Re: darkening colour

From	Bartc <bc@freeuk.com>
Newsgroups	comp.programming
Subject	Re: darkening colour
Date	2015-04-06 12:54 +0100
Organization	A noiseless patient Spider
Message-ID	<mfts3k$h0u$1@dont-email.me> (permalink)
References	<7b8397af-4857-4de4-828f-a1ebe1b83ae1@googlegroups.com> <ti6kvne8w9v.11mahuf4ewkii$.dlg@40tude.net> <mftmmf$v1m$1@dont-email.me> <yqq9p8b8i35g.17lvryrg42xrh.dlg@40tude.net>

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On 06/04/2015 11:44, Dmitry A. Kazakov wrote:
> On Mon, 06 Apr 2015 11:21:57 +0100, Bartc wrote:
>
>> On 06/04/2015 09:52, Dmitry A. Kazakov wrote:
>>> On Mon, 6 Apr 2015 01:12:42 -0700 (PDT), fir wrote:

>>>> r*=f;
>>>> g*=f;
>>>> b*=f;

>>>> or there is something better maybe?
>>>
>>> Convert RGB to the L*a*b color space change luminance, convert back.
>>> A less computation intensive model...
>>
>> Is that what happens when I adjust the brightness control on my HD TV? I
>> wonder they use to do these computations at 50M pixels per second.
>
> No idea. Is it digital all the way?

Digital until it gets to the ADC I expect (unless the LCD elements are 
digitally modulated). I don't think the brightness is adjusted by 
varying the back-lighting.

My point is that it might not be feasible to perform expensive per-pixel 
computations in the way you suggest (although it would likely work in 
YUV not RGB, which might be a little easier.).

Maybe there is a easier way even if the colour is not exact - the OP is 
creating some sort of video game not trying to get a perfect colour 
rendition of an Old Master.

For example, if I look at a (halftone) printed colour image under a lamp 
(I won't go into the colour cast that that will give), then change the 
40W bulb for a 60W one, the picture will look brighter. But surely all 
I'm looking at is the 50% (or whatever) brighter reflection from C,M,K 
dot? Each dot will reflect light independently of its neighbours. That 
sounds like what the OP is proposing.

-- 
Bartc

Thread

darkening colour fir <profesor.fir@gmail.com> - 2015-04-06 01:12 -0700
  Re: darkening colour "Dmitry A. Kazakov" <mailbox@dmitry-kazakov.de> - 2015-04-06 10:52 +0200
    Re: darkening colour Bartc <bc@freeuk.com> - 2015-04-06 11:21 +0100
      Re: darkening colour "Dmitry A. Kazakov" <mailbox@dmitry-kazakov.de> - 2015-04-06 12:44 +0200
        Re: darkening colour Bartc <bc@freeuk.com> - 2015-04-06 12:54 +0100
          Re: darkening colour "Dmitry A. Kazakov" <mailbox@dmitry-kazakov.de> - 2015-04-06 14:27 +0200
          Re: darkening colour fir <profesor.fir@gmail.com> - 2015-04-06 05:51 -0700
    Re: darkening colour fir <profesor.fir@gmail.com> - 2015-04-06 04:38 -0700
      Re: darkening colour "Dmitry A. Kazakov" <mailbox@dmitry-kazakov.de> - 2015-04-06 14:52 +0200
        Re: darkening colour fir <profesor.fir@gmail.com> - 2015-04-06 06:25 -0700
          Re: darkening colour "Dmitry A. Kazakov" <mailbox@dmitry-kazakov.de> - 2015-04-06 17:02 +0200
            Re: darkening colour fir <profesor.fir@gmail.com> - 2015-04-06 09:36 -0700
              Re: darkening colour "Dmitry A. Kazakov" <mailbox@dmitry-kazakov.de> - 2015-04-07 10:52 +0200
                Re: darkening colour fir <profesor.fir@gmail.com> - 2015-04-07 02:10 -0700
                Re: darkening colour "Dmitry A. Kazakov" <mailbox@dmitry-kazakov.de> - 2015-04-07 11:30 +0200
                Re: darkening colour fir <profesor.fir@gmail.com> - 2015-04-07 03:24 -0700
                Re: darkening colour "Dmitry A. Kazakov" <mailbox@dmitry-kazakov.de> - 2015-04-07 13:00 +0200
      Re: darkening colour Bartc <bc@freeuk.com> - 2015-04-06 14:17 +0100
        Re: darkening colour fir <profesor.fir@gmail.com> - 2015-04-06 06:27 -0700
          Re: darkening colour Bartc <bc@freeuk.com> - 2015-04-06 14:39 +0100
            Re: darkening colour fir <profesor.fir@gmail.com> - 2015-04-06 06:48 -0700
              Re: darkening colour Bartc <bc@freeuk.com> - 2015-04-06 16:02 +0100
                Re: darkening colour fir <profesor.fir@gmail.com> - 2015-04-06 09:44 -0700
                Re: darkening colour Bartc <bc@freeuk.com> - 2015-04-06 21:05 +0100
                Re: darkening colour fir <profesor.fir@gmail.com> - 2015-04-07 00:51 -0700
                Re: darkening colour fir <profesor.fir@gmail.com> - 2015-04-07 01:12 -0700

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