[Openicc] GoSoC 2011: CPD and target printing

Michael Sweet msweet at apple.com
Fri May 13 15:41:57 PDT 2011

On May 13, 2011, at 3:26 PM, Chris Murphy wrote:
>> ...
>> None of these things requires a dedicated app - RIPs already provide them on Mac OS X.
> A RIP is a dedicated app.

Not always. RIPs can be general purpose programs in the CUPS filter chain, replacing the default one in Mac OS X (cgpdftoraster) or embedded in a larger printer-specific solution (which is how a lot of them are packaged for the Mac...)

> Are you seriously suggesting that rendering intent control and black point compensation belong on a RIP, and not in the print driver and not in Photoshop? That's a total non-starter for a meaningful conversation about sticking to Mac OS as a platform.

I am saying that if you want a custom CMM for all printing, the place to put it is in a RIP if you want it to apply to all applications.  Standalone "drag a file onto the RIP application icon" RIPs are a non-starter IMHO since they make it too hard for a user to print using the RIP.  Application color management has similar issues since you only get the special CMM for content from that app.

> ...
> a.) Most applications do not use kPMApplicationColorMatching. Only two use it right now as far as I know. I'm not suggesting all applications be capable of producing /DeviceRGB in PDF print spools, just those applications that call kPMApplicationColorMatching for the express purpose of disabling ColorSync for printing profile targets and prematched image data.

That is, in fact, one of my "pitches" for the simple API.

> b.) There is no user or application access to the pdf print spool file.

PDF workflows (which were added in 10.4 I think) give you access, and CUPS allows the owner of a job to access the spooled jobs since 10.6.

> ...
> c.) If an application tags data Generic RGB and submits it to the OS, it's changed by the Quartz PDF Context into sRGB.

Actually, it is technically Generic RGB Gamma 2.2, which looks a lot like sRGB. And that is only for the convenience functions in CG, not for image content.

Michael Sweet, Senior Printing System Engineer, PWG Chair

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