[Printing-architecture] Make use of extended color spaces on IPP printers

Solomon Peachy pizza at shaftnet.org
Sun May 9 02:24:42 UTC 2021


On Sat, May 08, 2021 at 09:24:27PM -0400, Michael Sweet wrote:
> >    its native/preferred colorspace.  (It's called various things in 
> >    UIs, such as "disable color correction" or "host-managed color")
> > 2) The job *must* support embedding an arbitrary ICC profile
> 
> Not the Job.  The *Document*.

Thanks for the correction -- I'm not as familiar with the IPP 
terminology as I should be.

> > handful of colorspaces via ColorSpaceEnum; eg DeviceRGB, sRGB, and 
> > AdobeRGB.  This is a weakness vs JPEG or PDF (which allows arbitrary 
> > profiles.  Can we rely on that ColorSpace field being set correctly?
> 
> First, yes.  We've been doing so for years, even with Ghostscript 
> (which typically converts everything to sRGB).

Excellent.  But I'm thinking more of folks trying to print something 
from a random app on their their iOS or Android devices.  Having a rich 
standard doesn't help when the client implementations are all 
differently brain-dead. :)

> Second, it isn't a weakness to support well-known RGB color spaces 
> along with a device RGB color space. 

I'm sorry, that's not what I was trying to say.

The "weakness" is that the PWG raster format doesn't have a way to 
self-describe what "Device RGB" means, unlike more standalone image 
formats (eg jpeg, png, tiff) that have a standard method to embed ICC 
profiles.

Now if PWG raster data can only exist (or be submitted) within a 
"Document" that explicitly supports embedding an ICC profile, that's 
another matter, but that goes back to my worry about brain-damaged 
clients that don't do the right thing.

(And trying to accomodate those brainead clients possibly breaking stuff 
 that does properly adhere to the spec..)

> Printers that only support PWG/Apple raster really don't offer much in 
> the way of color management. 

True.

(But PWG raster is mandatory, lossless, and a lot less complicated to 
 implment than PDF or the TIFF abombination..)

 - Solomon
-- 
Solomon Peachy			      pizza at shaftnet dot org (email&xmpp)
                                      @pizza:shaftnet dot org   (matrix)
High Springs, FL                      speachy (freenode)
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