Allow base64 encoding of CGM data when creating NITF files

[hikergreg]

When creating NITF files with CGM data, the user provides the binary CGM data in a char* with minimal escaping (see SEGMENT_0_DATA field at ​http://www.gdal.org/frmt_nitf_advanced.html).

This works fine with the C/C++ interface, but an issue arises with the Java bindings. In Java, the binary data is put in a String object, but the Java native level interprets Strings as being UTF-encoded by default. This borks up the data transfer.

My suggestion is to add a flag that would allow for the CGM data to be provided using base64 encoding instead of the default backslash-quotable. For example: SEGMENT_0_DATA_ENCODING=base64.

I've attached a patch with a proposed implementation for NITF/CGM creation. I can come up with some edits to the documentation as well.

[hikergreg]

Proposed patch

[Even Rouault]

Yes, an update of the doc would be appropriate

[Even Rouault]

Still waiting for an update of the doc

[Even Rouault]

This ticket has been automatically closed because Trac is no longer used for GDAL bug tracking, since the project has migrated to GitHub. If you believe this ticket is still valid, you may file it to ​https://github.com/OSGeo/gdal/issues if it is not already reported there.