Turn PDF into grayscale

[gabrielle harrison and Paul van den Bergen]

On Tue, 27 Jun 2006 09:08:00 +1000, Dariusz J. Garbowski  
<thuforuk at yahoo.co.uk> wrote:
> This is simple: gray colour is made of all three RGB channels having the  
> same value. Thus you have:
>
>    R   G   B  shade of gray
>    0   0   0  black
>    1   1   1  almost black
>    2   2   2  almost black
> ...
> 127 127 127  gray
> 128 128 128  a bit lighter gray
> ...
> 255 255 255  white
>
> what makes 256 colour space (or "gray space" ;-) This can only improve  
> if you have more bits-per-channel. Notice that 24 bit colour jpg is only  
> 8 bit per channel (3 channels * 8 bit = 24 bit).

So how is the gray scale value calculated?  is it just the average of the  
RGB values?

e.g. would

     R   G   B
     126 0   0
and
     R   G   B
     0   126 0
and
     R   G   B
     0   0   126

all convert to the same gray scale of

     R   G   B
     42  42  42

???





-- 
Dr Paul van den Bergen
Chance favours the prepared mind