#wtfpdf — Public Fediverse posts

I’m adding a couple photos on file structure. #icabarcelona2025 #wtfpdf #digipres #odfa

Has anyone worked with ODF/A? Have it in your corpus? I found it interesting that one of the reasons for developing ODF/A was issues around Chinese characters in PDF (example: difficulties in copying from PDF). #digipres @wtfpdf #icabarcelona2025 #wtfpdf

#archivtagAT #archivtag2025 Andreas Rauber zeigt ein Beispiel von einem PDF, auch HTML hat oder als Virtual Machine gespeichert werden kann, die dann erweiterte Funktionen haben. Was passiert, wenn man so ein PDF normalisiert oder migriert wird? #wtfPDF

pdfalyze --help
(https://github.com/michelcrypt4d4mus/pdfalyzer)

outputs:

"Explore PDF's inner data structure with absurdly large and in depth visualizations. Track the control flow of her darker impulses, scan rivers of her binary data for signs of evil sorcery, and generally peer deep into the dark heart of the Portable Document Format. Just make sure you also forgive her - she knows not what she does."

#wtfpdf

On the effects of the useful

`mutool clean`

command to "repair" PDFs.

If you take this PDF https://openreview.net/pdf?id=CSJYz1Zovj and apply the command to it... the 27-page annex is cut off from the "cleaned" output (still in the PDF, but unreferenced, so not displayed).

So use it with care!

#wtfpdf

Well, I've finally made a blog post, but on the #OPF website!

https://openpreservation.org/blogs/validation-ok-they-said-fixing-the-rendering-of-a-so-called-valid-pdf

I'm walking you through the most complex (out of 2) PDF repair processes I've made. Any input is welcome!

#digipres #wtfpdf

Today's #wtfPDF moment: #PDFs with images that are encoded as #JPEG, where the JPEG data stream in turn is ascii85 encoded.

WHY?!? (The ascii85 encoding only inflates the JPEG data streams by 25% and doesn't offer any benefits).

https://github.com/KBNLresearch/pdfquad/issues/39

The smallest (valid) #PDF in the world is here:

https://pdfa.org/download-area/smallest-possible-pdf/smallest-possible-pdf-1.0.pdf

(source: https://pdfa.org/the-smallest-possible-valid-pdf/)

#digipres #wtfpdf

@edsu @quinnanya @bitarchivist @Literature_Geek This is a GREAT resource and I'd love to give this a boost, by WHY OH WHY is this published as a PDF where each page is a #!@@** JPEG image, which makes it 100% inaccessible (also, good luck copying and typing in all those hyperlinks) #wtfPDF

@mutanthumb @mickylindlar What? #wtfpdf @wtfpdf

https://phpc.social/@davidbisset/113799179388100004

#wtfpdf

ICYMI - are "octal escape sequences" in #PDF strings really a preservation risk, as claimed by the authors of the recent "The Phantom 👻 of a PDF File" blog post?

Some quick tests I did with eight different PDF processing tools suggest they're not, and #JHOVE's inability to handle them really seems to be the exception here #wtfPDF #fileformatfriday

https://www.bitsgalore.org/2024/11/14/escape-from-the-phantom-of-the-pdf

The authors of the recent "The Phantom of a PDF File" blog post argue that "octal escape sequences" in #PDF strings are a potential preservation risk.

But some quick tests with 8 different PDF tools suggest that #JHOVE is really the only tool that can't handle them!

Details in my new blog post "Escape from the phantom of the PDF" #wtfPDF 👻 :

https://www.bitsgalore.org/2024/11/14/escape-from-the-phantom-of-the-pdf

Update on the "Phantom of the #PDF" blog of a few weeks ago (link: https://digitalpreservation.fi/en/2024-phantom-pdf-file).

I did a little test of authors' claim that "#JHOVE probably is not the only software that will get confused" by octal escape sequences* in metadata strings

So I read the file with 8 different PDF tools/libraries:

https://github.com/openpreserve/jhove/issues/927#issuecomment-2465947326

Turns out JHOVE actually *is* the only software that gets confused by this #wtfPDF!

*) The authors describe this as "dual encodings", but see Peter Wyatt's comment!

Here's a sneak peek at a #PDF Quality Assessment tool I'm working on for digitisation batches , mostly based on #PyMuPDF, #pillow and #Schematron:

https://github.com/KBNLresearch/pdfquad

(Wouldn't recommend this for production yet, as it's not completely finished, and I'm still changing some things around.)

#wtfPDF

Here's a sneak peek at a #PDF Quality Assessment tool I'm working on for digitisation batches , mostly based on #PyMuPDF, #pillow and #Schematron:

https://github.com/KBNLresearch/pdfquad

(Wouldn't recommend this for production yet, as it's not completely finished, and I'm still changing some things around.)

#wtfPDF

Here's a sneak peek at a #PDF Quality Assessment tool I'm working on for digitisation batches , mostly based on #PyMuPDF, #pillow and #Schematron:

https://github.com/KBNLresearch/pdfquad

(Wouldn't recommend this for production yet, as it's not completely finished, and I'm still changing some things around.)

