Re: [Gimp-developer] Color management dataflow [was: Color management (UI perspective for GIMP 2.8)]

2010-02-13 Thread Graeme Gill
Christopher Curtis wrote:
> On a more philosophical note, how does one represent a color that does
> not exist on a display but does on an output device?  Do we make the
> assumption that the display always has the widest gamut?  (I.e: GIMP
> will never run on a mono/CGA device and print to a CMYK printer.)  Is
> that a concern?

There's nothing special about this. In general any transformation
from one colorspace to another has to cope with different gamuts.
You simply choose how to handle it (ie. clip, perceptually map, etc.)
by choosing an intent.

It's not unknown to have a mode in an image editor that compresses the
gamut of the source so that a very large gamut image can be viewed
on a limited gamut display without loosing the ability to be able
to see all its color variations. Naturally it will look a lot
duller than it will when displayed on the intended device.

Graeme Gill.
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Re: [Gimp-developer] Color management dataflow [was: Color management (UI perspective for GIMP 2.8)]

2010-02-13 Thread Graeme Gill
David Gowers wrote:
> Imo the video card is the correct handler of these issues. X should
> just upload an appropriate lookup table (which is functionality
> already available in X, but doesn't happen automatically). Presumably
> a multihead video card allows multiple LUTs. From that point of view,
> it might make most sense for the desktop environment to do the
> uploading of the LUT(s), since you would probably use it to select and
> test the profile.

Calibration != Profiling

While most cards have per channel Luts, none will have
per rendering context 3D color transforms (although it
can be simulated using 3D texture lookups). Rendering
context is usually somewhere up the rendering stack though,
not something the hardware will be directly aware of.
(It's rendering context because the transform depends on
the source colorspace & intent as well as the display
profile. In general it's not a 3x3 matrix transform either.)

Graeme Gill.
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Re: [Gimp-developer] Color management dataflow [was: Color management (UI perspective for GIMP 2.8)]

2010-02-13 Thread David Gowers
On Sun, Feb 14, 2010 at 10:03 AM, Christopher Curtis  wrote:
> On Sat, Feb 13, 2010 at 5:58 PM, Jon Cruz  wrote:
>
> [...]
>> does seem to come down to the points that X11 does not and should not deal
>> with color management in these regards and needs to leave it to the
>> individual apps. To get a fully usable system, X11 would require some major
>> reworking, and thus won't be seen any time soon.
>
> Do you have a reference to these discussions?  It seems like X
> *should*, accepting that it may be difficult.

Imo the video card is the correct handler of these issues. X should
just upload an appropriate lookup table (which is functionality
already available in X, but doesn't happen automatically). Presumably
a multihead video card allows multiple LUTs. From that point of view,
it might make most sense for the desktop environment to do the
uploading of the LUT(s), since you would probably use it to select and
test the profile.

>> Of course, to end up with an optimal workflow for end users, GTK could be
>> adapted to handle a fair bit by itself (and, yes, there is work happening on
>> this at the moment). Toolbars, icons, menus, color selectors, [...]
>
> I was just going to say here that putting it in GTK could also 'fix'
> the color selector issues; let me just emphasize that point here.
>
>
> On a more philosophical note, how does one represent a color that does
> not exist on a display but does on an output device?
> Do we make the
> assumption that the display always has the widest gamut?

That's tempting but ultimately incorrect, IMO,
since most displays approximate sRGB, which only has what ..56%
coverage of the visible spectrum? We should only make that assumption
when the coverage becomes close to a superset of all other important
mediums of reproduction (eg. when scRGB or whatever displays with 90%
coverage of visible gamut are common).

Looking at GEGL, the intermediate result of a computation (like
mathematically a + b where a,b are layers) may be >1.0 or <0.0, and we
must be able to differentiate  those areas ,in the image and when we
are eyedropping.
I guess we need some way of depicting exposure stops independently for
the R,G,B levels and also of  setting them.

To clarify: I mean that the color RGB 1.0, 1.0, 1.0 would have
exposure 0,0,0; the color RGB -1.,0.,-2. would have exposure -1, 0,
-2; RGB 2,2.5,2.8 would have exposure 1, 2, 2 etc.
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Re: [Gimp-developer] Color management dataflow [was: Color management (UI perspective for GIMP 2.8)]

2010-02-13 Thread Christopher Curtis
On Sat, Feb 13, 2010 at 5:58 PM, Jon Cruz  wrote:

[...]
> does seem to come down to the points that X11 does not and should not deal
> with color management in these regards and needs to leave it to the
> individual apps. To get a fully usable system, X11 would require some major
> reworking, and thus won't be seen any time soon.

