[Openicc] GoSoC 2011: CPD and Color Management

Robert Krawitz rlk at alum.mit.edu
Wed May 4 17:13:14 PDT 2011

On Wed, 4 May 2011 07:55:54 -0400, Robert Krawitz wrote:
> On Wed, 4 May 2011 05:40:49 +0200, edmund ronald wrote:
>> Robert,
>> Do you also distinguish Graeme's states 1,2,3 below in this way for
>> Gutenprint? Or would you place the boundaries differently?
> This more or less matches my own process for tuning a printer: I first
> get the drop sizes right, then the light/dark channels ("channel
> splitting", in my terminology), then gamma and level adjustments.

Actually, there's one step that's missing: generating additional
colors (such as the red and blue on the Epson R1800) and auxiliary
channels (such as the gloss optimizer on same).

>> On Wed, May 4, 2011 at 3:52 AM, Graeme Gill <graeme at argyllcms.com> wrote:
>>> edmund ronald wrote:
>>>>  However I do think ink settings ALSO need to be able to exist without
>>>> the profile since the ink settings precede the profile, and since it
>>>> is extremely advantageous to be able to adopt the ink settings from
>>>> some known paper as a quick starting point to work with another paper.
>>>> Ink settings, as we agree do precede profiles, and therefore need to
>>>> be able to exist and be invoked independently of profiles.
>>> Yes. Such a format is needed anyway, to communicate the settings
>>> between the print system and the user and or profiling software,
>>> so that they can be embedded in the profile.
>>> Note that a print system mechanism to enable or disable calibration
>>> and separation is also needed to support print calibration.
>>> In general for something like an inkjet printer with light & dark inks
>>> there are four (reasonably distinct) printer states:
>> 1)
>>> * raw with setting adjustments:
>>>    Raw response of the physical color channels. There are still
>>>    resolution, dot size and screening settings, plus a
>>>    range setting (maximum per color value) involved.
>>>    This state is used so as to be able to determine these settings,
>>>    as well as determine the light and dark channel crossovers.
>> 2)
>>> * separated and adjusted
>>>    The dot level settings are set, and the light and dark channels
>>>    have been combined and crossed over to create the set of
>>>    logical device color channels. There are settings and/or tables
>>>    that have been created to do this.
>>>    This state is used to create calibration curved.
>> 3)
>>> * calibrated, separated and adjusted
>>>    The logical device color channels have had calibration
>>>    curves applied to them.
>>>    This state is used to create profiles.
>> 4)
>>> * Profiled, calibrated, separated and adjusted
>>>    The device ICC profile is used to convert incoming
>>>    colorspaces to the devices colorspace.
>>>    This state is the normal end user printing state.
>>> To setup a printer, you need access to all of these states, not just
>>> profiled/not profiled.
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