public class

JPEGImageWriteParam

extends ImageWriteParam

java.lang.Object
↳	javax.imageio.IIOParam
	↳	javax.imageio.ImageWriteParam
		↳	javax.imageio.plugins.jpeg.JPEGImageWriteParam

Class Overview

This class adds the ability to set JPEG quantization and Huffman tables when using the built-in JPEG writer plug-in, and to request that optimized Huffman tables be computed for an image. An instance of this class will be returned from the getDefaultImageWriteParam methods of the built-in JPEG ImageWriter.

The principal purpose of these additions is to allow the specification of tables to use in encoding abbreviated streams. The built-in JPEG writer will also accept an ordinary ImageWriteParam, in which case the writer will construct the necessary tables internally.

In either case, the quality setting in an ImageWriteParam has the same meaning as for the underlying library: 1.00 means a quantization table of all 1's, 0.75 means the "standard", visually lossless quantization table, and 0.00 means aquantization table of all 255's.

While tables for abbreviated streams are often specified by first writing an 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.

Normally, the tables are specified in the IIOMetadata objects passed in to the writer, and any tables included in these objects are written to the stream. If no tables are specified in the metadata, then an abbreviated stream is written. If no tables are included in the metadata and no tables are specified in a JPEGImageWriteParam, then an abbreviated stream is encoded using the "standard" visually lossless tables. This class is necessary for specifying tables when an abbreviated stream must be written without writing any tables to a stream first. In order to use this class, the metadata object passed into the writer must contain no tables, and no stream metadata must be provided. See JPEGQTable and JPEGHuffmanTable for more information on the default tables.

The default JPEGImageWriteParam returned by the getDefaultWriteParam method of the writer contains no tables. Default tables are included in the default IIOMetadata objects returned by the writer.

If the metadata does contain tables, the tables given in a JPEGImageWriteParam are ignored. Furthermore, once a set of tables has been written, only tables in the metadata can override them for subsequent writes, whether to the same stream or a different one. In order to specify new tables using this class, the reset method of the writer must be called.

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

Summary

[Expand]

Inherited Constants

From class javax.imageio.ImageWriteParam

[Expand]

Inherited Fields

From class javax.imageio.ImageWriteParam

protected boolean	canOffsetTiles	A `boolean` that is `true` if this `ImageWriteParam` allows tiling grid offset parameters to be set.
protected boolean	canWriteCompressed	A `boolean` that is `true` if this writer can write images using compression.
protected boolean	canWriteProgressive	A `boolean` that is `true` if this `ImageWriteParam` allows images to be written as a progressive sequence of increasing quality passes.
protected boolean	canWriteTiles	A `boolean` that is `true` if this `ImageWriteParam` allows tile width and tile height parameters to be set.
protected int	compressionMode	The mode controlling compression settings, which must be set to one of the four `MODE_*` values.
protected float	compressionQuality	A `float` containing the current compression quality setting.
protected String	compressionType	A `String` containing the name of the current compression type, or `null` if none is set.
protected String[]	compressionTypes	An array of `String`s containing the names of the available compression types.
protected Locale	locale	A `Locale` to be used to localize compression type names and quality descriptions, or `null` to use a default `Locale`.
protected Dimension[]	preferredTileSizes	An array of preferred tile size range pairs.
protected int	progressiveMode	The mode controlling progressive encoding, which must be set to one of the four `MODE_*` values, except `MODE_EXPLICIT`.
protected int	tileGridXOffset	The amount by which the tile grid origin should be offset horizontally from the image origin if tiling has been set, or 0 otherwise.
protected int	tileGridYOffset	The amount by which the tile grid origin should be offset vertically from the image origin if tiling has been set, or 0 otherwise.
protected int	tileHeight	The height of each tile if tiling has been set, or 0 otherwise.
protected int	tileWidth	The width of each tile if tiling has been set, or 0 otherwise.
protected int	tilingMode	The mode controlling tiling settings, which Must be set to one of the four `MODE_*` values.
protected boolean	tilingSet	A `boolean` that is `true` if tiling parameters have been specified.

From class javax.imageio.IIOParam

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 `int`s 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.

Public Constructors
	JPEGImageWriteParam(Locale locale) Constructs a `JPEGImageWriteParam`.

