Add experimental PDF/A compliance mode

[Starfox64]

This PR adds experimental PDF/A compliance mode and closes #1106

I'm calling this experimental for multiple reasons:

• Currently only supports the CPDF backend
• Only takes care of adding the required metadata
• Doesn't force font embedding, it's on the user to embed their fonts
• I can only test so many documents, the user should generally verify actual compliance with a tool like veraPDF (profile PDF/A-3b) and report issues
• Isn't as robust GhostScript

This still should work for most people on non esoteric documents.

Addendum

Fixes #3442

[williamdes]

Can you say where you got this file?
What licence it is?
Is this the same file as https://sources.debian.org/src/tcpdf/6.7.4%2Bdfsg-1/include/sRGB.icc/?

[Starfox64]

Source: https://www.color.org/srgbprofiles.xalter
License: https://www.color.org/profiles2.xalter#license

[williamdes]

Thank you!
Let's let @bsweeney let us know if adding a licence file should be done like in https://github.com/dompdf/php-font-lib/tree/master/tests/resources/fonts/ahem

[williamdes]

The diff looks good, maybe some concerns about the licencing of the binary file

[williamdes]

@Starfox64 do you think it would solve #3269 ?

[Starfox64]

That's the wrong Issue ID I think.

[williamdes]

Indeed, this one: #3442

Could you rebase your work ?
I was about to try it but composer wants 2.1+

🇫🇷 👋🏻

[Starfox64]

I've done a merge recently and it looks like I'm ahead of master.

With regards to #3442 I think this might be fixed by this line https://github.com/dompdf/dompdf/pull/3269/files#diff-f365bcb24d5c081b6bfde4aa59a8eda68824ea9658c362098554fc659dcec1d0R3426

It's funny to see that we are literally trying to do the same thing btw, nothing spells out fun more than trying to embed XML in PDF metadata.

[williamdes]

I've done a merge recently and it looks like I'm ahead of master.

With regards to #3442 I think this might be fixed by this line https://github.com/dompdf/dompdf/pull/3269/files#diff-f365bcb24d5c081b6bfde4aa59a8eda68824ea9658c362098554fc659dcec1d0R3426

It's funny to see that we are literally trying to do the same thing btw, nothing spells out fun more than trying to embed XML in PDF metadata.

Okayy, I got it wrong: barryvdh/laravel-dompdf[v2.1.0, ..., v2.1.1] require dompdf/dompdf ^2.0.3
So I will "downbase" your work and test it for 2.0

[williamdes]

https://github.com/williamdes/dompdf/tree/pdfa-2.0

and https://github.com/williamdes/dompdf/tree/feat/pdfa is a rebased version without merges

[bsweeney]

FYI I'm re-targeting this to 3.1 (from 3.0.1) since it's a new feature not a patch. I know there are a lot of issues slate for 3.0.x releases but I suspect most of those will be pushed out once I have a chance to review them.

[williamdes]

Can you add Fixes: #3442 to this PR ?
It passes nearly all compliance tests except

[Specification: ISO 19005-3:2012, Clause: 6.2.11.4.1, Test number: 1](https://github.com/veraPDF/veraPDF-validation-profiles/wiki/PDFA-Parts-2-and-3-rules#rule-621141-1)	
The font programs for all fonts used for rendering within a conforming file shall be embedded within that file, as defined in ISO 32000-1:2008, 9.9.	Failed

Let's follow up on #3443