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non_com.media.jai.codec
Class TIFFDecodeParam  

java.lang.Object
  non_com.media.jai.codec.TIFFDecodeParam

All Implemented Interfaces:

java.lang.Cloneable, ImageDecodeParam, java.io.Serializable

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public class TIFFDecodeParam

extends java.lang.Object

implements ImageDecodeParam

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.

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Field Summary
private  boolean	convertJPEGYCbCrToRGB
private  boolean	decodePaletteAsShorts
private  java.lang.Long	ifdOffset

 

Constructor 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.
java.lang.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

 

Field Detail

decodePaletteAsShorts

private boolean decodePaletteAsShorts

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ifdOffset

private java.lang.Long ifdOffset

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convertJPEGYCbCrToRGB

private boolean convertJPEGYCbCrToRGB

Constructor Detail

TIFFDecodeParam

public TIFFDecodeParam()

Constructs a default instance of TIFFDecodeParam.

Method Detail

setDecodePaletteAsShorts

public 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.

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setIFDOffset

public void setIFDOffset(long offset)

Sets the offset in the stream from which to read the image. There must be an Image File Directory (IFD) at that position or an error will occur. If 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.

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setJPEGDecompressYCbCrToRGB

public void setJPEGDecompressYCbCrToRGB(boolean convertJPEGYCbCrToRGB)

Sets a flag indicating whether to convert JPEG-compressed YCbCr data to RGB. The default value is true. This flag is ignored if the image data are not JPEG-compressed.

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getDecodePaletteAsShorts

public boolean getDecodePaletteAsShorts()

Returns true if palette entries will be decoded as shorts, resulting in an output image with short datatype.

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getIFDOffset

public java.lang.Long getIFDOffset()

Returns the value set by setIFDOffset() or null if no value has been set.

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getJPEGDecompressYCbCrToRGB

public boolean getJPEGDecompressYCbCrToRGB()

Whether JPEG-compressed YCbCr data will be converted to RGB.

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decode16BitsTo8Bits

public byte decode16BitsTo8Bits(int s)

Returns an unsigned 8 bit value computed by dithering the unsigned 16 bit value. Note that the TIFF specified short datatype is an unsigned value, while Java'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.

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decodeSigned16BitsTo8Bits

public byte decodeSigned16BitsTo8Bits(short s)

Returns an unsigned 8 bit value computed by dithering the signed 16 bit value. This method deals correctly only with values in the 16 bit signed range.

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Home >> All >> non_com >> media >> jai >> [ codec overview ]	PREV CLASS  NEXT CLASS
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