Public Methods
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 `setEncodeTables`, or `null` if tables are not currently set.
String[]	getCompressionQualityDescriptions() Returns an array of `String`s that may be used along with `getCompressionQualityValues` as part of a user interface for setting or displaying the compression quality level.
float[]	getCompressionQualityValues() Returns an array of `float`s that may be used along with `getCompressionQualityDescriptions` as part of a user interface for setting or displaying the compression quality level.
JPEGHuffmanTable[]	getDCHuffmanTables() Returns a copy of the array of DC Huffman tables set on the most recent call to `setEncodeTables`, or `null` if tables are not currently set.
boolean	getOptimizeHuffmanTables() Returns the value passed into the most recent call to `setOptimizeHuffmanTables`, or `false` if `setOptimizeHuffmanTables` has never been called.
JPEGQTable[]	getQTables() Returns a copy of the array of quantization tables set on the most recent call to `setEncodeTables`, or `null` if tables are not currently set.
boolean	isCompressionLossless() Returns `false` since the JPEG plug-in only supports lossy compression.
void	setEncodeTables(JPEGQTable[] qTables, JPEGHuffmanTable[] DCHuffmanTables, JPEGHuffmanTable[] ACHuffmanTables) Sets the quantization and Huffman tables to use in encoding abbreviated streams.
void	setOptimizeHuffmanTables(boolean optimize) Tells the writer to generate optimized Huffman tables for the image as part of the writing process.
void	unsetCompression() Removes any previous compression quality setting.
void	unsetEncodeTables() Removes any quantization and Huffman tables that are currently set.

[Expand]

Inherited Methods

From class javax.imageio.ImageWriteParam

boolean	canOffsetTiles() Returns `true` if the writer can perform tiling with non-zero grid offsets while writing.
boolean	canWriteCompressed() Returns `true` if this writer supports compression.
boolean	canWriteProgressive() Returns `true` if the writer can write out images as a series of passes of progressively increasing quality.
boolean	canWriteTiles() Returns `true` if the writer can perform tiling while writing.
float	getBitRate(float quality) Returns a `float` indicating an estimate of the number of bits of output data for each bit of input image data at the given quality level.
int	getCompressionMode() Returns the current compression mode, if compression is supported.
float	getCompressionQuality() Returns the current compression quality setting.
String[]	getCompressionQualityDescriptions() Returns an array of `String`s that may be used along with `getCompressionQualityValues` as part of a user interface for setting or displaying the compression quality level.
float[]	getCompressionQualityValues() Returns an array of `float`s that may be used along with `getCompressionQualityDescriptions` as part of a user interface for setting or displaying the compression quality level.
String	getCompressionType() Returns the currently set compression type, or `null` if none has been set.
String[]	getCompressionTypes() Returns a list of available compression types, as an array or `String`s, or `null` if a compression type may not be chosen using these interfaces.
Locale	getLocale() Returns the currently set `Locale`, or `null` if only a default `Locale` is supported.
String	getLocalizedCompressionTypeName() Returns a localized version of the name of the current compression type, using the `Locale` returned by `getLocale`.
Dimension[]	getPreferredTileSizes() Returns an array of `Dimension`s indicating the legal size ranges for tiles as they will be encoded in the output file or stream.
int	getProgressiveMode() Returns the current mode for writing the stream in a progressive manner.
int	getTileGridXOffset() Returns the horizontal tile grid offset of an image as it will be written to the output stream.
int	getTileGridYOffset() Returns the vertical tile grid offset of an image as it will be written to the output stream.
int	getTileHeight() Returns the height of each tile in an image as it will be written to the output stream.
int	getTileWidth() Returns the width of each tile in an image as it will be written to the output stream.
int	getTilingMode() Returns the current tiling mode, if tiling is supported.
boolean	isCompressionLossless() Returns `true` if the current compression type provides lossless compression.
void	setCompressionMode(int mode) Specifies whether compression is to be performed, and if so how compression parameters are to be determined.
void	setCompressionQuality(float quality) Sets the compression quality to a value between `0` and `1`.
void	setCompressionType(String compressionType) Sets the compression type to one of the values indicated by `getCompressionTypes`.
void	setProgressiveMode(int mode) Specifies that the writer is to write the image out in a progressive mode such that the stream will contain a series of scans of increasing quality.
void	setTiling(int tileWidth, int tileHeight, int tileGridXOffset, int tileGridYOffset) Specifies that the image should be tiled in the output stream.
void	setTilingMode(int mode) Determines whether the image will be tiled in the output stream and, if it will, how the tiling parameters will be determined.
void	unsetCompression() Removes any previous compression type and quality settings.
void	unsetTiling() Removes any previous tile grid parameters specified by calls to `setTiling`.

From class javax.imageio.IIOParam

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 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.

From class java.lang.Object

Object	clone() Creates and returns a copy of this object.
boolean	equals(Object obj) Indicates whether some other object is "equal to" this one.
void	finalize() Called by the garbage collector on an object when garbage collection determines that there are no more references to the object.
final Class<?>	getClass() Returns the runtime class of this `Object`.
int	hashCode() Returns a hash code value for the 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 another thread invokes the `notify()` method or the `notifyAll()` method for this object.
final void	wait(long timeout, int nanos) Causes the current thread to wait until another thread invokes the `notify()` method or the `notifyAll()` method for this object, or some other thread interrupts the current thread, or a certain amount of real time has elapsed.
final void	wait(long timeout) Causes the current thread to wait until either another thread invokes the `notify()` method or the `notifyAll()` method for this object, or a specified amount of time has elapsed.

