ABX wrote:
> Would you like to give me values for 'correct/best' conversion from rgb to
> grey value without looking into POV sources ? I have found at least 3
> different versions of this conversion in POV sources and searching Internet I
> found even different. I have connected in PoPOV all occurences of such
> conversion into one define. Not convertable cases I have connected with unique
> constants. Now I'm not sure they use correct values...
> 
> ABX

There is no 'correct' conversion. But YIQ model, which is probably most 
used, uses values 0.299, 0.587, 0.114, which  are pretty close to 
GREY_SCALE macro. I think that best would be to go with these values. 
Strange value 0.229 in image.cpp is probably typo.
For definitive information check out colorspace faq:
http://www.faqs.org/faqs/graphics/colorspace-faq/

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