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JPEGDecodeParam encapsulates tables and options necessary to control decoding JPEG datastreams. Parameters are either set explicitly by the application for encoding, or read from the JPEG header for decoding. In the case of decoding abbreviated data streams the application may need to set some/all of the values it's self.
When working with BufferedImages (@see JPEGImageDecoder.decodeBufferedImage), the codec will attempt to generate an appropriate ColorModel for the JPEG COLOR_ID. This is not always possible (example mappings are listed below) . In cases where unsupported conversions are required, or unknown encoded COLOR_ID's are in use, the user must request the data as a Raster and perform the transformations themselves. When decoding into a raster (@see JPEGImageDecoder.decodeRaster) no ColorSpace adjustments are made. Note: The color ids described herein are simply enumerated values that influence data processing by the JPEG codec. JPEG compression is by definition color blind. These values are used as hints when decompressing JPEG data. Of particular interest is the default conversion from YCbCr to sRGB when decoding buffered Images.
Note: because JPEG is mostly color-blind color fidelity can not be garunteed. This will hopefully be rectified in the near future by the wide spread inclusion of ICC-profiles in the JPEG data stream (as a special marker). The following is an example of the conversions that take place. This is only a guide to the types of conversions that are allowed. This list is likely to change in the future so it is strongly recommended that you check for thrown ImageFormatExceptions and check the actual ColorModel associated with the BufferedImage returned rather than make assumtions.
DECODING: JPEG (Encoded) Color ID BufferedImage ColorSpace ======================= ======================== COLOR_ID_UNKNOWN ** Invalid ** COLOR_ID_GRAY CS_GRAY COLOR_ID_RGB CS_sRGB COLOR_ID_YCbCr CS_sRGB COLOR_ID_CMYK ** Invalid ** COLOR_ID_PYCC CS_PYCC COLOR_ID_RGBA CS_sRGB (w/ alpha) COLOR_ID_YCbCrA CS_sRGB (w/ alpha) COLOR_ID_RGBA_INVERTED ** Invalid ** COLOR_ID_YCbCrA_INVERTED ** Invalid ** COLOR_ID_PYCCA CS_PYCC (w/ alpha) COLOR_ID_YCCK ** Invalid **If the user needs better control over conversion, the user must request the data as a Raster and handle the conversion of the image data themselves.
When decoding JFIF files the encoded COLOR_ID will always be one of: COLOR_ID_UNKNOWN, COLOR_ID_GRAY, COLOR_ID_RGB, COLOR_ID_YCbCr, COLOR_ID_CMYK, or COLOR_ID_YCCK
Note that the classes in the com.sun.image.codec.jpeg package are not part of the core Java APIs. They are a part of Sun's JDK and JRE distributions. Although other licensees may choose to distribute these classes, developers cannot depend on their availability in non-Sun implementations. We expect that equivalent functionality will eventually be available in a core API or standard extension.
Field Summary | |
static int |
APP0_MARKER
APP0 marker - JFIF info |
static int |
APP1_MARKER
APP1 marker |
static int |
APP2_MARKER
APP2 marker |
static int |
APP3_MARKER
APP3 marker |
static int |
APP4_MARKER
APP4 marker |
static int |
APP5_MARKER
APP5 marker |
static int |
APP6_MARKER
APP6 marker |
static int |
APP7_MARKER
APP7 marker |
static int |
APP8_MARKER
APP8 marker |
static int |
APP9_MARKER
APP9 marker |
static int |
APPA_MARKER
APPA marker |
static int |
APPB_MARKER
APPB marker |
static int |
APPC_MARKER
APPC marker |
static int |
APPD_MARKER
APPD marker |
static int |
APPE_MARKER
APPE marker - Adobe info |
static int |
APPF_MARKER
APPF marker |
static int |
COLOR_ID_CMYK
CMYK |
static int |
COLOR_ID_GRAY
Monochrome |
static int |
COLOR_ID_PYCC
PhotoYCC |
static int |
COLOR_ID_PYCCA
PhotoYCC-Alpha |
static int |
COLOR_ID_RGB
Red, Green, and Blue |
static int |
COLOR_ID_RGBA
RGB-Alpha |
static int |
COLOR_ID_RGBA_INVERTED
RGB-Alpha with R, G, and B inverted. |
static int |
COLOR_ID_UNKNOWN
Unknown or Undefined Color ID |
static int |
COLOR_ID_YCbCr
YCbCr |
static int |
COLOR_ID_YCbCrA
YCbCr-Alpha |
static int |
COLOR_ID_YCbCrA_INVERTED
YCbCr-Alpha with Y, Cb, and Cr inverted. |
static int |
COLOR_ID_YCCK
YCbCrK |
static int |
COMMENT_MARKER
Adobe marker indicates presence/need for Adobe marker. |
static int |
DENSITY_UNIT_ASPECT_RATIO
The X and Y units simply indicate the aspect ratio of the pixels. |
static int |
DENSITY_UNIT_DOTS_CM
Pixel density is in pixels per centemeter. |
static int |
DENSITY_UNIT_DOTS_INCH
Pixel density is in pixels per inch. |
static int |
NUM_COLOR_ID
Number of color ids defined. |
static int |
NUM_DENSITY_UNIT
The max known value for DENSITY_UNIT |
static int |
NUM_TABLES
Number of allowed Huffman and Quantization Tables |
Method Summary | |
Object |
clone()
|
int |
getACHuffmanComponentMapping(int component)
Get the number of the AC Huffman table that will be used for a particular component. |
JPEGHuffmanTable |
getACHuffmanTable(int tableNum)
Returns the AC Huffman coding table requested or null if not defined |
JPEGHuffmanTable |
getACHuffmanTableForComponent(int component)
Returns the AC Huffman coding table for the requested component. |
