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

[Elle Stone <ellestone ninedegreesbelow com>]

On 05/12/2016 10:31 PM, Alexandre Prokoudine wrote:
> You are pretty much saying that it is wrong to force freedom of choice upon
> people. This doesn't make any sense.

Well certainly the current "Image/Color Management" options do offer 
users a lot of choices. But the same choices already were there in more 
sensible form with less potential for confusing and misleading the user.

Currently these are the choices in "Image/Color Management":

A. The user can leave the new "Enable Color Management" checked as it is 
by default.

B. The user can uncheck "Enable Color Management".

C. The user can assign a new profile, which includes the option to 
assign the built-in GIMP sRGB profile.

D. The user can convert the image to a new profile, which includes the 
option to convert the image to the GIMP sRGB profile.

E. The user can discard the image's profile, unless the image already is 
assigned the GIMP built-in sRGB profile, in which case this option is 
grayed out.

(The last option, to save the color profile to disk, literally saves the 
image's assigned profile to disk as an ICC profile, so isn't related to 
the above-listed options).

Option B seems to provide the user with the option to disable color 
management. But this is not what happens. The image is still color 
managed. It's still converted from the GIMP built-in sRGB profile to the 
user's chosen monitor profile. But if you set GIMP up to display the 
image ICC profile in the status bar, you'll see the words "not color 
managed". In other words, the status bar is lying to the user.

This "new freedom" provided by unchecking "Enable Color Management" 
seems to only be the freedom to internally assign the GIMP sRGB profile 
and at the same time be presented with misinformation about whether the 
image is actually still color managed.

But the user already has the freedom to assign the sRGB profile to an 
image by exercising Option C, which allows the user to assign a new 
profile, which already includes the option to assign the built-in GIMP 
sRGB profile even if it's the wrong profile for the image

And for non-sRGB images the user already has the freedom to assign the 
GIMP built-in sRGB profile by exercising Option E, which really ought to 
be relabelled as "Discard the currently assigned ICC profile and assign 
the GIMP built-in sRGB profile instead".

So can someone please explain to me what the utility of Options B and E, 
that isn't already covered by Option C????


Now let's see what really happens when the user exercises her freedom of 
choice and selects one of the "new freedoms" when she's opened a 
non-sRGB image.

For the sake of simplicity, let's assume the following:

1. The image is at "Perceptual gamma precision (sRGB) precision rather 
than "Linear light" precision.

2. The user has selected "Color managed display" in Preferences/Color 
Management.

3. The user chose a real monitor profile in Preferences, instead of 
choosing an sRGB ICC profile as the monitor profile. Let's also assume 
the user has chosen in Preferences to display the image's ICC profile on 
the image status bar.

4. The image is in the ArgyllCMS ClayRGB1998.icm (Adobe-compatible) 
color space. Let's also say this hypothetical image has some nice greens 
and blues that fall outside the very small sRGB color space gamut:

Before exercising her new freedom of choice, the status bar reads 
"Interchangeable with Adobe RGB (1998)" and the image is color-managed 
as usual, which is to say that the image is converted from the image's 
ICC profile (ClayRGB1998.icm) to the user's monitor profile as selected 
in Preferences.

If she now chooses option B and unchecks the option to "Enable Color 
Management", here's what happens:

1. The image appearance does in fact change. The image colors are now 
washed out because what unchecking "Enable Color Management" really does 
is *assign* the GIMP built-in sRGB profile to the image.

2. The status bar says "not color managed". But in fact the image really 
still is color managed because the image is still being converted from 
the assigned image profile to the monitor profile for display. The 
problem is that now the wrong ICC profile has been assigned. So the 
status bar is lying to the user, as can be ascertained by changing the 
Preferences/Color Management "Image display mode" to "No color management".

If the user really wants the freedom to assign the wrong ICC profile to 
an image, well, Option B isn't required as she already has this freedom 
from Option C, which allows the user to assign a new ICC profile, 
including the GIMP built-in sRGB profile, even if this is the wrong 
profile for the image.

Option E is just as bad as Option B. Option E says that it allows the 
user to discard the image's ICC profile, and if the image has any ICC 
profile other than the GIMP built-in sRGB profile, this option is 
available.

So if the user exercises her freedom to discard the image's ICC profile 
for the ClayRGB1998 image, what do you think happens?

Well, the image is immediately assigned the GIMP built-in sRGB profile. 
And for this particular image which is really a ClayRGB1998 (AdobeRGB 
compatible) image, the built-in sRGB profile is the wrong profile to 
assign, and so the colors look wrong.

So there is no "new freedom" being given to the user by the new option 
to uncheck "Enable Color Management". This option assigns the GIMP 
built-in sRGB profile to the image and then pretends that color 
management has been disabled, when in reality it hasn't been disabled.

And there's no "new freedom" being given to the user by the option to 
"Discard Color Profile", which option actually assigns the GIMP built-in 
sRGB profile.

So again, can someone please explain the utility of these new freedoms?

Also, whoever wants to write up GIMP documentation covering the new 
freedoms, please feel free to use the above descriptions of what really 
happens. I'll be happy to provide a hopefully complete set of cases that 
you'll need to cover.

Best,
Elle