Re: Nullify blue

Greetings,

Not much of an expert in vision, but my two cents...

in RGB, it's quite impossible to determine what's "blue" and what's not,
since a certain combination of R, G & B might be low on the B but still
looks "blue" to the eye of the viewer. this is why its quite impossible to
determine "what is blue" (i.e. it is not only 0,0,255).

HSV mimic the human eye and gives blue a different representation namely,
from X to Y (no the Hue scale) it's all variant of blue (~195-295). the
level of S and V represent the how blue the color is (light, dark,
saturated, etc)

google for HSV color space to understand more, once you see the scheme you
will understnad it much better.

cheers,




On 1/30/06, Luiz Curado <lutitus@xxxxxxxxxxxx> wrote:
>
>  Please,
>
>   Can you explain to me why HSV space is better than RGB for this?
>
>   Regards,
>
>   Luiz Reginaldo
>
> Yoram Mizrachi <yorammizrachi@xxxxxxxxx> 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 "blues" 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 "blue" variant in a picture into black
> (RGB=000). I'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 "finger" numbers I can work with?
>
>   For example:
>   If (B > 200) && (R < 100) ?.
>
>   Thanks in advance,
>
>
>   Yoram Mizrachi
>
>
>
>
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--
Yoram Mizrachi
CTO, NexPerience


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