Scanning docs for bitsavers

Paul Berger phb.hfx at
Tue Dec 3 11:59:17 CST 2019

On 2019-12-02 4:57 p.m., Eric Smith via cctalk wrote:
> On Tue, Nov 26, 2019 at 8:51 PM Jay Jaeger via cctalk <cctalk at>
> wrote:
>> When I corresponded with Al Kossow about format several years ago, he
>> indicated that CCITT Group 4 lossless compression was their standard.
> There are newer bilevel encodings that are somewhat more efficient than G4
> (ITU-T T.6), such as JBIG (T.82) and JBIG2 (T.88), but they are not as
> widely supported, and AFAIK JBIG2 is still patent encumbered. As a result,
> G4 is still arguably the best bilevel encoding for general-purpose use. PDF
> has natively supported G4 for ages, though it gained JBIG and JBIG2 support
> in more recent versions.
> Back in 2001, support for G4 encoding in open source software was really
> awful; where it existed at all, it was horribly slow. There was no good
> reason for G4 encoding to be slow, which was part of my motivation in
> writing my own G4 encoder for tumble (an image-to-PDF utility). However, G4
> support is generally much better now.

Is there any way to know what compression was used in a pdf file?

Do you know anything about a compression format JPEG2000?

Would TIFF G4 still be preferable to JPEG2000? It would seem I can 
control the compression used by selecting the pdf compatibility level.


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