Do you have a reference to these discussions?  It seems like X
*should*, accepting that it may be difficult.

> Of course, to end up with an optimal workflow for end users, GTK could be
> adapted to handle a fair bit by itself (and, yes, there is work happening on
> this at the moment). Toolbars, icons, menus, color selectors, [...]

I was just going to say here that putting it in GTK could also 'fix'
the color selector issues; let me just emphasize that point here.


On a more philosophical note, how does one represent a color that does
not exist on a display but does on an output device?  Do we make the
assumption that the display always has the widest gamut?  (I.e: GIMP
will never run on a mono/CGA device and print to a CMYK printer.)  Is
that a concern?

Chris
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Re: [Gimp-developer] Color management dataflow [was: Color management (UI perspective for GIMP 2.8)]

2010-02-13 Thread Jon Cruz

On Feb 13, 2010, at 12:08 AM, David Gowers wrote:

> I agree; GIMP windows should support color management for individual
> image windows according to these atoms, absolutely;
> What it would be of little use to do, is to support showing the SAME
> image in a single window spanning multiple monitors, with different
> colormanagement for each monitor-segment of that Single window.
> As I understand, that is what Christopher was requesting and yahvuu
> was accurately describing as an uncommon use case, rather than the
> general case of one image window on this monitor, one on that, and
> they are color managed differently because of it.

Ah, but that is exactly what I was thinking. I know the ancient-of-days 
workflow was to have one "good" color monitor for the actual images, and a 
monochrome "control" monitor with the buttons and interfaces to control the 
software. Over the years I've seen more and more users with two or three good 
monitors, including gamers and programmers in addition to artists. And I have 
seen such users have windows with images spanning those monitors very often.

I'd also point out that this single-window-across-multiple-monitors use case is 
exactly one of the main ones that artists using Macintoshes had been quite fond 
of pointing out to their "poor cousins" on Windows (when I've seen them do 
such, it reminds me very much how "real programmers" use Linux). It highlights 
the fact that MacOS has had good color management built in to the OS for years 
and years.
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Re: [Gimp-developer] Color management dataflow [was: Color management (UI perspective for GIMP 2.8)]

2010-02-13 Thread Jon Cruz

On Feb 13, 2010, at 2:39 AM, yahvuu wrote:

> 
> In reality, the wall of monitors probably won't work like that as long
> as GIMP has to manage the windows' colors. As others have said, it is
> unreasonable to manage split windows at application level.

Well, personally I don't consider it unmanageable at all to have an application 
manage split windows. Especially with all the detail being presented via GTK on 
the geometry and positioning of the monitors, this is a fairly trivial matter. 
That's trivial in the abstract case, of course. The main complication will be 
in the details of hooking GIMP's display code at the very last moment (since 
among other things color management adjustments need to be done once and only 
once and on the final result just before it gets sent to the display).
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Re: [Gimp-developer] Color management dataflow [was: Color management (UI perspective for GIMP 2.8)]

2010-02-13 Thread Jon Cruz

On Feb 13, 2010, at 9:42 AM, Hal V. Engel wrote:

> I some ways I agree with Chris but the X.Org developers have insisted on an 
> ongoing basis that it is NOT their responsibility to handle color management 
> of the display.   If we wait for X.Org to implement CM it will likely never 
> happen.

I'd definitely second this point. I've been in many discussions with several 
key players in this arena, and when all technical details are explored it does 
seem to come down to the points that X11 does not and should not deal with 
color management in these regards and needs to leave it to the individual apps. 
To get a fully usable system, X11 would require some major reworking, and thus 
won't be seen any time soon.

