[Development] Color Management support in Qt 5?

[Kai-Uwe Behrmann]

Am 08.11.2013 14:17, schrieb Sorvig Morten:
> 
> On 07 Nov 2013, at 12:48, Kai-Uwe Behrmann <ku.b at gmx.de> wrote:
> 
>> Detecting a colour space and converting to device colour spaces is around the same amount of developer time as for special casing sRGB. Detecting sRGB among hundrets of ICC profiles is not trivial or fast, while such a detection does not matter in a generic colour managed environment.
>>
>> EXT_texture_sRGB provides only sRGB gamma to linear gamma conversions. That is a thiny bit of grafic processing, which is needed for handling colour space conversions. 
>> The spec is clear to not doing anything about dislpaying sRGB images on a monitor. So this OpenGL extension does not help much with colour management.
>>
>> Short term support for sRGB only would make Qt a pretty limiting choice for many colour managed applications.
>>
>> IMHO, limiting support to RGB in a first development stage is a more sound target.
> 
> 
> Hello! 
> 
> You did not give me much wiggle room with this reply - did you simply want to end the discussion?

Oh, I joined the discussion to keep it alive. Sorry, if my reply was
perceived in a different mode.

> For example, the existance of EXT_framebuffer_sRGB supports my argument that limiting support to sRGB will be simpler, but you don’t mention it at all.

As I mentioned, the GL extension does no complete colour space
conversion as it handles only gamma and not colour primaries. It is
intented for memory storage savings, which are unrelated to any colour
management concerns. In fact a small shader can do a similar gamma
correction. On the other hand a different shader could do as well a full
colour space conversion. sRGB is other than for storage not of much value.

Nonetheless sRGB is traditionally used as factual blending space. But
e.g. wayland devs think seriously around linear gamma blending spaces,
which give lesser artefacts.

If one plans for mobile only, then a single blending colour space with
low bit depth storage might be an option. But I wanted to point out,
that this appears to me like a serious regression on desktop. The
implications are certainly up to decide by the Qt community.

kind regards
Kai-Uwe Behrmann