Reputation: 9140
From what I have understood, at least PDF, especially its PDF/X standard, allow one to embed information on page bleed and such, with BleedBox
command.
I wonder, would Postscript also allow such things, and is PostScript a good "place" to specify them, or have I misunderstood its purpose? Since PostScript data is designed to be sent to the printer, wouldn't it be natural to be able to specify bleed?
I cannot find any reference to this in PostScript documentation:
http://www.adobe.com/products/postscript/pdfs/PLRM.pdf
Upvotes: 0
Views: 189
Reputation: 2205
See Adobe TN 5644 (PDF), and page 6 illustration in particular. Then make sure that your print provider's postscript consumer application (workflow) understands the %%CropBox
comment for trim ...
Upvotes: 0
Reputation: 11405
Yes, the PostScript language allows you to specify "page bleed and such". And if set your frame of reference to be modern print publishing overall, then No, a PostScript language page description is not a good place to put the high-level requests, but Yes, it's the best possible place for some of the low-level results of such requests. At lot hangs, of course, from what exactly you mean by "page bleed and such", and by how you frame the system you are looking at.
By "page bleed", I understand you to mean drawing colours up to and beyond the limits of the desired page, especially when the physical medium is larger than the intended page and will be cut to size. That allows the colour to come right to the edge of the finished page. This is part of a print publishing process, which prepares a document for the physical realities of a printing process like offset printing. Other tasks might be trapping, adjusting the shapes on the page to allow for poorly registered colourants; imposition, laying out multiple document pages on a large physical sheet that is later folded or cut; spot colour invocation, using an ink premixed to a specific desired colour rather than the CMYK process colours; and many more.
Modern prepress workflows involve moving content between systems and between organisations. Systems might include layout software where the document is designed and created, preflight software that ensures that the document contains all the fonts and images and other parts it needs, imposition and trapping systems that prepare it for a specific printing press, platemakers that turn the document into metal plates for the press, and perhaps a workflow system to keep track of the job all through this process. The people might include a document author, a designer who does the layout and font selection, a prepress technician who prepares the document for the prepress workflow, operators for the various systems, and so on.
With that context set, what role does a PostScript language page description play? A good place to start is in the PostScript Language Reference Manual (PLRM), section 6.1 Using Page Devices. A crucial concept there:
It is useful, at least in concept, to envision two separate tasks when printing from an application:
- Generate a device-independent page description.
- Request that the page description be rendered on a particular device. At this point, the user should have an opportunity to add processing options, including device-dependent ones, to the page description.
Bleeds, trapping, imposition, and so on are device-dependent. They aren't helpful in a device-independent page description. It is possible to author PostScript language page descriptions so that they are quite device-independent. But other formats, notably the PDF/X profile of the Portable Document Format, are even better device-independent containers for the early part of a prepress workflow. Adobe created PDF in part from its experience of the strengths and weaknesses of expressing device independent page descriptions in the PostScript language.
It's necessary to have a way to communicate requirements and print options throughout. Formats like Job Definition Format (JDF) are even better for this communication than PDF/X or PostScript language page descriptions. As a general rule, a format like JDF is a better place to express requests for "page bleeds and such" than a page description.
But at some point in the process, the device-independent page description gets targeted to a specific device. It's at this stage that the page description might get transformed into a device-specific PostScript language page description. The PostScript language has several features to support prepress features with some, but not too much, device-specific knowledge.
setpagedevice
operator provides a way to request device-specific features in a consistent way, with a provision for the job to continue even if the device can't fulfill all the requests. See PLRM, 6 Device Control.So in summary, I'd say that your question implies a frame of reference — just the PostScript language, and just a part of the print workflow — which is not the best for understanding how print publishing actually gets done. Setting a more general frame of reference, we see that the PostScript language has great features to accomplish its job in the workflow, but other formats like PDF/X and JDF also accomplish part of what you are asking about.
Upvotes: 1
Reputation: 31199
PostScript is, fundamentally, a programming language designed for 2D graphical applications. In general it is used to print but it has been used as a Windowing system on Unix workstations. Although primarily used for printing this is not its sole purpose.
Things like 'Bleed' are essentially metadata, they refer to aspects of the job other than actually marking the media. PDF carries considerable quantities of metadata, PostScript does not. So in general, the answer to your question is 'no'.
That said, there is a specification for adding metadata of various kinds to PostScript files, the Document Structuring Convention. This uses PostScript comments, written in a particular fashion, to carry metadata. You can find the DSC spec on the Adobe site somewhere.
As for specifying bleed, the PostScript program doesn't care, it just marks the media where you tell it to, so specifying bleed doesn't make sense to it.
Upvotes: 2