JBIG2-Compressed PDF Documents
The Adobe PDF document format has, until the release of the PDF 1.4 specifications, supported the standard compression/decompression filters: LZWDecode, FlateDecode, RunLengthDecode, CCITTFaxDecode, and DCTDecode (JPEG-based). These decoding filters allow the PDF data streams to be compressed when the PDF file is written and then decoded by the Adobe PDF Reader. With the inclusion of the JBIG2Decode filter in the PDF specifications in 2001 (see the PDF Reference, 3rd Edition, Version 1.4), scanned documents can now be encoded using the new ITU-approved JBIG2 format and, at the same time, be fully PDF-compliant.
JBIG and PDF Combined
When a new format is introduced, like JBIG2, JPEG2000, or MPEG4, there is usually a considerable time delay until supporting viewers/players and other editing software is available to handle documents in this new format. One advantage to PDF wrapping a new format like JBIG2 is that readability is essentially guaranteed, assuming a more recent version of Adobe Reader (5.05 or higher) has been installed on the client machine. In fact, most companies currently using JBIG2 for their document compression are using PDFwrapped JBIG2, not native JBIG2. For a slight increase in file size, a JBIG2 document can be wrapped in a PDF, thereby enabling the document to access a range of features supported in PDF that are not available in native JBIG2.