Here I come for such an old question. I asked this question before, but in fact, it was not solved, it was just I gave up last time.

To prevent from getting stupid or duplicate answers. I need to explain in advance.

JBIG2 COMPRESSED IMAGE AND IN PDF. not only “JBIG2 image”(without PDF container), not only “convert image to PDF”, not other compression type.

JBIG2 compression can only be used for binary images, in other words, the images contain only two colors, white and black, no gray, no other colorful.

PDF is the only format that support JBIG2 and often used and easily to use.

Software “ImageMagick” and "GraphicsMagick" do not and will not support it.

The software “jbig2enc” in github is buggy to me, no confidence or patience to solve it. The software “image-to-jbig2-pdf” in github is compiled for Microsoft Winodws and too old for Linux.

JBIG2 has lossy way and lossless way, but I want to use lossless only, do not worry the damage to images for me.

For binary image, JBIG2 compression can be better than png, lossless webp, and group4 compression. No need to suggest any other compression method.

Relying on online Internet tool is not a good idea for batch process.

Interesting. I never tried this encoding. I found jbig2enc for Ubuntu - a repo here:

https://launchpad.net/~alex-p/+archive/ubuntu/jbig2enc

Also, it's a snap version:

https://snapcraft.io/install/jbig2enc/ubuntu

It is old software, but looks like it's still maintained. In this situation, I guess the snap is not such a bad idea because of dependencies. So I installed it and gave it a try.

Not so very well documented, but I made a PDF like this:

The first command created 2 files, output.000 and output.sym. The second command is a python script creates a pdf of the 2 files.

The result was a very tiny PDF (2.6kb) with a black and white version of my picture (1.6mb - but 32bits RGBA).

This worked well on KUbuntu 22.04, but I think the snap should work on most distros. Just running "jbig2enc" shows some options, but I have to admit I really don't understand them.

Oh my Marx. I do not like Ubuntu, not using it, and my distribution does not support snapd.

Maybe I should keep waiting for another answer.

I support the opinion that quality programming makes life much easier

Yeah. But I am so sad that capitalism make programmers work much more separately. So many GNU/Linux distribution (hard to test and choose and be accustomed to for newbies and especially for non-English speaker), so many different softwares do duplicate work, so hard for a single software to run in different operating systems......