[Vv] How is the value of pixel of vector image calculated?

[Rômulo Pinho]

Hello, Chester,

If you open the vector field (VF) as a regular image, the value 
displayed is meaningless in practice, yet cool to look at... ;-) We 
don't even know what it is, to be honest, but it seems to be related to 
how the image conversion between ITK and VTK is done. However, if you 
open the VF in overlay mode (menu "Overlay"/"Add deformation field to 
current image" or click with the right mouse button on the image file) 
what is shown in the overlay tab is the magnitude of the vector at the 
pixel location and you will also see the arrows corresponding to vectors 
on the image. Actually, it is better (and much cooler!) to always use 
the overlay mode for VF visualization.

Hope it helps.
Kind regards,

Rômulo

-- 
Rômulo PINHO
Post-doc Research Engineer
Centre Léon Bérard
28, rue Laennec 69373
Lyon, France
+33 (0)4 78 78 51 50
romulo.pinho at lyon.unicancer.fr
http://www.creatis.insa-lyon.fr/rio/RomuloPinho



On 05/11/2012 07:04 AM, 黄成 wrote:
> Hi all,
>
>        I notice that if I load a vector image using "vv", this 
> application will assign a double value for every pixel. How is this 
> value calculated? Is this value equal to the pixel vector point 
> multiply its gradient vector? If that, how is the gradient vector 
> calculated?
>
> -- 
> Chester Huang
>
> Shenzhen Institutes of Advanced Technology,Chinese Academy of Sciences
>
> Address:Human-Computer Interaction Center ,No.1068,Xueyuan Road,Xili 
> University Town,Nanshan District,Shenzhen City，518055
>
>
> _______________________________________________
> vv mailing list
> vv at creatis.insa-lyon.fr
> http://www.creatis.insa-lyon.fr/mailman/listinfo/vv
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