Of course, to end up with an optimal workflow for end users, GTK could be 
adapted to handle a fair bit by itself (and, yes, there is work happening on 
this at the moment). Toolbars, icons, menus, color selectors, etc., ideally 
would be color managed by GTK. But whatever "automatic" color management is 
added to GTK needs to be done in such a way as to allow the "smart" programs 
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Re: [Gimp-developer] Color management dataflow [was: Color management (UI perspective for GIMP 2.8)]

2010-02-13 Thread Hal V. Engel
On Saturday 13 February 2010 09:15:13 am Christopher Curtis wrote:
> On Sat, Feb 13, 2010 at 5:39 AM, yahvuu  wrote:
> > Christopher Curtis wrote:
> >> What happens in a multi-head setup when I maximize an image over (say)
> >> a CRT and an LCD?  Does "monitor profile" take this into account?
> >
> > Following the logic of the diagram, i'd say yes:
> > your case is equivalent to cutting an image into two pieces and printing
> > one piece with an ink jet and the other one with a laser printer.
> 
> I don't know that I'd agree with that; the example was not meant as a
> use-case, just a demonstration of a potential problem.  One could
> argue that you'd need to print exactly this way to take advantage of
> the specific gamuts (or materials) of each device.
> 
> But that's not my point.  I would rather suggest this:  that GIMP not
> do colorspace management of the display profile at all, and rely on X
> to do the right thing even if it does not do so today.
> 
> Imagine you are editing some image on one screen and trying to match
> another image opened in another program on a different head.  This
> other program is not colorspace aware because it's scientific modeling
> data or whatever so you have this dichotomy.  In reality, you may
> never be able to match the colors because of the different display
> device gamuts.  Maybe you can work around this with 'Acquire Image ->
> Screen Shot' but isn't that really too burdensome?
> 
> You could push colorspace management into GTK, which would be better,
> but at the end of the day only one thing should be transforming gamuts
> and I think that thing is X.  Perhaps GTK and X can negotiate who's in
> control so it becomes optional at the GTK level, but then you have the
> possibility that the transformations are implemented differently and
> slightly incompatibly.  I think it's better to fix the problem once
> and to do so in a way that all applications can take advantage of it.
> 
> It is X's job to render the final display, whether it's local, remote,
> DPS, Xprt, or whatever else X can render to.
> 
> $0.02
> Chris

I some ways I agree with Chris but the X.Org developers have insisted on an 
ongoing basis that it is NOT their responsibility to handle color management 
of the display.   If we wait for X.Org to implement CM it will likely never 
happen.

Hal
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Re: [Gimp-developer] Color management dataflow [was: Color management (UI perspective for GIMP 2.8)]

2010-02-13 Thread Christopher Curtis
On Sat, Feb 13, 2010 at 5:39 AM, yahvuu  wrote:
> Christopher Curtis wrote:
>> What happens in a multi-head setup when I maximize an image over (say)
>> a CRT and an LCD?  Does "monitor profile" take this into account?
>
> Following the logic of the diagram, i'd say yes:
> your case is equivalent to cutting an image into two pieces and printing
> one piece with an ink jet and the other one with a laser printer.

I don't know that I'd agree with that; the example was not meant as a
use-case, just a demonstration of a potential problem.  One could
argue that you'd need to print exactly this way to take advantage of
the specific gamuts (or materials) of each device.

But that's not my point.  I would rather suggest this:  that GIMP not
do colorspace management of the display profile at all, and rely on X
to do the right thing even if it does not do so today.

Imagine you are editing some image on one screen and trying to match
another image opened in another program on a different head.  This
other program is not colorspace aware because it's scientific modeling
data or whatever so you have this dichotomy.  In reality, you may
never be able to match the colors because of the different display
device gamuts.  Maybe you can work around this with 'Acquire Image ->
Screen Shot' but isn't that really too burdensome?

You could push colorspace management into GTK, which would be better,
but at the end of the day only one thing should be transforming gamuts
and I think that thing is X.  Perhaps GTK and X can negotiate who's in
control so it becomes optional at the GTK level, but then you have the
possibility that the transformations are implemented differently and
slightly incompatibly.  I think it's better to fix the problem once
and to do so in a way that all applications can take advantage of it.

It is X's job to render the final display, whether it's local, remote,
DPS, Xprt, or whatever else X can render to.

$0.02
Chris
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Re: [Gimp-developer] Color management dataflow [was: Color management (UI perspective for GIMP 2.8)]

2010-02-13 Thread yahvuu
Christopher Curtis wrote:
> What happens in a multi-head setup when I maximize an image over (say)
> a CRT and an LCD?  Does "monitor profile" take this into account?

Following the logic of the diagram, i'd say yes:
your case is equivalent to cutting an image into two pieces and printing
one piece with an ink jet and the other one with a laser printer.

In reality, the wall of monitors probably won't work like that as long
as GIMP has to manage the windows' colors. As others have said, it is
unreasonable to manage split windows at application level.

