> So you would have a XML file that would point > to the beginning of the .jp2 file, then an auxiliary file with the TLM > marker, and then the rest of the .jp2 file, and then you open > /vsisparse/my_patched_jp2.xml . I believe that should work because there > are no absolute offsets in JP2 files.
Thank you for the idea, indeed this works great, the implementation is straightforward, and it doesn't require any change on GDAL/OpenJPEG! So let's discard the tlm sidecar idea. Le ven. 13 déc. 2024 à 17:47, Even Rouault <even.roua...@spatialys.com> a écrit : > > > > > If you are not against the .tlm sidecar idea in GDAL/OpenJPEG, that's > > good enough for me for now, and it might allow further discussions > > with ESA. > > Well, you should tell them I'm actively *against* the sidecar idea to > motivate them doing the proper thing, otherwise they'll have little > incentive to move :-) > > I just said it can be technically done (what can't ?), not that I'm a > big fan of it. That would be purely a openjpeg change. > > Actually, if you only target GDAL, you could do something that requires > no change neither in GDAL or openjpeg, which would be a variation of > rewriting a new .jp2 file with the TLM marker without actually rewriting > them. GDAL has a rather little-known /vsisparse/ virtual file system (Cf > > https://gdal.org/en/stable/user/virtual_file_systems.html#vsisparse-sparse-files) > > where you can point at a XML file that concatenates portions of various > files into a virtual file. So you would have a XML file that would point > to the beginning of the .jp2 file, then an auxiliary file with the TLM > marker, and then the rest of the .jp2 file, and then you open > /vsisparse/my_patched_jp2.xml . I believe that should work because there > are no absolute offsets in JP2 files. > > -- > http://www.spatialys.com > My software is free, but my time generally not. > Butcher of all kinds of standards, open or closed formats. At the end, > this is just about bytes. > >
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