[vtkusers] Sobel Filter

[David Doria]

On Tue, Feb 9, 2010 at 8:53 AM, circass <circass at gmail.com> wrote:

>
> Hi my friends,
> i m trying to use sobel filter, it works at the first time but when i try
> to
> make a second filtering on filtered image it gives me an error about scalar
> component number. it says it can work with only one scalar component.
>
> Thanx, Circass.
>
>
The problem is that vtkImageSobel2D produces a vector image:

vtkImageSobel2D <classvtkImageSobel2D.html> computes a vector field from a
scalar field by using Sobel functions. The number of vector components is 2
because the input is an image. Output is always doubles.

This "image" has a vector (more than one component) at each "pixel". This is
why you can't filter it again. I actually don't understand though, I thought
the Sobel filter just multiplied a mask such as

1 0 1
2 0 2
1 0 1

at each pixel to come up with a scalar at each pixel?

Thanks,

David
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