[Gdal-dev] JP2KAK

[Mark Overmeer]

* Frank Warmerdam (warmerdam at pobox.com) [060628 16:16]:
> >It helped.  Everywhere I see references to read the ECW SDK... but the docs
> >of the SDK do not explain the options (at least: I cannot find it)
> 
> My copy of the ECW SDK source code includes an SDK.pdf file.  Circa page
> 113 is a section on the CNCSFile::SetParameter() call defining the meaning
> of various parameters affecting JPEG2000 creation.

Ok.  Problem solved: the compiled distribution contains a file
ER_Mapper_SDK.pdf which does contain some technical information about
the library, but the source distribution contains a file SDK.pdf which
contains real internals.

The reference to the parameters is there, but on the same level of
detail as on gdal's webpage: just listed.  This is typical for technical
documentation: describing the options without explaining the use. F.i:

 JP2_COMPRESS_BASELINE_0   Compress for Class 0 compliant Coders
 JP2_COMPRESS_BASELINE_1   Compress for Class 1 compliant Coders
 JP2_COMPRESS_BASELINE_2   Compress for Class 2 compliant Coders

could do with some words like:
 The higher the BASELINE, the better the compression, but the higher
 level is not always implemented and sometimes slower.

Above lines are certainly untrue, but what is the real meaning of the
options in user terms?  What is the effect on the output in size, quality,
portability.  That are questions the library user likes to have answered.
Of course, you get into polically difficult and subjective areas.

Anyway, I am very glad that I can convert anything to anything using GDAL,
although still uncertain whether I use the optimal settings.  Translating
20k satellite scenes, which takes me many weeks of computational
power, a little more assurance that this gives me the optimal results
(without the need to interpret the JPEG2000 specification in full detail
myself) was welcome.  Extend the wikipedia pages?

Thanks for your (as ever) fast, very clear, and to the point response.
-- 
Regards,
               MarkOv

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       Mark Overmeer MSc                                MARKOV Solutions
       Mark at Overmeer.net                          solutions at overmeer.net
http://Mark.Overmeer.net                   http://solutions.overmeer.net