Binary Raster Support (JBIG/JBG/JBIG2)

[ReedGraff]

Would love to see JBIG/JBG/JBIG2 implemented as supported files. They are relatively simple lossless raster formats (https://en.wikipedia.org/wiki/JBIG), seems like a fun challenge.

There is already an opensource C library, made by a Cambridge Prof, that supports this as well (https://www.cl.cam.ac.uk/~mgk25/jbigkit/).
Here is the patent information (http://www.iso.ch/iso/en/CatalogueDetailPage.CatalogueDetail?CSNUMBER=19498&ICS1=35&ICS2=40&ICS3=).

[radarhere]

seems like a fun challenge.

If you're interested in creating a pull request, feel free to do so.

Here is the patent information

Looking at https://en.wikipedia.org/wiki/JBIG, I see

Doubts about patent licence requirements for JBIG1 implementations by IBM, Mitsu­bishi and AT&T prevented the codec from being widely implemented in open-source software.[2] For example, as of 2012, none of the commonly used web browsers supported it.

If you think that the patents are no longer a concern, please elaborate.

If nothing else, that Wikipedia paragraph makes it sound like this is a more obscure format. Why do you feel it should be supported by Pillow?

Do you have sample image that can be added to our test suite and distributed under our license?

[ReedGraff]

Well, I figure the more supported formats the merrier, ImageMagick supports it as well (https://imagemagick.org/script/formats.php#:~:text=Joint%20Bi%2Dlevel%20Image%20experts%20Group%20file%20interchange%20format), and it would be useful to me and I imagine others.

I can get some images etc...

I can start working on a python port, do y'all prefer a DLL / SO port or a fully pythonic port?...

[radarhere]

#1938 (comment)

The decoders are all in C, a fast but unsafe language. Python is significantly slower, but safe. This is a tradeoff that we should be able to make. (in either direction)

[ReedGraff]

Ok, well I'm honestly not sure how helpful I'm going to be here since I don't know C well enough to manipulate it into any specific format y'all might need, also given I'm not too familiar with how y'all's library is structured.

However, I went ahead and wrote the C-extension wrapper code for the library and got it compiling on my Windows & Linux machines, which is good enough for my use case, the README.md has an example of loading the bitmap from a jbg into PIL and then outputting to another format (would still be nice to have this natively tied into PIL, and not a separate library): https://github.com/ReedGraff/jbigkitpy

Additionally, I added some .jbg & .jbig files for reference in the assets/ folder, which you may distribute. Also attached here:
assets.zip

For anything beyond this I might need someone else to pick this up.

[stefan6419846]

I have stumbled upon this as well as part of reading PDF files with JBIG2 image streams in pypdf. When I looked into it back then, this mostly is a lack of available implementations which aren't under a viral license. In general, having Pillow support JBIG2 would be nice.

The current workaround/solution for pypdf is to use jbig2decode by Artifex, subject to AGPL-3.0 and thus very viral. Doing some testing has shown that pdfimages from poppler-utils would generate PNG files which are "somehow better" (I have not compared the output directly, but running Tesseract OCR on the pdfimages files proved to generate much better results than on the jbig2decode files.)

https://www.cl.cam.ac.uk/~mgk25/jbigkit/

This seems to be limited to JBIG1? Additionally, it is subject to GPL-2.0-or-later, thus imposing a viral effect and making Pillow unusable in commercial applications.

If you think that the patents are no longer a concern, please elaborate.

As far as I am aware, the patents primarily covered the encoder parts and never really were an issue with the decoder part. Additionally, the known ones (see https://www.hlevkin.com/hlevkin/Standards/fcd14492.pdf) might be expired (https://redirect.github.com/agl/jbig2enc/issues/58), although my knowledge regarding patents is too limited to do any final judgement on this.

[ReedGraff]

What are y'all thinking? Anyone open to working on this with more C experience? @stefan6419846 @radarhere

[stefan6419846]

I guess someone would already have indicated after starting to work on this and this is not trivial due to possibly requiring an implementation from scratch. Explicitly pinging users here most likely does not help with this. From my side, I neither have the necessary C experience nor the personal resources to do an actual implementation (otherwise I would already have looked into some alternative implementation for the libraries I maintain myself).