Making a PDF that’s larger than Germany

Submitted ⁨⁨9⁩ ⁨months⁩ ago⁩ by ⁨Ninjazzon@infosec.pub⁩ to ⁨technology@lemmy.world⁩

https://alexwlchan.net/2024/big-pdf/

Some version of this has been floating around the Internet since 2007, probably earlier. This tweet is pretty emblematic of posts about this claim: it’s stated as pure fact, with no supporting evidence or explanation. We’re meant to just accept that a single PDF can only cover about half the area of Germany, and we’re not given any reason why 381 kilometres is the magic limit.

I started wondering: has anybody made a PDF this big? How hard would it be? Can you make a PDF that’s even bigger?

A few years ago I did some silly noodling into PostScript, the precursor to PDF, and it was a lot of fun. I’ve never actually dived into the internals of PDF, and this seems like a good opportunity.

Let’s dig in.

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Comments

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aeronmelon@lemmy.world ⁨9⁩ ⁨months⁩ ago
How do we know we’re not living inside a PDF right now?

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- kurcatovium@lemm.ee ⁨9⁩ ⁨months⁩ ago
  How could we possibly live in PDF when we’re obviously living in Excel table?
  
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- agamemnonymous@sh.itjust.works ⁨9⁩ ⁨months⁩ ago
  It’s always been Wankershim
  
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General_Effort@lemmy.world ⁨9⁩ ⁨months⁩ ago
Arrows pointing out from Germany indicating a pointless quest for more space. Why do I feel like I have seen that before?

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- eggymachus@sh.itjust.works ⁨9⁩ ⁨months⁩ ago
  Arrows Pointless
  
  Pick one
  
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  - victorz@lemmy.world ⁨9⁩ ⁨months⁩ ago
    Bravo. 👏⛳
    
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- xavier666@lemm.ee ⁨9⁩ ⁨months⁩ ago
  It’s a rerun!
  
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  - assassinatedbyCIA@lemmy.world ⁨9⁩ ⁨months⁩ ago
    The writers are getting lazy
    
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- Buddahriffic@lemmy.world ⁨9⁩ ⁨months⁩ ago
  I’m not sure what you’re referring to. Augustus’ legion might have painted a map like that but they were trying to escape their quest for more space and didn’t really have the time to make any maps about it what with all of the arrow and axe dodging they needed to do.
  
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RememberTheApollo@lemmy.world ⁨9⁩ ⁨months⁩ ago

I could keep going. And I did. Eventually I ended up with a PDF that Preview claimed is larger than the entire universe – approximately 37 trillion light years square. Admittedly it’s mostly empty space, but so is the universe.

So yes. It can be done.

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NeatNit@discuss.tchncs.de ⁨9⁩ ⁨months⁩ ago
The takeaway is that the format doesn’t have any limit, but Adobe Acrobat in particular implements an arbitrary cutoff size. Other readers, such as Firefox’s built-in PDF reader or Mac’s Preview, can handle any arbitrary size. The article ends with a PDF the size of the universe, weighing an unimaginable 549 bytes!

But that limitlessness can come at a cost: according to the article, Preview doesn’t handle UserUnit which should affect page size, while Acrobat (and Firefox) do. I’m guessing (gut feeling) Acrobat probably supports the most features overall, Firefox probably supports the vast majority of those used in practice, and Preview only allows Apple Approved™ PDF features and extensions deemed worthy of Their Appleness’s consideration. Chrome’s PDF reader is probably on the same level as Firefox, I guess.

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- abhibeckert@lemmy.world ⁨9⁩ ⁨months⁩ ago
  I’m guessing (gut feeling) Acrobat probably supports the most features overall, Firefox probably supports the vast majority of those used in practice, and Preview only allows Apple Approved™ PDF features and extensions deemed worthy of Their Appleness’s consideration.
  
  OK… stepping out of gut feelings into reality:
  
  Adobe originally had a maximum page size of 45 inches square.
  
  In 2001 they increased that to 200 inches
  
  And in 2004 they Adobe increased it to 15,000,000 inches (a bit larger than Germany)
  
  As for “Their Appleness’s consideration” they generally use 8 bit floating point numbers for this stuff. Which would make the maxium size 179769313486231570814527423731704356798070567525844996598917476803157260780028538760589558632766878171540458953514382464234321326889464182768467546703537516986049910576551282076245490090389328944075868508455133942304583236903222948165808559332123348274797826204144723168738177180919299881250404026184124858368 points.
  
  Which I’m pretty sure is bigger than the universe.
  
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  - NeatNit@discuss.tchncs.de ⁨9⁩ ⁨months⁩ ago
    
    Adobe originally had a maximum page size of 45 inches square.
    
    In 2001 they increased that to 200 inches
    
    And in 2004 Adobe increased it to 15,000,000 inches (a bit larger than Germany) which is still kinda sucky if you want to show a map on a PDF
    
    It’s unclear why Acrobat has to have a limitation at all, since other PDF programs have no such limitation. More importantly, Acrobat only supports up to 200.00 x 200.00 in (5.08 x 5.08 m) using the standard MediaBox setting - any higher than that and you get a warning. The only way to push past that is to also set a UserUnit value, which essentially acts as a multiplier. This is all detailed in the article.
    