However, in those places where color is really important,
a second monitor means additional calibration cost
and an additional potential source of error, i guess.


regards,
yahvuu

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Re: [Gimp-developer] Color management dataflow [was: Color management (UI perspective for GIMP 2.8)]

2010-02-13 Thread David Gowers
On Sat, Feb 13, 2010 at 5:22 PM, Jon Cruz  wrote:
> However, the answer to the base question is "Yes, X and Gtk support that to
> a very good degree, and all the low-level API's support delivering all the
> required information".
> and "No, X does nothing with the colorspaces. It is left to the application
> to implement"
> It also is more of a per-monitor issue, rather than per-pixel. So one
> generally will have to deal with a small set of rectangles (two being the
> most common) to adjust. So it's not *quite* up to the complexity of a purely
> per-pixel problem.
> I also would question the assertion that it is an uncommon use case. Those
> most likely to be working seriously with images are generally much likely to
> have two (or more) monitors. They also have a higher chance of caring about
> color fidelity.

I agree; GIMP windows should support color management for individual
image windows according to these atoms, absolutely;
What it would be of little use to do, is to support showing the SAME
image in a single window spanning multiple monitors, with different
colormanagement for each monitor-segment of that Single window.
As I understand, that is what Christopher was requesting and yahvuu
was accurately describing as an uncommon use case, rather than the
general case of one image window on this monitor, one on that, and
they are color managed differently because of it.
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Re: [Gimp-developer] Color management dataflow [was: Color management (UI perspective for GIMP 2.8)]

2010-02-12 Thread Jon Cruz

On Feb 12, 2010, at 5:42 PM, Omari Stephens wrote:

> On 02/12/2010 10:12 PM, Christopher Curtis wrote:
>> On Fri, Feb 12, 2010 at 11:55 AM, yahvuu  wrote:
>> 
>>> here are some diagrams depicting selected configurations for 
>>> colormanagement:
>>> http://yahvuu.files.wordpress.com/2009/08/dataflow.png
>> 
>> What happens in a multi-head setup when I maximize an image over (say)
>> a CRT and an LCD?  Does "monitor profile" take this into account?
>> 
>> I think my question is: Is X handling the colorspace or are profiles
>> being applied on individual pixel regions?  Is this even supported or
>> is there something else I'm not understanding at a very basic level?
> 
> This is an uncommon usecase that would require too much effort to 
> support properly for the small amount of benefit.
> 
> X11 has an atom which stores one ICC display profile per screen.  We 
> would have to change the display transform depending on which screen 
> each pixel shows up on.  This would also mean that we'd have to deal 
> with the case where an image tile is split across two screens.
> 
> Again, this would be a lot of code (and, thus, the potential for a lot 
> of bugs).  It would be infrequently used (and so the bugs would tend to 
> not be found as quickly).  And it would likely slow down our common code 
> paths for little benefit.

However, the answer to the base question is "Yes, X and Gtk support that to a 
very good degree, and all the low-level API's support delivering all the 
required information".

and "No, X does nothing with the colorspaces. It is left to the application to 
implement"

It also is more of a per-monitor issue, rather than per-pixel. So one generally 
will have to deal with a small set of rectangles (two being the most common) to 
adjust. So it's not *quite* up to the complexity of a purely per-pixel problem.

I also would question the assertion that it is an uncommon use case. Those most 
likely to be working seriously with images are generally much likely to have 
two (or more) monitors. They also have a higher chance of caring about color 
fidelity. And given the direction GIMP is taking in regards to dropping support 
for the casual users (or whichever wording best describes the current directive 
on this) I would expect this to be even more in line with GIMP's targeted user 
base and use cases.

Of course, I've not delved down into the details of GIMP's display code and 
where to best hook in such display transformations. On the other hand, when I 
added the initial XICC X11 profile support to Inkscape I had researched this a 
fair bit, and for Inkscape's display code the extra needed for multi-monitor 
support is actually rather trivial.

Then again the main consideration does need to go to the pragmatic factors. 
Given the constraints of that situation (including being the sole engineer 
doing any and all color work), per-monitor simultaneous profile support was 
deferred. However, switching profiles as the window moved mainly from one 
monitor to the next went in, along with dynamic detection and reloading of the 
profile as they get set or cleared on the current monitor also went in quite 
easily.

