[gdal-dev] HTJ2K decoding available in openjpeg master

Even Rouault even.rouault at spatialys.com
Sat Sep 25 04:52:41 PDT 2021


below is of potential interest for GDAL. We had related discussions when 
a Grok GDAL driver was proposed. HTJ2K (ITU-T.814 
https://www.itu.int/rec/T-REC-T.814-201906-I/en or JPEG2000 Part 15) is 
an extension of regular JPEG2000 were the code block encoding, which is 
the slowest part of JPEG2000, has been replaced by an alternative that 
has the potential for being 10 times or more faster (could apparently be 
30 times faster for lossless), with an increased file size of ~ 7%. 
Current implementation in OpenJPEG is "only" twice faster.

I've verified that the current JP2OpenJPEG driver, when linked to 
openjpeg master 2.5.0dev, can decode HTJ2K codestreams. This also works 
when they are embedded in JP2 boxes (files with .jph extensions that are 
similar to .jp2), which is in particular where georeferencing is encoded 
(GMLJP2 boxes or GeoJP2 boxes), so theoretically we should be ready for 
geospatial imagery using HTJ2K coding, if such a beast ever emerges...

This is a decode-only implementation. To play with the encoding side, 
you'll have to use https://github.com/aous72/OpenJPH, 
https://github.com/GrokImageCompression/grok or Kakadu


-------- Message transféré --------
Sujet : 	[OpenJPEG] HTJ2K decoding + github action workflows
Date : 	Sat, 25 Sep 2021 13:36:22 +0200
De : 	Even Rouault <even.rouault at spatialys.com>
Répondre à : 	openjpeg at googlegroups.com
Pour : 	OpenJPEG <openjpeg at googlegroups.com>


some good news to share about latest developments in OpenJPEG master branch:

- Aous Naman has made a great contribution by adding a HTJ2K (High 
Throughput / Part-15) decoder. See 
https://github.com/uclouvain/openjpeg/pull/1381 for details and 
limitations. My quick experiment (see 
shows a ~ x2 speed improvement in mono-threaded decompression compared 
to regular Part-1 code block style.

- I've migrated most of the continuous integration target to github 
action workflows. The driver for this is that Travis-CI is no longer 
friendly to open source projects due to a limited small quota that was 
exhausted for our project. github action workflows are naturally 
inherited in forks, so you can potentially work on a branch for some 
time, push in your clone, check CI results and just issue a pull request 
when you're done.


My software is free, but my time generally not.

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