what RGB is blue?

[Bob Sneidar]

Well remember that we perceive color in reference to the colors around it. What he might pick on a color wheel might not seem all that blue when it is by itself or nearby other colors. 

Bob


On Jul 1, 2011, at 2:55 AM, Keith Clarke wrote:

> Hi Tiemo,
> Not a colour expert but it's an interesting problem - especially as 'blueness' may be subjective.
> 
> I visualise RGB values correlating with x, y, and z axis values of a colour 'sphere' where the origin is black and the surface, at cube-root(r-cubed + g-cubed + b-cubed) where r, g and b all = 255, is white.
> 
> Maybe you can define a section of that sphere's volume which is consistently blue in nature, given your target hues? Maybe the surface area of this section volume is defined by a slice (what is a 3D 'chord'?) by specific colours on the blue-red, blue-green spectra?
> 
> That's probably all rubbish but you never know? :-) 
> Best,
> Keith..
> 
> On 1 Jul 2011, at 10:39, Tiemo Hollmann TB wrote:
> 
>> Hello,
>> 
>> I am taking the mousecolor at different points from an image by script (not
>> by clicking). I would like to analyse if the color I've taken is a "kind of
>> blue", or another color. I want to change the backgroundcolor of an image.
>> The background is always blue, but different blues and changing over the
>> background. So what I want to do is to verify, what is background and what
>> is foreground of my image.
>> 
>> 100% pure blue would be 0,0,255. But for a human being 25,75,130 (greyblue)
>> is also still blue, but 240,20,180 is pink, though the third RGB value is
>> higher as in my greyblue.
>> 
>> So I can't just check only the third RGB value, neither the sum or cross
>> total. Has anybody ever heard, if you can define at all by math "what is
>> blue"?
>> 
>> Any color specialist around here?
>> 
>> Tiemo
> 
> 
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