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java.lang.Objectjavax.imageio.IIOParam
javax.imageio.ImageReadParam
javax.imageio.plugins.jpeg.JPEGImageReadParam
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 and JPEGQTable for more information on the default
tables.
JPEGHuffmanTable
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 and JPEGQTable.
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 method of
the reader must be called to change the stream.
setInput
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 inherited from class javax.imageio.ImageReadParam |
canSetSourceRenderSize, destination, destinationBands, minProgressivePass, numProgressivePasses, sourceRenderSize |
| Fields inherited from class javax.imageio.IIOParam |
controller, defaultController, destinationOffset, destinationType, sourceBands, sourceRegion, sourceXSubsampling, sourceYSubsampling, subsamplingXOffset, subsamplingYOffset |
| Constructor Summary | |
JPEGImageReadParam()
Constructs a JPEGImageReadParam. |
|
| Method Summary | |
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 inherited from class java.lang.Object |
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait |
| Constructor Detail |
public JPEGImageReadParam()
JPEGImageReadParam.
| Method Detail |
public boolean areTablesSet()
true if tables are currently set.
true if tables are present.
public void setDecodeTables(JPEGQTable[] qTables,
JPEGHuffmanTable[] DCHuffmanTables,
JPEGHuffmanTable[] ACHuffmanTables)
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.
qTables - an array of quantization table objects.DCHuffmanTables - an array of Huffman table objects.ACHuffmanTables - an array of Huffman table objects.
IllegalArgumentException - if any of the arguments
is null, has more than 4 elements, or if the
numbers of DC and AC tables differ.unsetDecodeTables()public void unsetDecodeTables()
setDecodeTables(javax.imageio.plugins.jpeg.JPEGQTable[], javax.imageio.plugins.jpeg.JPEGHuffmanTable[], javax.imageio.plugins.jpeg.JPEGHuffmanTable[])public JPEGQTable[] getQTables()
setDecodeTables, or
null if tables are not currently set.
JPEGQTable objects, or
null.setDecodeTables(javax.imageio.plugins.jpeg.JPEGQTable[], javax.imageio.plugins.jpeg.JPEGHuffmanTable[], javax.imageio.plugins.jpeg.JPEGHuffmanTable[])public JPEGHuffmanTable[] getDCHuffmanTables()
setDecodeTables, or
null if tables are not currently set.
JPEGHuffmanTable objects, or
null.setDecodeTables(javax.imageio.plugins.jpeg.JPEGQTable[], javax.imageio.plugins.jpeg.JPEGHuffmanTable[], javax.imageio.plugins.jpeg.JPEGHuffmanTable[])public JPEGHuffmanTable[] getACHuffmanTables()
setDecodeTables, or
null if tables are not currently set.
JPEGHuffmanTable objects, or
null.setDecodeTables(javax.imageio.plugins.jpeg.JPEGQTable[], javax.imageio.plugins.jpeg.JPEGHuffmanTable[], javax.imageio.plugins.jpeg.JPEGHuffmanTable[])
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JavaTM 2 Platform Std. Ed. v1.4.2 |
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Copyright 2003 Sun Microsystems, Inc. All rights reserved. Use is subject to license terms. Also see the documentation redistribution policy.