Basic support for PDF/A-2 and PDF/A-3

[hvbargen]

Is your feature request related to a problem? Please describe.
PDF/A-3 is needed for ZUGFeRD (Factur-X) electronic invoices.
Besides, VeraPDF complains about PDF files generated with OpenPDF about CIDSet when I try to generate PDF/UA-1 (tagging works BTW).

Describe the solution you'd like
Constants in PDFWriter.java for PDF/A-2a, -2b, -2u and PDF/A-3a, -3b, 3u.
Similar to the existing constants for PDF/A-1 and with corresponding code adaptions where the existing PDF/A-1 constants are used
(PdfXConformance.java, XmpWriter.java, PdfXConformanceImp, TrueTypeFontUnicode.java).

Describe alternatives you've considered
I don't think there any alternative solutions, except maybe post-processing the PDF with Apache PDFBox ;-).

Your real name
Henning von Bargen

Additional context
I'm working on adding PDF/UA support to Eclipse BIRT.

[andreasrosdal]

Pull requests welcome. Thank you for reporting.

[hvbargen]

Hmm, I don't know what exactly is needed.

But let me share the issues I found when I was trying to create documents which conform to PDF/UA-1 and PDF/A-3a at the same time - finally, with success, see my work on PDF/UA support for Eclipse BIRT.

First of all, there are now constant or whatever to declare conformance with newer PDF/A versions.
There are int constants for PDF/A-1a and PDF/A-2b, but not for the newer versions.

For my own work, I just added additional constants in one of my files, see file PDFPageDevice.java and look for the comment
// FIXME THis is a workaround for the fact that OpenPDF does not support PDF/A-2.

Note: I did not a add a constant for PDF/A-4e, because I think I'm not going to support creating this with BIRT.

Next, it was surprisingly difficult to create a PDF file which conforms to PDF/A and PDF/UA at the same time.
That's not OpenPDF's fault, of course - it's the PDF/A specification which makes this so difficult My solution was to create suche a PDF with LibreOffice Writer and look at the XMP metadata. In my code I added a private class PDFAExtensionSchema which generates the XML directly in its toString() method, suitable for being called with addRdfDescription if the document shall be PDF/A and PDF/UA at the same time.

I think a similar utility method would be a good addition for OpenPDF.

The XmpWriter is not directly usable for my use case, because it will only write the PDFA1Schema (well, of course) if PDF/A-1 is specified. However, the schema can be used (despite its name) also for PDF/A-2, 3, or 4, if one calls addPart("2") and addConformance("A") or whatever after the construction.

[speckyspooky]

+1 to add additional support of PDF/A-version through OpenPDF.
This would increase the common usability of OpenPDF for PDF/A
and reduce the implementation efforts to realize the generation of different PDF/A-versions.

[p3rh2n]

+1 to add additional support of PDF/A-version through OpenPDF.

PDF/A-n-compliant documents are increasingly required in the specifications of the public digital infrastructure, see ZUGFeRD, ePA4ALL,... for Germany.