Re: Bloody PDF boxes and cr*p marks!

[Henning Hraban Ramm via ntg-context <ntg-context@ntg.nl>]

> Am 12.10.2021 um 13:15 schrieb Hans Hagen <j.hagen@xs4all.nl>:
> 
> On 10/12/2021 12:36 PM, Henning Hraban Ramm via ntg-context wrote:
>> 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.

>> * 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.).

>> * ArtBox is neglectable for whole layouts (same as TrimBox might make sense), just interesting in \externalfigure.
> 
> also worthless

I agree.

>> 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.

>> 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.

>> * 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.

>> % ... 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 ;))

>> 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 ;)

>> 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.

> (i'm pretty sure that changes will themselves introduce new issues)

Probable.

> 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

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