Roger,
I don't like the idea of just decreasing the saturation at least from a
numerical perspective. From what I've read we are not that good at
discerning colors, it takes serious effort on our part and practically
laboratory conditions to discern colors with less than 2-5 DE?? of
difference. If this is right, just changing saturation would probably
not result in optimal result especially at low L* for example. It maybe
a "shorter" path to increase L* then to vary a* and b* such as to vary
only the saturation. This should be especially true if the shortest path
also provide a less discernible color difference, doesn't it?
As for PS you could be right I don't know but it could be also because
the printer profile doesn't provide the 2 rendering intent tables?
Yves
On 11/25/2019 10:17 AM, graxx@xxxxxxxxxxxx wrote:
Yves,
How does Argyll do Perceptual Intent?
I have not read anything about that. It's probably in Argyll documentation?
But, in general, it's a matter of decreasing saturation to move the out of
gamut colors inside the Destination gamut, presumably preserving the original
hue angle, but there's a whole science in how to do this, and not all
profilers do it the same. Some move greens further in, others move reds further
in and so on. Many will use a decreasing saturation function in that, only out
of gamut colors will be progressively desaturated at the gamut's edge. Others
will apply a wholesale desaturation, decreasing all Source colors so that they
fit inside the Destination gamut. There's a lot of good papers out there on how
this is done. But there's nothing like finding it out for yourself empirically.
It's not hard to analyze but it's time consuming, without some kinds of
analytical tools.
Take Photoshop. Photoshop is easy because there is no difference between their Perceptual
and Colorimetric intents -- to make their lives easier and to avoid users calling them on
the telephone to complain about the "difference".
/ Roger
-----Original Message-----
From: argyllcms-bounce@xxxxxxxxxxxxx <argyllcms-bounce@xxxxxxxxxxxxx> On Behalf
Of Yves Gauvreau
Sent: Monday, November 25, 2019 9:17 AM
To: argyllcms@xxxxxxxxxxxxx
Subject: [argyllcms] Re: Rendering intent?
Roger,
this would mean that "perceptual" as a different meaning depending on which
tool you use, right? How Argyllcms does this?
Is the same true for Relative colorimetric? Is only a change in saturation
considered with the relative intent or something else?
My understanding of a color is that it is defined by a point in some 3 dimensional colorspace and
if you have to move it around and you limit yourself to only changing saturation your giving up 2
other potential options. I would have thought the most recent "distance" metrics or even
the simple euclidean distance to be more appropriate then just shifting the saturation as seems to
be the case in the various docs I've seen. I know I may not have seen the "right" one.
That's why I ask.
On 11/25/2019 8:23 AM, graxx@xxxxxxxxxxxx wrote:
Every profiler I know does the Perceptual intent *differently*.
It's considered their "secret sauce".
/ Roger
-----Original Message-----
From: argyllcms-bounce@xxxxxxxxxxxxx <argyllcms-bounce@xxxxxxxxxxxxx>
On Behalf Of Yves Gauvreau
Sent: Monday, November 25, 2019 8:21 AM
To: argyllcms@xxxxxxxxxxxxx
Subject: [argyllcms] Rendering intent?
Hi,
I'm curious, every time I read some doc on how relative colorimetric
and perceptual intent works, it seems as if it only a saturation (2D)
change is considered, why not the shortest distance (3D) to the gamut
boundary of the destination space?
Can you direct me to something that would explain how Argyllcms does this.
Thanks,
Yves
