Re: [Gimp-developer] Soft proofing and the GIMP Display Filters and Color Management settings

[Elle Stone <ellestone ninedegreesbelow com>]

On 03/03/2014 03:16 AM, Alexandre Prokoudine wrote:
> 02 марта 2014 г. 21:46 пользователь "Elle Stone" <
> ellestone ninedegreesbelow com> написал:
>
> > 4. The Color Proof display filter should include the option to enable and
> disable marking out of gamut colors, overriding any choice made in
> "Preferences/Color Management".
>
> IMO, it's worth having a look how much we can salvage from
> http://registry.gimp.org/node/24944.
>
> Alexandre

I downloaded the Color Management+ display filter plugin code. It does 
use lcms1. So I'm reading through the CM+ code and the LCMS2 
documentation, the goal being to match LCMS2 functions up with the lcms1 
functions used by the the plugin.

Soft proofing of course is used for more than just converting an RGB 
image to a CMYK color space. But probably the very useful CM+ plugin 
features (gray scale channel displays, for example) could be generalized.

On 03/05/2014 04:26 AM, Omari Stephens wrote:
> First and foremost, it's nice to see someone working on GIMP color
> management again, so yay :o)

The odd behavior of the display filters came to my attention because 
I've been working on rewriting some of the GIMP color management 
documentation and so took a closer look at what all the display filters do.

As the display filters currently can be used to do strange and 
completely wrong things, it seemed better to try to fix the filters than 
write documentation about what not to do when using them! Feedback, 
requests, observations, etc are very welcome. I'll collect everything 
into a bug report/enhancement request and also keep looking at the code 
to see where/how to make changes.

> All of the suggestions seem reasonable for me.  That said, additionally,
> I think it'd be really useful to be able to enable or disable
> soft-proofing quickly.  It would be independently useful to be able to
> enable or disable out-of-gamut color marking quickly.
>
> The usecase here is that, suppose I'm working up an image for print.
> Let's say I want to adjust the curves of the image so that I get a
> reasonable amount of shadow detail, but not so much that I get shadow
> banding (as from running out of dynamic range in the shadows).  I'll
> want out-of-gamut colors enabled in order to judge how much shadow
> detail will actually show up in print.  But I'll want it _disabled_ to
> judge banding, since the contrasting "out-of-gamut" color tends to make
> gradients really difficult to evaluate.
>
> --xsdg
>    doppler-photo.net

I agree 100% that soft proofing requires the ability to quickly switch 
gamut checks on and off, and also quickly enable/disable soft proofing.

Another question:

A common way to soft proof requires having the image open twice to 
compare the original with the soft proofed version.

The current GIMP preferences allow you to choose "Print Simulation" in 
"Preferences/Color Management/Mode of operation". But that sets *all* 
open images to Print Simulation mode, for which I can't think of any use 
cases.

So perhaps the option to choose Print Simulation mode should be removed 
from "Preferences/Color Management/Mode of operation", but leave the 
ability to choose soft proofing presets for those people who routinely 
softproof to a particular output profile. Any thoughts? Does anyone have 
an actual use case for putting all open images in Printer Simulation mode?


Elle