Re: [Gimp-developer] New Image/Color Management option

Elle Stone <ellestone ninedegreesbelow com> wrote:

On 05/20/2016 02:37 PM, Jason van Gumster wrote:

Elle Stone <ellestone ninedegreesbelow com> wrote:
I can't think of a single use case for trying to edit a non-color-manged
image in an ICC profile color-managed editing application such as GIMP.  

I think I can think of one: creating displacement/bump maps (often used as
textures in 3D graphics). Often in that case, pixel values aren't treated as
color, but a numeric non-color data (i.e. it's an instruction to displace
geometry---or other pixels---by this numeric mapping value).

But perhaps the artists that create these maps are not covered in the
audience specified in GIMP's vision statement.
In point of fact, the new GIMP color management options do NOT disable 
ICC profile color management.

If you want to disable color management, go into "Edit/Preferences/Color 
Management" and for "Image display mode" select "No color management".

Or you can achieve the same effect by assigning your monitor profile to 
the image file.

And that's all well and good, but either my ignorance is showing or this is
starting to sound like a case of semantics. I wasn't asking for the process of
how one might go about editing a non-color-managed image in a color-managed
application like GIMP. I was simply pointing out that there *is* at least one
use case for doing so.

As for the mechanics of actually doing this, you've pointed out a couple ways
to go about it (though disabling color management for the entire application
feels excessive). When working on these kinds of images---er, *maps*---aside
from numeric accuracy of the actual values, the priority when editing is being
able to see as much of the full range as possible, with even proportion between
values. To that end, temporarily assigning the monitor's color space to the map
is probably the best approach, I think.

That said, this does get me thinking and wondering a bit (though still
tangentially on-topic). A few GIMP filters such as Depth Merge, Lighting
Effects, Bump Map, and Displace rely on these kinds of maps. So technically,
you could have a color managed image that includes one or more of these maps on
separate layers. Ideally, it would be nice to be able to reliably edit those
layers as non-color maps without splitting them into different images with
their own independent "non"-color space.

How would you propose that GIMP handle color management in that case? In
Blender's compositor, for example, there's an option to explicitly set an input
image node to be interpreted as non-color data. Would it make sense to offer
that kind of option to individual layers in GIMP? If that doesn't make sense,
what's an alternative approach that *does*?



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