[Openicc] New options on the mainline

[edmund ronald]

Why reinvent the wheel ? There are standard linearisation targets that
can be dumped in an image file, printed by Gutenprint, read by using
free (as in cost-free) software like Colorport  with ANY standard
instrument, Colorport or other manufacturer software generates a CGATS
file, and then that CGATS file can be easily parsed back into some
utility *which you need to write* to determine linearisation. The same
for profiling, one can assume that if the user can print his targets
(s)he can get the job done.

Doing it this way brings your job down to the reading of the linearity
values from a CGATS or txt file, which means a few hour work instead
of all this decision about what open source project to involve next. I
know about this stuff because I helped the Caldera guys integrate the
DTP70 instrument in their RIP,taking my DTP70 on location, and it took
us one afternoon to get it done.

Edmund



On Jan 20, 2008 10:19 PM, Hal V. Engel <hvengel at astound.net> wrote:
> On Sunday 20 January 2008 12:24:33 Kai-Uwe Behrmann wrote:
> > Am 20.01.08, 11:28 -0800 schrieb Hal V. Engel:
> snip
>
> > >
> > > When I looked at trying to linearize my printer a few weeks back what I
> > > wanted was to start with the existing curves and to be able to apply a
> > > correction to that curve.  The problem of course was the UI does not make
> > > that curve available and there was no way to get this without resorting
> > > to making API calls to the GutenPrint driver and even then it was not
> > > clear from the API docs that these calls are really what I wanted.
> >
> > We will see those task several times. As they are not Gutenprint specific,
> > it would make sense to handle them in a separate project. At the moment it
> > is unclear who takes over this task.
> >
> > > I think that what is really needed is an API that allows for applying a
> > > correction curve to the existing base curves.  I believe that this is how
> > > most RIPs operate but I really don't have any experience with them.  Once
> > > there was such an API exposing it in a UI so that users could hand enter
> > > a set of correction values would be a good starting place.  For example
> > > the QuadTone RIP Eye-One-ReadMe document shows a set of examples based on
> > > taking a set of measurements of a 21 step gray ramp (this is a B&W RIP)
> > > and then loading this into an application called QTR-Linearize-Data that
> > > analysis those measurements and gives a result something like:
> > >
> > > LINEARIZE="96.55 92.14 86.45 81.02 75.65 70.55 64.85 59.60 54.62 50.06
> > > 45.73 41.99 37.63 33.91 30.95 27.75 25.01 21.80 19.84 18.43 16.95"
> > >
> > > The user then takes this data and drops it into the QuadTone UI and tells
> > > it to use these measurements to correct the printers output.  The data
> > > above is nothing more than the L* values from the measurements.  We
> > > already have the tools to make similar sets of measurements and to create
> > > similar data sets. Of course the real issue is what would the GutenPrint
> > > API do with these measurements to make the linearization corrections?
> >
> > My impression is to keeping such stuff outside of Gutenprint makes
> > completely sense. The curves can easily described in ICC profiles. It
> > would be up to early colour binding applications or the print system to
> > select and chain the according profiles (calibration + final profile). We
> > could certainly assist in creating or teach in using the appropriate
> > tools.
>
> I was mostly trying to layout some "user" expectations in this specific area.
> That is a user would expect to be able to generate and print some type of
> linearization target that was correctly laid out for his/her
> spectrophotometer.  Then, either from the linearization software or
> externally, measure it and that this data would (after being entered into the
> linearization app if it were measured externally) result in the appropriate
> corrections being made to the ink curves.
>
> At first this could be very basic and could even be a set of command line apps
> to do a series of steps to get the job done.  For example, ArgllCMS could be
> used to generate and then measure the linearization targets.  The resulting
> CGATS measurement file could be used as input into the linearization app
> which would feed the resulting curves back into GutenPrint.  Once this was
> working we could start building a GUI around this and eventually end up with
> a nice fairly easy to use system.
>
> I do agree that this could be totally external to GutenPrint or it could also
> be part of GutenPrint or some combination of these.  From a user point of
> view where the separation takes place is not very important as long as things
> work.  But you are right that having this be external to GutenPrint would
> allow it to work with other drivers if those drivers exposed the needed
> interfaces.
>
> I also think these tool need to support the work that goes on when the
> GutenPrint team developes the initial set of ink curves.
>
> >
> > > Anyway I thought that I would through this out there to see if this sort
> > > of thing was possible.  I suspect that long term what it does should be
> > > based on some standard that tries to establish an ideal set of curves for
> > > each channel.  This might be based on something like G7.
> >
> > Would it make sense to you to support the provided G7 targets?
>
> I am not sure what you are asking.   But it would be possible to use LProf's
> SourceForge facilities such as CVS/SVN to support something like this.  It
> might even make sense to have this interface be an extension of LProf since
> it already has things like a UI for selecting and configuring meters and
> longer term LProf will have facilities for generating and reading printer
> targets.  Currently we are focused on display calibration and profiling work.
> But I don't think we can take this on unless there are new volunteers who can
> take on the added work load and I think that we would need someone to take on
> the lead role for this effort as well.
>
> Hal
>
> _______________________________________________
> openicc mailing list
> openicc at lists.freedesktop.org
> http://lists.freedesktop.org/mailman/listinfo/openicc
>