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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