rgb to grayscale

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

Found some code:

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

--
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http://www.immersivelounge.com

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

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');
<snip>
> (.3*Red) + (.59*Green) + (.11*Blue)= Luminance/brightness
>
> I'm just wondering whether someone here has better ideas...

Although it might need some gamma correction, I would have thought that
the best starting point would be the size of the RGB vector - i.e.
grey = (255/442) * sqrt(red*red + green*green + blue*blue)

You tell us what looks better.

C.

C. wrote:

> Although it might need some gamma correction, I would have thought that
> the best starting point would be the size of the RGB vector - i.e.
> grey = (255/442) * sqrt(red*red + green*green + blue*blue)
>
> You tell us what looks better.
>

I think both formulas broduce similar results.
Anyway, judge by yourself (Be aware that you're going to open a ~1mb
htm file size, beacause I wanted to do some kind of css-art)

(I'll keep it online only a couple of days)
http://choringa.com.ar/test.htm

regards - julian