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

On 05/12/2016 03:56 PM, Michael Natterer wrote:
The option in Image -> New allows to disable color management
and whatever color management transforms on a per-image base.

What specifically is included in "color management transforms"?

This is mainly because almost nobody understands what this
whole color stuff is about at all.

There is a difference between a deep theoretical understanding and a working understanding.

Here is everything a user needs for a basic working understanding of color management:

1. Make or find an accurate monitor profile. Select that profile in Preferences. In a worst-case scenario, set the monitor to the manufacturer-supplied sRGB preset and use sRGB as the monitor profile.

2. Open an image. If there's no embedded ICC profile, assign the right profile. For many (but not all) untagged images, sRGB is the right choice.

3. Convert the image to the user's chosen RGB working space.
Sadly, in GIMP the RGB working space must be sRGB, or else too many editing operations won't work because of the hard-coded sRGB parameters in the code base.

4. When you are done editing, convert the image to the desired output color space, which for the web should be sRGB.

All (sic!) graphics artists
I know and have asked switch off color management entirely
in Photoshop because it's this confusing thing that changes
colors in an unpredictable way  (which is not surprising
given the cluelessness).

Well, see, PhotoShop doesn't actually provide an option to disable color management.

Under "Color Management Policies" there are several options, one of which is "Off". But choosing "Off" doesn't do what you might think it does. Instead, quoting from an Adobe forum post (

""Off" is an illusion, it's not really off. What happens is that the working space is assigned to the file no matter what color space the file was created in . . . And to top it off, the file is then saved without an icc profile, throwing everything completely to the wind even if it wasn't before."

I left out part of the quote because it was addressing an issue with a broken monitor profile, so see the forum post for the full quote.

What is said in the forum post coheres with what I remember to be the case for CS2.

So your confused PhotoShop users are just making a bad situation worse.

There used to be an option in PhotoShop to disable color management for *printing*. This option was very useful in advanced printing workflows. This option was removed to the great dismay of people trying to make and use custom print profiles with PhotoShop. But this is not what you are talking about.

There also has been much gnashing of teeth over the years among PhotoShop users trying to make CMYK files for printing. But this particular color management issue has nothing to do with GIMP, because GIMP doesn't support CMYK.

The sane choice way to let users disable it, rather than
forcing it upon them.

If you want to let users disable color management on a per image basis, then the per image option should do exactly what the global option in "Preferences/Color Management/Image display mode/No color management" does, which is "Send the RGB values directly to the screen without doing any conversion from the image profile to the monitor profile for display".

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.


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