[Openicc] Print and monitor Color Pipeline

[Jan-Peter Homann]

Hello Leonard and all,
Some comments in the text:

Am 26.01.11 23:16, schrieb Leonard Rosenthol:
> Flat color documents:
>
>     2b) new school is directly to create PDF for the printout. All PDF
>     content would be either DeviceRGB or DeviceCMYK with an Output
>     Intent describing the document colorspace. Colormanagement will be
>     applied after rasterization.
>
>
> ASSUMING that there was no transparency in the content, then you could 
> do it this way - otherwise, you need to color manage as part of the 
> rasterization.   Also, if the OutputIntent doesn't match the printer 
> and the document is CMYK, you could get a 4-3-4 conversion (whihc no 
> one wants).
Jan-Peter:
I´m talking here about "flat color documents, where all parts of the 
documents have the same colorspace which is decribed by the output 
intent. So flattening transparencies will hve no impact on color.

The Case of 4-3-4 (CMYK-Lab-CMYK) conversion is only critical for 
PDF-2-PDF conversions / optimization. For printing CMYK-PDF files, such 
conversion are daily business.

>     3) Complex Mixed color document
>     ************************************
>     This are RGB or CMYK documents with text, images and
>     vectorgraphics can have individually embedded ICC profiles.
>     3a) PostScript must be avoided for the printdata of such
>     documents, because handling of ICC-profiles in individual elements
>     is a nightmare in PostScript.
>
>
> Yup!
>
>     3b) Direct creation of PDF for the printstream is a MUST. As a
>      user also expects a correct match to the monitor, the graphics
>     libray in use should have the option to rasterize for print out on
>     non PDF/PostScript print-worklflows.
>     If the printdata is not colormanaged direct by the graphics
>     library, the created PDF for the print stream should contain both
>     profiles for individual objects and also one profile describing
>     the colorspace of the complete document (PDF output intent)
>
>
> You need to watch this, since this is what Quartz does.  And while 
> perfectly valid, many professional printers will go nuts about having 
> text and vectors with ICC profiles assigned.  (just sat through 
> ANOTHER presentation, just this morning, at the Ghent Workgroup where 
> they ranted about this particular issue).

The problem of Quartz is changing every DeviceRGB or DeviceCMYK object 
to ICCbasedRGB or ICCbasedCMYK. This is especially problematic for 
DeviceCMYK objcets in the graphic arts.

In never understood, why Quartz is doing that. They could leave 
DeviceCMYK objects as they are and add only an output intent.
>
>     If the OutputIntent of the print stream PDF is not identical with
>     the ICC-profile of the current printer setting. The PDF-rendering
>     and rasterizing should be done firstly to the document colorspace
>     and than to ICC of the printer driver setting.
>
>
> Nope!   You should follow the rules for PDF rasterization and color 
> management as defined in ISO 32000.
>
If PDF/X files are proofed, all ICCbased PDF objects are converted 
through the embbeded profiles and rendering intents to the Output Intent 
and than the file is converted to the printer colorspace. That how all 
professional proofing systems are working...

Best regards
Jan-Peter

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