Question: Does bitonal compression of scanned documents to JBIG2 format makes sense on its own or should such conversion be done as part of a general conversion to PDF format?
Answer: JBIG2 is a new ITU-approved, international standard for compression of scanned black and white files. The effectiveness of JBIG2 compression versus the previous ITU TIFF G4 standard is very much dependent on the JBIG2 compression software used. The quality of the scanned document is also a funcion of the JBIG2 software used since the decompression specs for JBIG2 are open but the individual JBIG2 compression algorithms used are proprietary.
Using the right JBIG2 compression software can results in compression rates where the JBIG2 files are 5x-10x smalller than TIFF G4 and G4 PDF, with No Loss of image quality.
Although JBIG2 is an ITU approved format, it is still very new to the industry. The assumption that a typical client or system user has a pre-installed JBIG2 viewer is probably false. The advantage of using JBIG2-compressed PDF as the document format is several fold. First, PDF fully supports JBIG2 so that the compression advantages of JBIG2 can be fully utilized within the PDF specs. Second, PDF Reader 5.0 and up can handle JBIG2-compressed files, so that your user base most likely has a JBIG2 PDF Reader pre-installed on their computer. Third, adding OCR searchability to your JBIG2-compressed file is very easy within the PDF specs using a hidden text layer. And finally, for multipage files that need to be web-hosted and viewed remotely, JBIG2 files that are made to fit the PDF specs (i.e., given a PDF wrapper) can take full advantage of the web-optimization feature supported by PDF and Adobe Reader, which means that large multipage files will open and display quickly on the Web.
So, in short, there are serious advantages in converting scanned documents into JBIG2 format. But having decided to convert a database to JBIG2, there are additional features available and more file control when the files are converted to JBIG2-compressed PDF format.
