[Openicc] Printing targets: App or driver ? Profiling RGB or CMYK

edmund ronald edmundronald at gmail.com
Tue May 17 16:13:25 PDT 2011

On Wed, May 18, 2011 at 12:41 AM, Chris Murphy <lists at colorremedies.com>wrote:

> We are talking primarily about Gutenprint inkjet printer drivers, correct?
> If so, I could better understand how the driver presently functions with
> respect to internal transforms.
> Some inkjet printers are CMYK, most have more than four colorants. But most
> of those consumer printers with more than four colorants don't provide
> access to individual channels, i.e. DeviceN not possible. Michael Sweet has
> pointed out a while ago that this is trending all the more toward sRGB only
> input. So we have variable input color modes and spaces for inkjet printers.
> 1. If a printer has an sRGB path, I think that needs to be made directly
> available to the user, unmodified, so they can have platform parity.
> 2. Not clear to me is the exact nature of alternative paths to these
> printers, when available. Are they unspecified RGB? CMYK? Or DeviceN? I know
> on the Pro Epson printers there is DeviceN.
> 3. If DeviceN is available, how is this utilized by Gutenprint? Is there
> first a CMYK to DeviceN LUT? And then there is a separate RGB to CMYK LUT?
> Is RGB is reached via concatenation of RGB-CMYK-DeviceN LUTs? Or is it a
> separately developed RGB-DeviceN LUT? What what is the basis for the RGB
> space? sRGB or other?
> Chris Murphy

I have only looked at the pro and prosumer Epsons; here I believe the
printer gets DeviceN, while GP accepts RGB and CMYK. The present drivers are
completely hand-tuned for each inkset and media and in fact the move to
color management was planned in order to alleviate the task of bringing up
new printers.



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