public class JPEGImageWriteParam extends ImageWriteParam
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.
canOffsetTiles, canWriteCompressed, canWriteProgressive, canWriteTiles, compressionMode, compressionQuality, compressionType, compressionTypes, locale, MODE_COPY_FROM_METADATA, MODE_DEFAULT, MODE_DISABLED, MODE_EXPLICIT, preferredTileSizes, progressiveMode, tileGridXOffset, tileGridYOffset, tileHeight, tileWidth, tilingMode, tilingSet
controller, defaultController, destinationOffset, destinationType, sourceBands, sourceRegion, sourceXSubsampling, sourceYSubsampling, subsamplingXOffset, subsamplingYOffset
| Constructor | Description |
|---|---|
JPEGImageWriteParam |
Constructs a JPEGImageWriteParam. |
| 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 setEncodeTables, 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 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 |
Sets the quantization and Huffman tables to use in encoding abbreviated streams. |
void |
setOptimizeHuffmanTables |
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. |
){kind=link}
canOffsetTiles, canWriteCompressed, canWriteProgressive, canWriteTiles, getBitRate, getCompressionMode, getCompressionQuality, getCompressionQualityDescriptions, getCompressionQualityValues, getCompressionType, getCompressionTypes, getLocale, getLocalizedCompressionTypeName, getPreferredTileSizes, getProgressiveMode, getTileGridXOffset, getTileGridYOffset, getTileHeight, getTileWidth, getTilingMode, setCompressionMode, setCompressionQuality, setCompressionType, setProgressiveMode, setTiling, setTilingMode, unsetTiling
activateController, getController, getDefaultController, getDestinationOffset, getDestinationType, getSourceBands, getSourceRegion, getSourceXSubsampling, getSourceYSubsampling, getSubsamplingXOffset, getSubsamplingYOffset, hasController, setController, setDestinationOffset, setDestinationType, setSourceBands, setSourceRegion, setSourceSubsampling
public JPEGImageWriteParam(Locale locale)
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.locale - a Locale to be used by the superclass to localize compression type names and quality descriptions, or null.public void unsetCompression()
The default implementation resets the compression quality to 0.75F.
unsetCompression in class ImageWriteParam
IllegalStateException - if the compression mode is not MODE_EXPLICIT.public boolean isCompressionLossless()
false since the JPEG plug-in only supports lossy compression.isCompressionLossless in class ImageWriteParam
false.IllegalStateException - if the compression mode is not MODE_EXPLICIT.public boolean areTablesSet()
true if tables are currently set.true if tables are present.public void setEncodeTables(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 metadata 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 or has more than 4 elements, or if the numbers of DC and AC tables differ.public void unsetEncodeTables()
public JPEGQTable[] getQTables()
setEncodeTables, or null if tables are not currently set.JPEGQTable objects, or null.public JPEGHuffmanTable[] getDCHuffmanTables()
setEncodeTables, or null if tables are not currently set.JPEGHuffmanTable objects, or null.public JPEGHuffmanTable[] getACHuffmanTables()
setEncodeTables, or null if tables are not currently set.JPEGHuffmanTable objects, or null.public void setOptimizeHuffmanTables(boolean optimize)
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.optimize - A boolean indicating whether to generate optimized Huffman tables when writing.public boolean getOptimizeHuffmanTables()
setOptimizeHuffmanTables, or false if setOptimizeHuffmanTables has never been called.true if the writer will generate optimized Huffman tables.
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