    But Apple’s Preview doesn’t support UserUnit, meaning a PDF larger than 200 x 200 in can’t be displayed correctly in both Acrobat and Preview. If you set it higher using just MediaBox, then Preview will show it fine but Acrobat will truncate it. If you set MediaBox to the highest values Acrobat accepts and use UserUnit as a multiplier, then Acrobat will show it fine but Preview would not (I don’t know if it would truncate it or show it scaled down). So when it comes to PDFs larger than 200 x 200 in, you can choose either up to 15,000,000.00 x 15,000,000.00 in in Acrobat or as large as you like in Preview - you can’t have both.
    
    As for “Their Appleness’s consideration” they generally use floating point numbers for coordinates and sizes. Which is how, as it says in the OP’s article, it’s able to handle a PDF trillions of light years in size. A double precision floating point number can be really big.
    
    More important though, it means you can process it with hardware accelerated floating point operations which are incredibly fast. And Apple’s PDF renderer needed to be fast because for years PDF was the data format used by the window manager for pretty much all screen drawing operations. They weren’t doing that on modern fast hardware either, they were doing it decades ago on slow hardware. With decent performance.
    
    If there are features missing it’s probably because they would slow things down too much.
    
    All interesting and things I didn’t know, but this is completely irrelevant. A PDF-reading app (i.e. Preview) does not have to use, and almost certainly does not use the same PDF rendering engine as the desktop rendering one you described. An obvious relevant example is pages - the desktop renderer doesn’t need to know about or render pages at any point. It doesn’t deal with the size of a page, the existence of multiple pages, or pages of different sizes. It has only one canvas to draw in. A PDF viewer app OTOH obviously has to be able to handle all of these things, and render them into a format that can be pushed to the system’s graphics API.
    
    See this StackExchange answer, which quotes this paragraph from Ars Technica (emphasis mine):
    
    it is important to understand that Core Graphics Services deals with more or less “ready-to-display” data sent to it from higher layers in the graphics system. It is a pixel pusher, not a graphics creator
    
    It doesn’t deal with any features, whereas a reader app must deal with many features. So discussing it is irrelevant for the Preview app.
    
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Gork@lemm.ee ⁨9⁩ ⁨months⁩ ago
Clearly PDF is an outdated standard if it cannot handle files greater than 381 km x 381 km in size.

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- NeatNit@discuss.tchncs.de ⁨9⁩ ⁨months⁩ ago
  For real! How am I going to make a 1:1 map of Europe like this?!
  
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  - SirQuackTheDuck@lemmy.world ⁨9⁩ ⁨months⁩ ago
    There’s probably an emacs plugin for that.
    
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Diplomjodler@feddit.de ⁨9⁩ ⁨months⁩ ago

Eventually I ended up with a PDF that Preview claimed is larger than the entire universe

Printer’s out of toner. Can you fax it to me?

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- xavier666@lemm.ee ⁨9⁩ ⁨months⁩ ago
  Printer out of cyan ink
  
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visnae@lemmy.world ⁨9⁩ ⁨months⁩ ago
Fun fact, LaTeX is actually NP-complete so you can program whatever in it AND make it beautiful

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- user134450@feddit.de ⁨9⁩ ⁨months⁩ ago
  you mean turing complete?
  
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  - visnae@lemmy.world ⁨9⁩ ⁨months⁩ ago
    Yes sorry ofc
    
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far_university1990@feddit.de ⁨9⁩ ⁨months⁩ ago
𝕯𝖎𝖊𝖘𝖊 𝕶𝖔𝖒𝖒𝖊𝖓𝖙𝖆𝖗𝖘𝖊𝖐𝖙𝖎𝖔𝖓 𝖎𝖘𝖙 𝖓𝖚𝖓 𝕰𝖎𝖌𝖊𝖓𝖙𝖚𝖒 𝖉𝖊𝖗 𝕭𝖚𝖓𝖉𝖊𝖘𝖗𝖊𝖕𝖚𝖇𝖑𝖎𝖐 𝕯𝖊𝖚𝖙𝖘𝖈𝖍𝖑𝖆𝖓𝖉

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DirigibleProtein@aussie.zone ⁨9⁩ ⁨months⁩ ago
How can my manager print seven copies?

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- SoylentBlake@lemm.ee ⁨9⁩ ⁨months⁩ ago
  Fax it to him 😉
  
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uriel238@lemmy.blahaj.zone ⁨9⁩ ⁨months⁩ ago
Isn’t PDF vector (with pixel drop-in elements)? Those should be scaleable to the word size (e.g. 128 bit) But the problem with these like some open world games is a lot of empty space with few exciting features.

1200DPI the size of Germany, or even enough text to fill Germany with 12 point fot would be impressive.

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- NeatNit@discuss.tchncs.de ⁨9⁩ ⁨months⁩ ago
  Your aspirations are too tame.
  
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  - trolololol@lemmy.world ⁨9⁩ ⁨months⁩ ago
    It’s a niche hobby now, but next year we’ll be a dozen of us! Wait and see! Buahaha
    
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HootinNHollerin@lemmy.world ⁨9⁩ ⁨months⁩ ago
Stop! You’re making HP’s ink boner larger than Silicon Valley!

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TheRealKuni@lemmy.world ⁨9⁩ ⁨months⁩ ago
This is delightful.

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