Posted by lorento on 07/04/06 11:18

Found some code:

$grey= 0.2125*$rgb['red']+ 0.7154*$rgb['green']+ 0.0721*$rgb['blue'];

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julian_m wrote:
> Do anyone know an algorithm which retieves a grey value given certain
> rgb value?
>
> I'm needing this kind of function:
>
> $grey = RGBtoGrey('#ffffff');
>
> where $grey (function's return value) should be a real number in [0;1]
> range
>
> Googling a little bit, I found an equation which seems to be aplied by
> many photo-editor software
>
> (.3*Red) + (.59*Green) + (.11*Blue)= Luminance/brightness
>
> I'm just wondering whether someone here has better ideas...
>
> regards - julian

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