Public Constructors

public JPEGImageWriteParam (Locale locale)

Constructs a JPEGImageWriteParam. Tiling is not supported. Progressive encoding is supported. The default progressive mode is MODE_DISABLED. A single form of compression, named "JPEG", is supported. The default compression quality is 0.75.

Parameters

locale	a `Locale` to be used by the superclass to localize compression type names and quality descriptions, or `null`.

Public Methods

public boolean areTablesSet ()

Returns true if tables are currently set.

Returns

true if tables are present.

public JPEGHuffmanTable[] getACHuffmanTables ()

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

Returns

an array of JPEGHuffmanTable objects, or null.

public String[] getCompressionQualityDescriptions ()

Returns an array of Strings that may be used along with getCompressionQualityValues as part of a user interface for setting or displaying the compression quality level. The String with index i provides a description of the range of quality levels between getCompressionQualityValues[i] and getCompressionQualityValues[i + 1]. Note that the length of the array returned from getCompressionQualityValues will always be one greater than that returned from getCompressionQualityDescriptions.

As an example, the strings "Good", "Better", and "Best" could be associated with the ranges [0, .33), [.33, .66), and [.66, 1.0]. In this case, getCompressionQualityDescriptions would return { "Good", "Better", "Best" } and getCompressionQualityValues would return { 0.0F, .33F, .66F, 1.0F }.

If no descriptions are available, null is returned. If null is returned from getCompressionQualityValues, this method must also return null.

The descriptions should be localized for the Locale returned by getLocale, if it is non-null.

If there are multiple compression types but none has been set, an IllegalStateException is thrown.

The default implementation checks that compression is supported and that the compression mode is MODE_EXPLICIT. If so, if getCompressionTypes() is null or getCompressionType() is non-null, it returns null.

Returns

an array of Strings containing localized descriptions of the compression quality levels.

public float[] getCompressionQualityValues ()

Returns an array of floats that may be used along with getCompressionQualityDescriptions as part of a user interface for setting or displaying the compression quality level. See getCompressionQualityDescriptions for more information.

If no descriptions are available, null is returned. If null is returned from getCompressionQualityDescriptions, this method must also return null.

If there are multiple compression types but none has been set, an IllegalStateException is thrown.

The default implementation checks that compression is supported and that the compression mode is MODE_EXPLICIT. If so, if getCompressionTypes() is null or getCompressionType() is non-null, it returns null.

Returns

an array of floats indicating the boundaries between the compression quality levels as described by the Strings from getCompressionQualityDescriptions.

public JPEGHuffmanTable[] getDCHuffmanTables ()

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

Returns

an array of JPEGHuffmanTable objects, or null.

public boolean getOptimizeHuffmanTables ()

Returns the value passed into the most recent call to setOptimizeHuffmanTables, or false if setOptimizeHuffmanTables has never been called.

Returns

true if the writer will generate optimized Huffman tables.

public JPEGQTable[] getQTables ()

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

Returns

an array of JPEGQTable objects, or null.

public boolean isCompressionLossless ()

Returns false since the JPEG plug-in only supports lossy compression.

Returns

false.

Throws

IllegalStateException	if the compression mode is not `MODE_EXPLICIT`.

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

Sets the quantization and Huffman tables to use in encoding abbreviated streams. There may be a maximum of 4 tables of each type. These tables are ignored if tables are specified in the metadata. 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 metadata 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` or has more than 4 elements, or if the numbers of DC and AC tables differ.

public void setOptimizeHuffmanTables (boolean optimize)

Tells the writer to generate optimized Huffman tables for the image as part of the writing process. The default is false. If this flag is set to true, it overrides any tables specified in the metadata. Note that this means that any image written with this flag set to true will always contain Huffman tables.

Parameters

optimize	A boolean indicating whether to generate optimized Huffman tables when writing.

public void unsetCompression ()

Removes any previous compression quality setting.

The default implementation resets the compression quality to 0.75F.

Throws

IllegalStateException	if the compression mode is not `MODE_EXPLICIT`.

public void unsetEncodeTables ()

Removes any quantization and Huffman tables that are currently set.

Classes

JPEGImageWriteParam

Class Overview

Summary

Public Constructors

public JPEGImageWriteParam (Locale locale)

Parameters

Public Methods

public boolean areTablesSet ()

Returns

public JPEGHuffmanTable[] getACHuffmanTables ()

Returns

See Also

public String[] getCompressionQualityDescriptions ()

Returns

public float[] getCompressionQualityValues ()

Returns

public JPEGHuffmanTable[] getDCHuffmanTables ()

Returns

See Also

public boolean getOptimizeHuffmanTables ()

Returns

See Also

public JPEGQTable[] getQTables ()

Returns

See Also

public boolean isCompressionLossless ()

Returns

Throws

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

Parameters

Throws

See Also

public void setOptimizeHuffmanTables (boolean optimize)

Parameters

See Also

public void unsetCompression ()

Throws

public void unsetEncodeTables ()

See Also