Groups | Search | Server Info | Keyboard shortcuts | Login | Register [http] [https] [nntp] [nntps]

Groups > comp.programming > #5384

Re: darkening colour

From Bartc <bc@freeuk.com>
Newsgroups comp.programming
Subject Re: darkening colour
Date 2015-04-06 14:17 +0100
Organization A noiseless patient Spider
Message-ID <mfu0vj$2cm$1@dont-email.me> (permalink)
References <7b8397af-4857-4de4-828f-a1ebe1b83ae1@googlegroups.com> <ti6kvne8w9v.11mahuf4ewkii$.dlg@40tude.net> <c4f6823f-25e4-4a41-b999-25015a70fa68@googlegroups.com>

Show all headers | View raw

On 06/04/2015 12:38, fir wrote:
> W dniu poniedziałek, 6 kwietnia 2015 10:53:03 UTC+2 użytkownik Dmitry A. Kazakov napisał:

>> P.S. Brightening is not always possible, because RGB color space does not
>> represent all visible colors. There are various techniques to approximate
>> lightening while keeping luminance, e.g. by compromising the color purity.
>>
>
> tnx for answer, is there maybe some simple c code recipe (procedure) for inc/dec of
> this more correct brightness?  this paper seems
> hard to read
>
> 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

to get luminance (those factors are approximate).

You can implement that using 3 256-byte lookup tables.

-- 
Bartc

Back to comp.programming | Previous | Next — Previous in thread | Next in thread | Find similar | Unroll thread

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

csiph-web