[argyllcms] Re: RGB Printer profiling and ColorSavvy CM2C

Alastair M. Robinson wrote:

At the moment, though, we can at least disable all our colour mangling, and with my own PhotoPrint application we can print images using an appropriate profile. On the strength of what you've told me over the last few days, I'll add "support for DeviceLink profiles" to the TODO list... 

I'm working on the project partly for my own satisfaction, and
partly on the basis it's easier to convince people with a working
example, than by merely "telling them so". The latter approach
understandably gets their backs up ...

Yes, the inclusion of the gamut mapping into the B2A processing is
fundamentally flawed, since it depends on the source gamut, which
is not actually connected with the output profile. There has been
some move to address this issue in ICC V4, but it still doesn't
cover it, since there is no defined PCS gamut (yet). Even
with this in place, I have my doubts about the quality loss
in concatenating two gamut mappings (input -> PCS, PCS -> output).


Yes, I see what you mean. Wouldn't the PCS gamut, by definition, be rather large though? 

It doesn't really change the problem, since the idea is that
the source gamut is contracted and expanded to the PCS gamut,
then the PCS gamut is contracted and possibly expanded to
the destination gamut. If the PCS gamut was a very large one,
and the source simply sat within it, then the destination
mapping would contract the whole colorspace (on the basis
of making the PCS gamut fit), reducing the colorfulness
of the result dramatically. The suggested standard PCS gamut
is a fairly large "printer like" one.

I haven't tried it yet, but I imagine that's a rather expensive operation, yes? 

Yes it takes some time (about the same time as generating one
of the B2A tables of a profile), but it's not so bad at medium
resolution on a modern GHz processor. The end result is noticeably
smoother and more accurate.

Graeme Gill.

Other related posts: