Re: Nullify blue

RBG is probably the worst color space for color detection, because the 
color is expressed with the luminance of the scene added to all the 
three color components, if you use a different color space as for 
instance HSV, YUV, YCrCb, the luminance is expressed in only one of 
the channels and the other two represent the color, so it's easier to 
have color constancy troughout the image. There is another aproach to 
achieve color constancy in the RGB space wich is to normalize each of 
the components like this r=r/(r+g+b) b=b/(r+g+b) g=g/(r+g+b), this 
also produces some nice results in some cases.

Hope this helps

Best Regards

Zé Rui

--- In OpenCV@xxxxxxxxxxxxxxx, Luiz Curado <lutitus@xxxx> wrote:
>
> Please,
>    
>   Can you explain to me why HSV space is better than RGB for this?
>    
>   Regards, 
>    
>   Luiz Reginaldo
> 
> Yoram Mizrachi <yorammizrachi@xxxx> escreveu:
>         v\:* {behavior:url(#default#VML);}  o\:* {behavior:
url(#default#VML);}  w\:* {behavior:url(#default#VML);}  .shape 
{behavior:url(#default#VML);}        st1\:*{behavior:
url(#default#ieooui) }                Thanks Dave,
>    
>   Helped me a lot, indeed HSV is much better for &#8220;blues&#8221; 
identification 
>    
>   Cheers,
>   Yoram
>    
>    
>    
>       
> ---------------------------------
>   
>   From: OpenCV@xxxxxxxxxxxxxxx [mailto:OpenCV@xxxxxxxxxxxxxxx] On 
Behalf Of Dave Grossman
> Sent: Monday, January 23, 2006 9:42 PM
> To: OpenCV@xxxxxxxxxxxxxxx
> Subject: RE: [OpenCV] Nullify blue
> 
>    
>   You should be working in HSV space, not BGR space.
>    
>     
> ---------------------------------
>   
>   From: OpenCV@xxxxxxxxxxxxxxx [mailto:OpenCV@xxxxxxxxxxxxxxx] On 
Behalf Of Yoram Mizrachi
> Sent: Monday, January 23, 2006 7:24 AM
> To: OpenCV@xxxxxxxxxxxxxxx
> Subject: [OpenCV] Nullify blue
>   Greetings,
>    
>   I need to translate all &#8220;blue&#8221; variant in a picture into black 
(RGB=000). I&#8217;m working in BGR mode (the default) and was wondering 
what should be good values for each of the channels (R, G and B) to 
identify any variant of blue. 
>   Does anyone aware of a formula or &#8220;finger&#8221; numbers I can work 
with?
>    
>   For example:
>   If (B > 200) && (R < 100) &#8230;.
>    
>   Thanks in advance,
>    
>    
>   Yoram Mizrachi
>    
>   
> 
> 
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