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java.lang.Object | +--com.sun.media.jai.codec.TIFFDecodeParam
An instance of ImageDecodeParam
for decoding images in
the TIFF format.
To determine the number of images present in a TIFF file, use
the getNumPages()
method on the
ImageDecoder
object that will be used to perform the
decoding. The desired page number may be passed as an argument to
the ImageDecoder.decodeAsRaster)()
or
decodeAsRenderedImage()
methods.
For TIFF Palette color images, the colorMap always has entries
of short data type, the color Black being represented by 0,0,0 and
White by 65536,65536,65536. In order to display these images, the
default behavior is to dither the short values down to 8 bits.
The dithering is done by calling the decode16BitsTo8Bits
method for each short value that needs to be dithered. The method has
the following implementation:
byte b;
short s;
s = s & 0xffff;
b = (byte)((s >> 8) & 0xff);
If a different algorithm is to be used for the dithering, this class
should be subclassed and an appropriate implementation should be
provided for the decode16BitsTo8Bits
method in the subclass.
If the palette contains image data that is signed short, as specified
by the SampleFormat tag, the dithering is done by calling
decodeSigned16BitsTo8Bits
instead. The method has the
following implementation:
byte b;
short s;
b = (byte)((s + Short.MIN_VALUE) >> 8);
In order to use a different algorithm for the dithering, this class
should be subclassed and the method overridden.
If it is desired that the Palette be decoded such that the output
image is of short data type and no dithering is performed, the
setDecodePaletteAsShorts
method should be used.
This class is not a committed part of the JAI API. It may be removed or changed in future releases of JAI.
TIFFDirectory
, Serialized FormConstructor Summary | |
TIFFDecodeParam()
Constructs a default instance of TIFFDecodeParam . |
Method Summary | |
byte |
decode16BitsTo8Bits(int s)
Returns an unsigned 8 bit value computed by dithering the unsigned 16 bit value. |
byte |
decodeSigned16BitsTo8Bits(short s)
Returns an unsigned 8 bit value computed by dithering the signed 16 bit value. |
boolean |
getDecodePaletteAsShorts()
Returns true if palette entries will be decoded as
shorts, resulting in an output image with short datatype. |
Long |
getIFDOffset()
Returns the value set by setIFDOffset() or
null if no value has been set. |
boolean |
getJPEGDecompressYCbCrToRGB()
Whether JPEG-compressed YCbCr data will be converted to RGB. |
void |
setDecodePaletteAsShorts(boolean decodePaletteAsShorts)
If set, the entries in the palette will be decoded as shorts and no short to byte lookup will be applied to them. |
void |
setIFDOffset(long offset)
Sets the offset in the stream from which to read the image. |
void |
setJPEGDecompressYCbCrToRGB(boolean convertJPEGYCbCrToRGB)
Sets a flag indicating whether to convert JPEG-compressed YCbCr data to RGB. |
Methods inherited from class java.lang.Object |
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait |
Constructor Detail |
public TIFFDecodeParam()
TIFFDecodeParam
.Method Detail |
public void setDecodePaletteAsShorts(boolean decodePaletteAsShorts)
public boolean getDecodePaletteAsShorts()
true
if palette entries will be decoded as
shorts, resulting in an output image with short datatype.public byte decode16BitsTo8Bits(int s)
short
datatype is a
signed value. Therefore the Java short
datatype cannot
be used to store the TIFF specified short value. A Java
int
is used as input instead to this method. The method
deals correctly only with 16 bit unsigned values.public byte decodeSigned16BitsTo8Bits(short s)
public void setIFDOffset(long offset)
setIFDOffset()
is never invoked then
the decoder will assume that the TIFF stream is at the beginning of
the 8-byte image header. If the directory offset is set and a page
number is supplied to the TIFF ImageDecoder
then the
page will be the zero-relative index of the IFD in linked list of
IFDs beginning at the specified offset with a page of zero indicating
the directory at that offset.public Long getIFDOffset()
setIFDOffset()
or
null
if no value has been set.public void setJPEGDecompressYCbCrToRGB(boolean convertJPEGYCbCrToRGB)
true
. This flag is
ignored if the image data are not JPEG-compressed.public boolean getJPEGDecompressYCbCrToRGB()
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