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Re: [Gimp-developer] Color management dataflow [was: Color management (UI perspective for GIMP 2.8)]

2010-02-12 Thread Omari Stephens
On 02/12/2010 10:12 PM, Christopher Curtis wrote:
> On Fri, Feb 12, 2010 at 11:55 AM, yahvuu  wrote:
>
>> here are some diagrams depicting selected configurations for colormanagement:
>> http://yahvuu.files.wordpress.com/2009/08/dataflow.png
>
> What happens in a multi-head setup when I maximize an image over (say)
> a CRT and an LCD?  Does "monitor profile" take this into account?
>
> I think my question is: Is X handling the colorspace or are profiles
> being applied on individual pixel regions?  Is this even supported or
> is there something else I'm not understanding at a very basic level?

This is an uncommon usecase that would require too much effort to 
support properly for the small amount of benefit.

X11 has an atom which stores one ICC display profile per screen.  We 
would have to change the display transform depending on which screen 
each pixel shows up on.  This would also mean that we'd have to deal 
with the case where an image tile is split across two screens.

Again, this would be a lot of code (and, thus, the potential for a lot 
of bugs).  It would be infrequently used (and so the bugs would tend to 
not be found as quickly).  And it would likely slow down our common code 
paths for little benefit.

--xsdg
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Re: [Gimp-developer] Color management dataflow [was: Color management (UI perspective for GIMP 2.8)]

2010-02-12 Thread Christopher Curtis
On Fri, Feb 12, 2010 at 11:55 AM, yahvuu  wrote:

> here are some diagrams depicting selected configurations for colormanagement:
> http://yahvuu.files.wordpress.com/2009/08/dataflow.png

What happens in a multi-head setup when I maximize an image over (say)
a CRT and an LCD?  Does "monitor profile" take this into account?

I think my question is: Is X handling the colorspace or are profiles
being applied on individual pixel regions?  Is this even supported or
is there something else I'm not understanding at a very basic level?

Thanks,
Chris
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Re: [Gimp-developer] Color management dataflow [was: Color management (UI perspective for GIMP 2.8)]

2010-02-12 Thread Martin Nordholts
On 02/12/2010 07:18 PM, Omari Stephens wrote:
> If the user with a weird monitor (wide-gamut, AdobeRGB, or other) has a
> display profile and opens an image-without-profile, what do we display?
>We can't apply the display profile unless the image has some source
> color profile to link to the transform.

This is where I suggest we use the working space color profile, although 
always using sRGB would work too in the scope of this discussion. Yes, 
in order to display the image we need to assume a color color profile, 
but the way I think this is different from thinking about the image as 
having an implicit color profile.


> In doing so, it allows us to stop special-casing for cases where the
> image may not have a color profile.  We gain uniformity of display logic
 > and a decrease in code complexity by being able to assume the presence
 > of a color profile as an invariant.

We need special casing either way, it's just a matter of where we have 
it. With your implicit profile strategy, we need a special case in the 
export code and image property code:

   if image.color_profile_implicit()
 color_profile = null
   else
 color_profile = image.get_color_profile()

while with my strategy it would be in the display code:

   color_profile = image.get_color_profile()
   if (color_profile == null)
 color_profile = gimp.get_working_space_color_profile()

Since we want to support working with non-color managed images it is 
more logical to handle images with no associated color profile than to 
handle images with implicit color profiles.

"Images always have an associated color profile" is by design not an 
invariant.


Regards,
Martin
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Re: [Gimp-developer] Color management dataflow [was: Color management (UI perspective for GIMP 2.8)]

2010-02-12 Thread Omari Stephens
On 02/12/2010 05:36 PM, Martin Nordholts wrote:
> On 02/12/2010 06:27 PM, Omari Stephens wrote:
>> On 02/12/2010 04:55 PM, yahvuu wrote:
>>> Hi,
>>>
>>> here are some diagrams depicting selected configurations for 
>>> colormanagement:
>>> http://yahvuu.files.wordpress.com/2009/08/dataflow.png
>>
>> I believe number 1 is incorrect:
>> All images in GIMP will have a color profile.
>
> People will want to create unmanaged images without a color profile for
> use on the web for example, so we need to handle images with no color
> profile attached. I think introducing the conepts of "implicit profiles"
> adds unnecessary complexity.

If the user with a weird monitor (wide-gamut, AdobeRGB, or other) has a 
display profile and opens an image-without-profile, what do we display? 
  We can't apply the display profile unless the image has some source 
color profile to link to the transform.  Hence, we assume sRGB to enable 
this and other situations to behave as correctly as possible.  The sRGB 
assumption is one what we already make, this change will simply make 
that assumption a bit more explicit.

