Post without Account — your post will be reviewed, and if appropriate, posted under Anonymous. You can also use this link to report any problems registering.

CTS 2 - Heights and widths exceeding 200 inches

  • 0 Replies
  • 1094 Views
*

Offline Phil

  • Global Moderator
  • Sr. Member
  • *****
  • 359
    • View Profile
CTS 2 - Heights and widths exceeding 200 inches
« February 19, 2017, 05:14:00 PM »
Per article page width limit of 200 inches, PDFs have some constraints on their document sizes. While 200 inches on a side is plenty big for most applications (indeed, it could cover the Mt. Palomar Hale telescope's mirror), apparently some people have seriously tried to make larger documents.

Quote
In PDF Reference, Fifth Edition, version 1.6 one can read (paragraphe 171, page 1033) :

    In PDF versions earlier than PDF 1.6, the size of the default user space unit is fixed at 1⁄72 inch.
    In Acrobat viewers earlier than version 4.0, the minimum allowed page size is 72 by 72 units in default user space (1 by 1 inch); the maximum is 3240 by 3240 units (45 by 45 inches).
    In Acrobat versions 5.0 and later, the minimum allowed page size is 3 by 3 units (approximately 0.04 by 0.04 inch); the maximum is 14,400 by 14,400 units (200 by 200 inches).
    Beginning with PDF 1.6, the size of the default user space unit may be set with the UserUnit entry of the page dictionary.
    Acrobat 7.0 supports a maximum UserUnit value of 75,000, which gives a maximum page dimension of 15,000,000 inches (14,400 * 75,000 * 1⁄72). The minimum UserUnit value is 1.0 (the default).

So the size limitation turns out to be a matter of "UserUnit" value. The problem would be solved if this value was an option in [HTML to PDF converter wkHTMLtoPDF], something like : --user-unit (default : 1)

and

Quote
So it sounds like there are two different size limitations happening: by PDF version number and by Acrobat.

PDF < 1.6 -- User Space Unit fixed at 1/72"
>= 1.6 -- User Space Unit may be set (UserUnit)

Acrobat < 4.0 -- maximum 3240 units square (45")
< 7.0 -- maximum 14400 units square (200")
>= 7.0 -- maximum 14400 units square AND maximum UserUnit 75000 (15E6")

Given that Acrobat is probably by far the most used PDF reader* (or at least Adobe products are), what should our maximum page sizes be for a given PDF version? Can we count on just about everyone being at Acrobat 7.0 or equivalent? Remember that there are still some businesses and government agencies who mandate IE 6 (!) for browsers, so it may be safer to stick to older limits.

* How do Adobe Reader and PDF plug-ins for browsers map to Acrobat's versions?

Note that the referenced PDF document is not the latest version. I haven't dug through this part of the PDF 1.7 definition yet, but it sounds like the only change in PDF is (as of 1.6) that "UserUnit" may be set (default: 1 Pt, maximum 75000 Pt). Perhaps a warning should be issued if measurements exceed 14400 UserUnits (tough luck to pre-Acrobat 4 users with a 3240 limit, or perhaps we could add another warning for them).

Needless to say, such a change requires that we pay attention to the PDF version being output. That has to be implemented first.
« Last Edit: February 26, 2017, 10:56:30 PM by Phil »