Re: darkening colour

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From	Bartc <bc@freeuk.com>
Newsgroups	comp.programming
Subject	Re: darkening colour
Date	Mon, 06 Apr 2015 14:39:41 +0100
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On 06/04/2015 14:27, fir wrote:
> W dniu poniedziałek, 6 kwietnia 2015 15:17:32 UTC+2 użytkownik Bart napisał:
>> On 06/04/2015 12:38, fir wrote:

>>> ps for desaturation i use such code
>>>
>>>      float r = color.r;
>>>      float g = color.g;
>>>      float b = color.b;
>>>
>>> float p = sqrt( r*r*.299 + g*g*.587 + b*b*.114 ) ;
>>
>> Where is that formula from? Colour TV used to use:
>>
>>    Y = r*0.3 + g*0.6 +b*0.1
>>
>
> bnot sure uf you dont see that those two are the same (i found it as a random junk in google

If the two formulae do the same thing, then you're going a long way 
about it! Working out squares and square roots...

> http://alienryderflex.com/saturation.html

That doesn't explain it either. Why don't you just try the simpler 
formula and see it if makes a visible difference? If not, then you can 
try and see if a table lookup is quicker.

(I would say that most people wouldn't be able to tell if the colour 
balance is not quite right on a partly desaturated image. Such an image 
is unnatural anyway.)

-- 
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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