageTypeSpecifier destinationType)	Sets the desired image type for the destination image, using an ImageTypeSpecifier.
void	setSourceBands(int[] sourceBands)	Sets the indices of the source bands to be used.
void	setSourceRegion(Rectangle sourceRegion)	Sets the source region of interest.
void	setSourceSubsampling(int sourceXSubsampling, int sourceYSubsampling, int subsamplingXOffset, int subsamplingYOffset)	Specifies a decimation subsampling to apply on I/O.

Methods declared in class Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Modifier and Type	Method	Description
protected Object	clone()	Creates and returns a copy of this object.
boolean	equals(Object obj)	Indicates whether some other object is "equal to" this one.
protected void	finalize()	Deprecated, for removal: This API element is subject to removal in a future version. Finalization is deprecated and subject to removal in a future release.
final Class<?>	getClass()	Returns the runtime class of this Object.
int	hashCode()	Returns a hash code value for this object.
final void	notify()	Wakes up a single thread that is waiting on this object's monitor.
final void	notifyAll()	Wakes up all threads that are waiting on this object's monitor.
String	toString()	Returns a string representation of the object.
final void	wait()	Causes the current thread to wait until it is awakened, typically by being notified or interrupted.
final void	wait(long timeoutMillis)	Causes the current thread to wait until it is awakened, typically by being notified or interrupted, or until a certain amount of real time has elapsed.
final void	wait(long timeoutMillis, int nanos)	Causes the current thread to wait until it is awakened, typically by being notified or interrupted, or until a certain amount of real time has elapsed.

Constructor Details

JPEGImageReadParam

public JPEGImageReadParam()

Constructs a JPEGImageReadParam.

Method Details

areTablesSet

public boolean areTablesSet()

Returns true if tables are currently set.

Returns:

true if tables are present.

setDecodeTables

public void setDecodeTables(JPEGQTable[] qTables,
 JPEGHuffmanTable[] DCHuffmanTables,
 JPEGHuffmanTable[] ACHuffmanTables)

Sets the quantization and Huffman tables to use in decoding abbreviated streams. There may be a maximum of 4 tables of each type. These tables are ignored once tables are encountered in the stream. All arguments must be non-null. The two arrays of Huffman tables must have the same number of elements. The table specifiers in the frame and scan headers in the stream are assumed to be equivalent to indices into these arrays. The argument arrays are copied by this method.

Parameters:

qTables - an array of quantization table objects.

DCHuffmanTables - an array of Huffman table objects.

ACHuffmanTables - an array of Huffman table objects.

Throws:

IllegalArgumentException - if any of the arguments is null, has more than 4 elements, or if the numbers of DC and AC tables differ.

See Also:

• unsetDecodeTables()

unsetDecodeTables

public void unsetDecodeTables()

Removes any quantization and Huffman tables that are currently set.

See Also:

• setDecodeTables(JPEGQTable[], JPEGHuffmanTable[], JPEGHuffmanTable[])

getQTables

public JPEGQTable[] getQTables()

Returns a copy of the array of quantization tables set on the most recent call to setDecodeTables, or null if tables are not currently set.

Returns:

an array of JPEGQTable objects, or null.

See Also:

• setDecodeTables(JPEGQTable[], JPEGHuffmanTable[], JPEGHuffmanTable[])

getDCHuffmanTables

public JPEGHuffmanTable[] getDCHuffmanTables()

Returns a copy of the array of DC Huffman tables set on the most recent call to setDecodeTables, or null if tables are not currently set.

Returns:

an array of JPEGHuffmanTable objects, or null.

See Also:

• setDecodeTables(JPEGQTable[], JPEGHuffmanTable[], JPEGHuffmanTable[])

getACHuffmanTables

public JPEGHuffmanTable[] getACHuffmanTables()

Returns a copy of the array of AC Huffman tables set on the most recent call to setDecodeTables, or null if tables are not currently set.

Returns:

an array of JPEGHuffmanTable objects, or null.

See Also:

• setDecodeTables(JPEGQTable[], JPEGHuffmanTable[], JPEGHuffmanTable[])