Package org.loboevolution.pdfview.decode

Class DCTDecode

java.lang.Object

org.loboevolution.pdfview.decode.DCTDecode

public class DCTDecode
extends Object

decode a DCT encoded array into a byte array. This class uses Java's built-in JPEG image class to do the decoding.

Author Mike Wessler

Constructor Summary

Constructors

Constructor	Description
DCTDecode()

Method Summary

Modifier and Type	Method	Description
protected static ByteBuffer	decode(PDFObject dict, ByteBuffer buf, PDFObject params)	decode an array of bytes in DCT format.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Details

DCTDecode

public DCTDecode()

Method Details

decode

protected static ByteBuffer decode(PDFObject dict,
 ByteBuffer buf,
 PDFObject params)
                            throws PDFParseException

decode an array of bytes in DCT format.

DCT is the format used by JPEG images, so this class simply loads the DCT-format bytes as an image, then reads the bytes out of the image to create the array. Unfortunately, their most likely use is to get turned BACK into an image, so this isn't terribly efficient... but is is general... don't hit, please.

The DCT-encoded stream may have 1, 3 or 4 samples per pixel, depending on the colorspace of the image. In decoding, we look for the colorspace in the stream object's dictionary to decide how to decode this image. If no colorspace is present, we guess 3 samples per pixel.

Parameters:

dict - the stream dictionary

buf - the DCT-encoded buffer

params - the parameters to the decoder (ignored)

Returns:

the decoded buffer

Throws:

PDFParseException - if any.