#wtfPDF

Here's a sneak peek at a #PDF Quality Assessment tool I'm working on for digitisation batches , mostly based on #PyMuPDF, #pillow and #Schematron:

https://github.com/KBNLresearch/pdfquad

(Wouldn't recommend this for production yet, as it's not completely finished, and I'm still changing some things around.)

#wtfPDF

Here's a sneak peek at a #PDF Quality Assessment tool I'm working on for digitisation batches , mostly based on #PyMuPDF, #pillow and #Schematron:

https://github.com/KBNLresearch/pdfquad

(Wouldn't recommend this for production yet, as it's not completely finished, and I'm still changing some things around.)

#wtfPDF

OMG, I played this game https://www.dpconline.org/blog/wdpd/blog-fff-game-wdpd2024 and my file format fling was PDF!?! #WTFPDF @wtfpdf #digipres #wdpd2024

Got my first PDF 2.0 file into my repository. Didn’t know Word was saving to the new format! #digipres #fileformats #wtfPDF

at the cost of giving away my anonymous response to this form ... here's a lesson on "read all options before answering" .... #wtfPDF

Next-level #wtfPDF shenanigans in this piece on exploiting #PDF browser rendering discrepancies:

"In this article, we will show you how to create a hybrid PDF that abuses widget annotations to create render discrepancies, and share the code so you can generate your own."

https://portswigger.net/research/fickle-pdfs-exploiting-browser-rendering-discrepancies

(via @decalage on the former birdsite)

Gave a lecture this morning about #PDF and #EPUB, as part of our "Summer School" program for young researchers.

Pleased to see that @sclaeyssens posted a photo of my peak-#wtfPDF slide on the birdsite, which compares extracting text from PDF to converting hamburgers into cows.

a recent veraPDF github issue discussion linked below got me thinking about file format identification and #wtfpdf
when a file is a PDF 1.7 and a PDF/A-1b, for example, we typically give preference to the stricter profile (PDF/A-1b). But what if a PDF is e.g. a PDF1.7, a PDF/A-2a and PDF/UA-1? While most identification tools return multiple fmt hits, most digipres systems -afaik- work on a "1 file format per file" basis. Curious to hear from anyone who assigns multiples.
https://github.com/veraPDF/veraPDF-library/issues/1456#issuecomment-2154981602

@mickylindlar @Thorsted for “Only errors in the files,” it’s gotta be #wtfpdf. This would actually be so fun for #WDPD (World Digital Preservation Day)

What's so hard about #PDF text extraction? ​

https://web.archive.org/web/20230107081641/https://filingdb.com/b/pdf-text-extraction

Good overview piece from 2020, sadly only available on @internetarchive because the original website is gone #wtfPDF #WheelOutTheDigitalDarkAgeKlaxon 📯

Getting closer to a #WTFPDF specification! @mickylindlar @wtfpdf #digipres https://pdfa.org/wp-content/uploads/2024/02/Well-Tagged-PDF-WTPDF-1.0.pdf

Somehow these days it's impossible for me to say anything about #PDF in a presentation without including a slide with the "old man yells at PDF" meme. I wonder how that happened #wtfPDF

#wtfPDF

"The 78,000 page PDF"

https://www.youtube.com/watch?v=ZvVNRRQjDh8

@bitsgalore Old man yells at PDF. 😅 Priceless! #WTFPDF

I've got some #wtfPDF questions. Can anyone recommend a tool for unlocking a password protected PDF if you don't have the password? Or how do people handle these other than not accepting them for transfer?

while PDF is something of a life partner for me, 3D data is something that always excites me .... sorry #wtfpdf ... still love ya.

#digitalpreservationlife #4CultureBarcamp

while PDF is something of a life partner for me, 3D data is something that always excites me .... sorry #wtfpdf ... still love ya.

#digitalpreservationlife #4CultureBarcamp

while PDF is something of a life partner for me, 3D data is something that always excites me .... sorry #wtfpdf ... still love ya.

#digitalpreservationlife #4CultureBarcamp

while PDF is something of a life partner for me, 3D data is something that always excites me .... sorry #wtfpdf ... still love ya.

#digitalpreservationlife #4CultureBarcamp

while PDF is something of a life partner for me, 3D data is something that always excites me .... sorry #wtfpdf ... still love ya.

#digitalpreservationlife #4CultureBarcamp

I explored to what extent #VeraPDF and #JHOVE can be used to identify #PDF features that are potential preservation risks. Check out this (massive!) blog post for the full lowdown #wtfPDF:

https://www.bitsgalore.org/2023/05/25/identification-of-pdf-preservation-risks-with-verapdf-and-jhove

A l'#OPFOAG hier, bribe de conversation volée : "si je n'ai plus de cheveux sur le crâne, c'est à cause de #PDF." #wtfpdf
Ça donne le ton. Sur le PDF, on a un énorme chantier à mener.

"PDF are in particular difficult .." says Carl Wilson at #OPFOAG

Truer words cannot be spoken.
#wtfpdf