[poppler] PDF with layers

[Albert Astals Cid]

El dijous, 6 d’abril de 2023, a les 14:24:58 (CEST), Valerio Messina va 
escriure:
> On 4/4/23 8:09 PM, Pablo Rodríguez wrote:
> > Your statement is extremely broad and it might be false, since OCGs are
> > supported in poppler.
> 
> OK, sorry, maybe it is related to poppler-utils only
> 
> > In the merge you provided at the GitLab report, OCGs aren‘t merged in a
> > single OCG.
> > 
> > What might be the case here is that OCGs from the second document are
> > simply being ignored.
> > 
> > Since you provided two documents with exactly the same OCG names, it is
> > impossible to see that OCGs from the second document are simply ignored
> > (not their content).
> > 
> > This explains the behavior you describe in your bug report.
> 
> no, the pdfunite output has no layers, see below
> 
> > If you allow me one more comment, please create two minimal files with
> > one OCG each and merge them and explains what happens in the issue at
> > GitLab.
> 
> OK, I admit that three test files from open bug date 5 years ago are
> confusing.
> 
> 
> Lets focus on PDFlayers_tst3* files only, the last posted i the report,
> that are minimal and simple:
> 
> File 1, 4 layers: Level 1, Background 1, Level 2, Background 2
> gray circle on Level 1
> black rectangle on Background 1
> Level 2 and Background 2 are empty
> https://gitlab.freedesktop.org/poppler/poppler/uploads/40f9db4e9a18bbade826f
> 99d3036019b/PDFlayers_tst3_pg1.pdf
> 
> 
> File 2, 4 layers: Level 1, Background 1, Level 2, Background 2
> black circle on Level 2
> gray rectangle on Background 2
> Level 1 and Background 1 are empty
> https://gitlab.freedesktop.org/poppler/poppler/uploads/b91f5ea252ed31b2eb6be
> 756f5789040/PDFlayers_tst3_pg2.pdf
> 
> 
> The merged, 2 pages file generated by 'pdfunite' is:
> File 3, NO layers: All contents merged to one layer in both pag.1 and 2
> https://gitlab.freedesktop.org/poppler/poppler/uploads/96c05c385c3ab7f2d1e7d
> b7520715ad4/PDFlayers_tst3_pdfunite22.03.0.pdf
> 
> 
> The reference (expected) output shuold be:
> File 4, 4 layers: Level 1, Background 1, Level 2, Background 2
> gray circle on Level 1 pag.1
> black rectangle on Background 1 pag.1
> black circle on Level 2 pag.2
> gray rectangle on Background 2 pag.2
> https://gitlab.freedesktop.org/poppler/poppler/uploads/c10e8f6a1064e27b323ec
> c1583dc28f2/PDFlayers_tst3_Scribus1.5.3.pdf

You're a human and that's what you would want to happen.

From a machine point of view that seems rather a weird thing to do, i would 
expect the output to have 8 layers one for each of the original layers.

Cheers,
  Albert

> 
> 
> All 4 files are already linked in gitlab, last my two posts from past year.
> 
> > But if part of the issue you mention is guessing what is misbehaving in
> > poppler, this won’t help to speed up the potential fix.
> 
> yes, my knowledge of english is poor, so I cannot explain as I want,
> again sorry.