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Re: Default colors vs. gamma


From: Fred Kiefer
Subject: Re: Default colors vs. gamma
Date: Mon, 01 Nov 2004 12:03:50 +0100
User-agent: Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.6) Gecko/20040114

Quentin Mathé wrote:
Le 31 oct. 04, à 21:56, Fred Kiefer a écrit :

Quentin Mathé wrote:

The topic as far as I remember was not, if GNUstep will need Gamma correction in some way (which I strongly agree to, but rather as part of full colour management), what was actually discussed was a specific proposal to gamma correct the system colours when creating them from values and this is what I opposed. As Alexander already explained we will be losing the benefit of linearity in colour values, if we apply gamma correction in the GUI. Also correctiong only some of the values may result in a worse effect than correcting none.

To restate this even clearer: I am "For" gamma correction, but against the proposed patch and anything similar to it.

But in the GNOME or KDE cases, is their default gamma support based on a CMS, or is their default gamma just a hack which breaks linearity. … Last point, long time before ColorSync (the Mac OS CMS) exists, Mac OS was using a 1.8 gamma, do you think at this time the linearity was broken also because of the non existent CMS ?


Looks like my mail was still unclear in what I propose. Sorry for that. I suggest that we don't implement the gamma correction when defining the system colours (I hope this part was clear), but instead implement it as a conversion between calibrate colour spaces and device colour spaces. you see, whenever we want to set a calibrated colour in a device it should be converted to the device colour space. I hope I did put in a comment on this, when I rewrote the colour classes. I think it would be best to have a full CMS impelemented here for the conversions. If you think this is hard remember that the original cairo backend had colour management implemented and that one of the drawing applications, I think it was Cenon, comes with colour management build in. Even if we don't use a CMS library here this conversion is the place where gamma correction should be put. Of course this will require a few more extensions, devices should know about their colour space and that information should be used here and so one, but by using this we would imporve display on the monitor, while not losing (perhaps even gaining) in PS and printer output.

If this mail is still unclear, I'll give up and start to code it. Words are so complicated, Objective-C is so easy...

Fred




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