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

Robert Krawitz rlk at alum.mit.edu
Wed May 18 18:27:10 PDT 2011

On Wed, 18 May 2011 18:55:47 -0600, Chris Murphy wrote:
> On May 18, 2011, at 6:49 PM, Robert Krawitz wrote:
>> On Wed, 18 May 2011 18:40:37 -0600, Chris Murphy wrote:
>>> On May 18, 2011, at 6:18 PM, Robert Krawitz wrote:
>>> But in any even ColourBase is UK only, not available in the U.S.
>> Which makes me suspect that whatever it is isn't stored in the printer
>> at all, but on the host.
> For ColourBase yes its possible, I have no idea what this beast is
> or does really. But even if it stores on the host, it would also
> need to store something on the printer also in order to prevent
> different workstations from producing different output to the same
> printer.

If anything's stored on the printer -- and we're only making that
assumption -- I believe it's a profile of some kind, and has nothing
directly to do with drop sizes.

My understanding is that the closed-source component that's available
for licensing is a halftone module, not a color module.  At least,
that's what it's called, and that's consistent with this trick,
whatever it is, only working with the OEM driver.

Why?  Well, other drivers using the halftone module presumably have
their own color transforms.  If they were using the OEM color module,
what could they offer that Epson doesn't?  Certainly not CMYK, for
instance.  And some of the third party RIPs, like Jon Cone's
Piezography (does that still exist?), use custom inksets, which
obviously the Epson color module can't do anything useful with.  Color
transforms have to be done above the halftone module, since the
halftone module doesn't understand at a high level what someone else's
color module is trying to do.

If it were drop sizes that were stored, the halftone module *could*
make use of them (barring different viscosity or vapor pressure
characteristics of third party inks -- but those could cause a lot of
problems for the printer regardless).  While Epson likes selling its
own inks, it also likes selling printers (particularly high end ones),
and there would be no obvious reason for its own halftone module not
to make use of them, especially since it would just be a binary blob
from the printer.

Ergo, what makes sense is that if anything is stored in the printer,
it's a profile that's useful for color transforms (and therefore *not*
useful for non-OEM color transforms using an OEM halftone module) but
not for halftoning.

I suspect that even if we could get hold of that data and interpret
it, it wouldn't be very useful for Gutenprint, since our color
transforms are likely very different from Epson's.

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