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. @see TIFFDirectory
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