int |
getDCHuffmanComponentMapping(int component)
Get the number of the DC Huffman table that will be used for a particular component. |
JPEGHuffmanTable |
getDCHuffmanTable(int tableNum)
Returns the DC Huffman coding table requested or null if not defined |
JPEGHuffmanTable |
getDCHuffmanTableForComponent(int component)
Returns the DC Huffman coding table for the requested component. |
int |
getDensityUnit()
Get the code for pixel size units This value is copied from the APP0 marker. |
int |
getEncodedColorID()
Returns the JPEG Encoded color id. |
int |
getHeight()
Get the image height |
int |
getHorizontalSubsampling(int component)
Return the Horizontal subsampling factor for requested Component. |
boolean |
getMarker(int marker)
Returns true if at least one instance of the marker is present in the Parameter object. |
byte[][] |
getMarkerData(int marker)
Returns a 'byte[][]' associated with the requested marker in the parameter object. |
int |
getNumComponents()
Returns the number of components for the current encoding COLOR_ID. |
JPEGQTable |
getQTable(int tableNum)
Returns the coefficient quantization tables or NULL if not defined. |
int |
getQTableComponentMapping(int component)
Get the number of the quantization table that will be used for a particular component. |
JPEGQTable |
getQTableForComponent(int component)
Returns the Quantization table for the requested component. |
int |
getRestartInterval()
Get the MCUs per restart marker. |
int |
getVerticalSubsampling(int component)
Return the Vertical subsampling factor for requested Component. |
int |
getWidth()
Get the image width |
int |
getXDensity()
Get the horizontal pixel density This value is copied from the APP0 marker. |
int |
getYDensity()
Get the vertical pixel density This value is copied into the APP0 marker. |
boolean |
isImageInfoValid()
Returns true if the image information in the ParamBlock is currently valid. |
boolean |
isTableInfoValid()
Returns true if the tables in the ParamBlock are currently valid. |
Field Detail |
public static final int COLOR_ID_UNKNOWN
public static final int COLOR_ID_GRAY
public static final int COLOR_ID_RGB
public static final int COLOR_ID_YCbCr
public static final int COLOR_ID_CMYK
public static final int COLOR_ID_PYCC
public static final int COLOR_ID_RGBA
public static final int COLOR_ID_YCbCrA
public static final int COLOR_ID_RGBA_INVERTED
public static final int COLOR_ID_YCbCrA_INVERTED
public static final int COLOR_ID_PYCCA
public static final int COLOR_ID_YCCK
public static final int NUM_COLOR_ID
public static final int NUM_TABLES
public static final int DENSITY_UNIT_ASPECT_RATIO
public static final int DENSITY_UNIT_DOTS_INCH
public static final int DENSITY_UNIT_DOTS_CM
public static final int NUM_DENSITY_UNIT
public static final int APP0_MARKER
public static final int APP1_MARKER
public static final int APP2_MARKER
public static final int APP3_MARKER
public static final int APP4_MARKER
public static final int APP5_MARKER
public static final int APP6_MARKER
public static final int APP7_MARKER
public static final int APP8_MARKER
public static final int APP9_MARKER
public static final int APPA_MARKER
public static final int APPB_MARKER
public static final int APPC_MARKER
public static final int APPD_MARKER
public static final int APPE_MARKER
public static final int APPF_MARKER
public static final int COMMENT_MARKER
Method Detail |
public Object clone()
public int getWidth()
public int getHeight()
public int getHorizontalSubsampling(int component)
component
- The component of the encoded image to return
the subsampling factor for.
public int getVerticalSubsampling(int component)
component
- The component of the encoded image to return
the subsampling factor for.
public JPEGQTable getQTable(int tableNum)
tableNum
- the index of the table to be returned.
public JPEGQTable getQTableForComponent(int component)
component
- the image component of interest.
public JPEGHuffmanTable getDCHuffmanTable(int tableNum)
tableNum
- the index of the table to be returned.
public JPEGHuffmanTable getDCHuffmanTableForComponent(int component)
component
- the image component of interest.
public JPEGHuffmanTable getACHuffmanTable(int tableNum)
tableNum
- the index of the table to be returned.
public JPEGHuffmanTable getACHuffmanTableForComponent(int component)
component
- the image component of interest.
public int getDCHuffmanComponentMapping(int component)
component
- The Component of interest.
public int getACHuffmanComponentMapping(int component)
component
- The Component of interest.
public int getQTableComponentMapping(int component)
component
- The Component of interest.
public boolean isImageInfoValid()
public boolean isTableInfoValid()
public boolean getMarker(int marker)
marker
- The marker of interest.public byte[][] getMarkerData(int marker)
marker
- The marker of interest.
public int getEncodedColorID()
public int getNumComponents()
public int getRestartInterval()
public int getDensityUnit()
public int getXDensity()
getDensityUnit()
public int getYDensity()
getDensityUnit()
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