[Insight-users] GradientRecursiveGaussianImageFilter

[Luis Ibanez]

Hi Zein

1) Yes, the output of the GradientRecursiveGaussian filter
    is an image of vectors representing the gradient of the
    intensity values in the image. (covariant vectors to be
    precise).

http://www . itk . org/Insight/Doxygen/html/classitk_1_1GradientRecursiveGaussianImageFilter . html


2) Yes, this filter take the spacing into account. The gradient
    is reported as the variation of intensity per unit of spacing.
    e.g.   graylevel / millimeters.

   This means that if we have two images A and B with the same
   intensity pattern, and image A has double the spacing of
   image B, then the gradients computed from A will have half the
   value of the equivalent gradients computed from B.

   That's the reason why the gradient must be represented by
   itk::CovariantVectors instead of itk::Vectors.



Regards,



   Luis




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salah wrote:
> Hello all,
>  
> The output of the GradientRecursiveGaussianImageFilter is a vector
> image that represents the gradient of the input image. Is this true?
>  
> Does this filter take image spacings into account? In other words, are
> the gradient values measured in pixel units or real distance units?
>  
> Many thanks,
> Zein
>