[vtkusers] Sobel Filter

[Jérôme]

Hi,
Sobel filter has several components in its output because it computes a
gradient
separately for x and y. You can use vtkImageMagnitude after your sobel to
get
only one component. This way, you can re-compute the sobel.

HTH
Jerome

2010/2/9 circass <circass at gmail.com>

>
> Hi David, thanx for your answer,
>
> Actually i m trying to make an edge detection operation and i want to make
> it repeatetly.
>
> I searched for it and find sobel Filter. is there any other filter you can
> advice me ?
>
> Thanx,
> Circass
>
>
> David Doria-2 wrote:
> >
> > 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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