Re: [NTG-context] Bloody PDF boxes and cr*p marks!

12 Oct 2021

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Am 12.10.2021 um 13:15 schrieb Hans Hagen :
On 10/12/2021 12:36 PM, Henning Hraban Ramm via ntg-context wrote:
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Comrades!
There must have been a time when PDF boxes (i.e. CropBox, TrimBox, BleedBox) worked as they should, but it must have been a short time.
I long ago lost track of what all that means ... decades of pdf ... different viewers, different interpretations ... validators complaining about things missing ... i guess that bit (like annotations) will always be in flux (also because specs came before implementations i guess).
Hm, you implemented these boxes only in 2015, there was not much change in that regard since then.
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* BleedBox must be TrimBox plus bleed.
a relative new one, probably also sensitive for interpretation by renderer, imo worthless
Not worthless; workflow systems in printshops rely on BleedBox and TrimBox. It’s not about rendering, but imposition and even postprocessing (cutting etc.).
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* ArtBox is neglectable for whole layouts (same as TrimBox might make sense), just interesting in \externalfigure.
also worthless
I agree.
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With
\setuppaper[A4][A4,oversized]
I’d expect ConTeXt to set...
* MediaBox and CropBox to the bigger format
* TrimBox to the page format (A4)
* BleedBox also to the page format, while no bleed is defined
well, that's an assumption ... who knows what a printer (driver) does ...
Who sends PDF files directly to a printer (driver)? I know it only from automated, professional workflows.
Usually printer drivers gets fed by PDF viewers, and I know none that even *can* print something different than CropBox.
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Beware, \setupbleeding refers only to stretching of images (\externalfigure)!
fwiw, that bleeding options is mostly there to communicate with mp
Good to know. I just browsed the Details manual, didn’t try it yet, since I scale and move my “bleeding” images differently.
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* to define trimoffset, I must know the difference between paper size and sheet size ("oversized" adds 15 mm).
oversized is a convenience feature, in prepress one would define a real, target size, not rely on a convenience value
But it’s convenient ;) I usually just need a format that is big enough for the crop marks, and “oversized” does that.
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% ... and no dependency on interactionscreen!
that's a historic fact ... special pdf features triggered by that command .. basically tex only has a page size
Of course, but it doesn’t make sense any more, and defining the boxes wouldn’t hurt anyone. (I’m quite sure, but let them beat me ;))
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Yes, that would mean a backward incompatible change. But how many of us rely on the strange current behavior?
Please let us fix this!
the problem is as usual documentation and indeed we can have some backward compatibility issue here ... i honestly have no clue how viewers and printers react (so if something would be added/changed it would be option driven)
I wouldn’t expect printers (office printing devices) to react at all; I hope that printers (printshop workers) will react positively to correct boxes in our PDFs ;)
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In some cases it makes sense to have different values on e.g. inner and outer edges; I feat that would add a plethora of additional parameters (leftbleedoffset, innerbleedoffset...).
Maybe give a list like in CSS? bleedoffset={3mm,3mm,3mm,0mm} – top, right, bottom, left order implied; not very “ConTeXt style”.
probably spreads need some treatment (imposition)
Multiple pages on a sheet are not considered by the PDF specs.
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(i'm pretty sure that changes will themselves introduce new issues)
Probable.
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anyway, we can look at it once we're all on lmtx because i'm not going to change mkiv in that aspect
Ok

Hraban