Re: Does colour manager automatically modify the display

[Richard Hughes <hughsient gmail com>]

On 25 September 2010 14:15, Aravindh M <aravindh 2138 gmail com> wrote:
> This is my first post to a linux/gnome related mailing list.

Welcome!

> I am new to the concept of colour management and colour models and still do
> not understand it. I tried reading about CIE1931 and tongue diagram but
> could not understand most of the wiki page. I am a computer science student
> and this is my first encounter with colour management.

Right, it's a pretty daunting subject for something as simple as "color" :-)

> I have written openGL code (using freeglut library) to display coloured
> squares with RGB values (159, 0, 0), (147, 147, 0), (0, 0, 255), (0, 129,
> 129)  {Using glColor function}. I have set colour manager to default
> settings.

Right. It really depends on lots of things what "color" you see:

* If the display is color managed and "corrected"
* If the display is old, and the backlight is yellowing and dimmer
* The ambient light in the room
* The operating system and the drivers you are using
* If the application is "color managed"

> Does this make the actual displayed colour independent of the monitor? Is
> the gnome colour manager influencing the actual displayed colour? If yes,
> what transformation does it do in default settings.

By default, gnome-color-manager does nothing. If you assign it a
profile, it loads some data into X to change the 2D tables of color
mapping (so called "gamma tables") -- this makes your display look
'different'.

If you assign a profile, GCM sets some settings that make color
managed applications take notice of the new profile, and the colors
that are sent to the monitor are changed accordingly.

> I do not plan to print or do anything else with the colours. I just want to
> render them.

What do you want to achieve? Perfect rendition of a specific color, or
just knowing what's going to affect the colors in use on random
computers? We're a pretty friendly group of people, so don't be afraid
to ask.

Richard.