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

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


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.


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?


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