On 02/08/2010 01:39 AM, Graeme Gill wrote:
> Omari Stephens wrote:
>> Obviously, options for both of these things are "prompt the user."  It seems 
>> like there
>>   should be better alternatives, but I'm not sure what they might be.  
>> guiguru?  others?
> You're better having a set of defaults that the user can configure,
> so they aren't constantly hassled by prompts. The configuration can
> have options such as "prompt me" for certain combinations.

Yes.  By "prompt the user" I meant something similar to the current 
behavior when an image is tagged with a color profile other than the 
working space profile; the options are:
1) Do nothing
2) Convert to working space profile
3) Prompt the user

I was hoping someone would come up with a better convention, but since 
that doesn't seem to be happening, I will rev the spec and mention this 
UX paradigm explicitly, with the hope that it will be improved upon in a 
later revision.

>> Author:  Omari Stephens<x...@xsdg.org>  Version: 1 Date:    3 February 2010
>> 1) When an image is opened with no associated color profile, we assume that 
>> it is
>> encoded in sRGB space.
>> c) Convert the image from
>> the implicit profile to some explicit profile (AdobeRGB, ProPhotoRGB, sRGB, 
>> etc.)
> Not a good idea. There are losses in every color conversion. Ideally you want 
> to
> keep an image in its original format, unless the user explicitly decides to
> convert to another colorspace. Input is not the place to do this.
> So the application (GIMP) should have a transformation step available to:
>     1) Convert from one colorspace to another. If an image has no tag,
>        then both profiles would need to be specified.
>     2) Assign a profile to the image. This would set or override a tag.
> One idea to consider is the possibility of a "weak color tag". This
> is for a image that is to be considered un-tagged, but has a profile
> to specify the source colorspace for the purposes of display, and conversion.

Your "weak color tag" is exactly what I meant by an "implicit sRGB 
profile".  My judgment was that it wouldn't be useful to have a "weak" 
tag that wasn't sRGB — anything else should be explicit and embedded.

> There should be a "color tag" status somewhere for an image.
Because the only implicit color tag is sRGB, the absence of an 
icc-profile parasite (or an empty one) can be considered equivalent to 
the implicit sRGB tag.

>> 4) When an image with an explicit profile is exported
>> a) It will be tagged with that
>> profile in whatever way is appropriate for the file format.
>> b) If this is an sRGB PNG,
>> we need to decide between an sRGB chunk and sRGB profile.  See later 
>> discussion.
>> c) If the file format has no way to embed color profile information, (FIXME!)
> For c), have the option to covert to a particular colorspace (ie. sRGB).
Cool.  Any thoughts from other people?

> d) Have an option to write the file without an embedded profile. This is an 
> important
> option in regard to dealing with other applications, for instance sending 
> calibration
> or profiling files to a particular device.
I was thinking a tiny bit about this, but hadn't come up with anything 
conclusive.  I'll probably implement something trivial where you can 
select a menu item to dump the icc-profile.

>> 5) When an image with an implicit profile is exported a) The image is saved 
>> with no
>> color profile information.  For PNG, this means no sRGB chunk and also no 
>> iCCP chunk.
> You could really have the same options as 4, although you might default them
> differently.
Hmm; good point.  Will think about that.

> There are many possible ways of dealing with this issue. The important things 
> as
> I see them are 1) Allow defaulting to logical and useful workflows 2) Allow
> flexibility to accommodate particular needs.
Yup.  Thanks for thinking about this.

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