[gdal-dev] LJPEG Support for GDAL

[Christoph Gohlke]

Lossless JPEG is defined in the Annex H of the JPEG specification. 
<https://www.w3.org/Graphics/JPEG/itu-t81.pdf>

See also 
<http://fileformats.archiveteam.org/wiki/Lossless_JPEG_(original)> and 
<https://www.loc.gov/preservation/digital/formats/fdd/fdd000334.shtml>.

LJPEG compressed images can be found in DICOM, DNG, and NITF.

Libjpeg(-turbo) can't decode it and errors with "Unsupported JPEG 
process: SOF type 0xc3"

Libjpeg <https://github.com/thorfdbg/libjpeg> can read (write?) the 
format but is GPL licensed.

Christoph


On 6/16/2021 10:19 AM, Even Rouault wrote:
> Hum, your answer confuses me. Do you have a pointer to where LJPEG is 
> specified, and how different it is from JPEGLS ?
> 
> Looking at MIL-STD-2500C 
> (https://nsgreg.nga.mil/doc/view?i=4724&month=3&day=22&year=2021), it 
> mentions
> 
> C5 - Lossless JPEG
> 
> C6 - reserved values that will represent a future correlated 
> multicomponent compression algorithm
> 
> What I can say is that the GDAL NITF driver currently doesn't handle 
> C5/C6 (no connection with the CharLS driver)
> 
> Even
> 
> Le 16/06/2021 à 18:56, GeodudeKid a écrit :
>> LJPEG is lossless JPEG. Trying to produce a NITF that is 
>> representative of
>> the Image Compression (IC) field being set to C5 or C6. C5 should be for
>> LJPEG, and C6 is for JPEGLS. I was wondering if there's a separate driver
>> for lossless JPEG, or if JPEGLS is a catch-all for both compression
>> algorithms.
>>
>>
>>
>> -- 
>> Sent from: http://osgeo-org.1560.x6.nabble.com/GDAL-Dev-f3742093.html
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