In doing so, it allows us to stop special-casing for cases where the 
image may not have a color profile.  We gain uniformity of display logic 
and a decrease in code complexity by being able to assume the presence 
of a color profile as an invariant.

And the code itself is trivial: just add a "give_me_color_profile" 
function which returns icc-profile contents if present, or the sRGB 
profile otherwise.  (with a more-reasonable name, of course).

--xsdg
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Re: [Gimp-developer] Color management dataflow [was: Color management (UI perspective for GIMP 2.8)]

2010-02-12 Thread yahvuu
hi, and thanks for the feedback


Omari Stephens wrote:
> I believe number 1 is incorrect:

First thing to note is that i should have added a legend:
  - grey:   device-dependent colors, plain RGB values, no profile info 
available.
  - orange: colors from an absolute color space

Picture 1) was intended to show the situation before color management was
introduced: the RGB data gets exchanged between devices without any
conversion. The resulting colors are unknown as none of the devices
has been profiled or calibrated.


> All images in GIMP will have a color profile.  This will either be the 
> implicit sRGB profile, or some explicit profile.  Similarly, in the case 
> where the monitor has no explicit display profile, we send it RGB on the 
> assumption that it mostly conforms to sRGB.
> 
> More specifically, that means that everywhere we display an image will 
> be color-managed, even if that image isn't explicitly tagged with a 
> profile.  Color-related tools (the color picker comes to mind) should 
> always function relative to the color profile of the image, be it 
> explicit or implicit.  This may spell some interesting changes for 
> Curves and Levels down the line; I'm not sure.

oh, i meant to talk about the principal configurations / UX options.
I hope that there's no conflict with implementation issues by now.
I'm working on a set of use cases to use as a decision aid...


> I 
> also do not understand why 2a and 2b are separated.

the goal was to make explicit that importing unmanaged data
and creating unmanged data on export might be unrelated.

For example, 2b) might be a photographer that opens a ClayRGB file from
his archive and exports a JPG without any profile information, for web use.


regards,
yahvuu

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Re: [Gimp-developer] Color management dataflow [was: Color management (UI perspective for GIMP 2.8)]

2010-02-12 Thread Alexandre Prokoudine
On Fri, Feb 12, 2010 at 8:36 PM, Martin Nordholts wrote:

> People will want to create unmanaged images without a color profile for
> use on the web

That is, if people want to make everyone's lives more difficult, who
are we to stop them from doing so? :)

Just make web equal to sRGB as it already is.

Alexandre
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Re: [Gimp-developer] Color management dataflow [was: Color management (UI perspective for GIMP 2.8)]

2010-02-12 Thread Martin Nordholts
On 02/12/2010 06:27 PM, Omari Stephens wrote:
> On 02/12/2010 04:55 PM, yahvuu wrote:
>> Hi,
>>
>> here are some diagrams depicting selected configurations for colormanagement:
>> http://yahvuu.files.wordpress.com/2009/08/dataflow.png
>
> I believe number 1 is incorrect:
> All images in GIMP will have a color profile.

People will want to create unmanaged images without a color profile for 
use on the web for example, so we need to handle images with no color 
profile attached. I think introducing the conepts of "implicit profiles" 
adds unnecessary complexity.

  / Martin
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Re: [Gimp-developer] Color management dataflow [was: Color management (UI perspective for GIMP 2.8)]

2010-02-12 Thread Omari Stephens
On 02/12/2010 04:55 PM, yahvuu wrote:
> Hi,
>
> here are some diagrams depicting selected configurations for colormanagement:
> http://yahvuu.files.wordpress.com/2009/08/dataflow.png

I believe number 1 is incorrect:
All images in GIMP will have a color profile.  This will either be the 
implicit sRGB profile, or some explicit profile.  Similarly, in the case 
where the monitor has no explicit display profile, we send it RGB on the 
assumption that it mostly conforms to sRGB.

More specifically, that means that everywhere we display an image will 
be color-managed, even if that image isn't explicitly tagged with a 
profile.  Color-related tools (the color picker comes to mind) should 
always function relative to the color profile of the image, be it 
explicit or implicit.  This may spell some interesting changes for 
Curves and Levels down the line; I'm not sure.


For 2, an image that, when imported, does not have any explicit color 
profile information will be exported without saving any explicit color 
profile information (unless an explicit color profile was added).  I 
also do not understand why 2a and 2b are separated.

--xsdg
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