[Insight-users] Sobel operator gives fat edges

[Sergio Vera]

Have you tried CannyEdge Detection Filter? Canny always returns the
thinnest edges.

Hope to help Regards

On Wed, Mar 14, 2012 at 2:59 AM, Emma Ryan <eryanvtk at yahoo.com> wrote:

>
> Hi ,
>
>    I am using the sobelOperator provided in itk.  The following is my code
> snippet. I would like to understand
>
> 1.  the default setting of the sobel and
> 2. how I can tune it. There dont seem to be too many member functions to
> manipulate the sobel.
> 3. If I need to use Erosion filter to thin the edges, how do I design a
> 'line' structuring element. My code ( also added below) does not seem to
> allow line (which I am guessing derives from Box, line = 1-D Box)
>
> Any help/suggestions is truly appreciated.
>
> Thank you,
> Emma
>
>
> typedef itk::ConstNeighborhoodIterator<ImageType> NeighborhoodIteratorType;
>     typedef itk::ImageRegionIterator< ImageType>        IteratorType;
>
>     itk::SobelOperator<PixelType, 2> sobel;
>     sobel.SetDirection(1);
>     itk::Size<2> radius_s;
>     radius_s.Fill(1);
>     sobel.CreateToRadius(radius_s);
>
>
>     NeighborhoodIteratorType::RadiusType radius = sobel.GetRadius();
>     NeighborhoodIteratorType it( radius, my_image,
> my_image->GetRequestedRegion() );
>     itk::NeighborhoodInnerProduct<ImageType> inner_product;
>
>     ImageType::Pointer output = ImageType::New();
>     output->SetRegions(my_image->GetRequestedRegion());
>     output->Allocate();
>
>     IteratorType out(output, my_image->GetRequestedRegion());
>
>     for (it.GoToBegin(), out.GoToBegin(); !it.IsAtEnd(); ++it, ++out)
>     {
>      out.Set( inner_product( it, sobel ) );
>     }
>
>     output->Update();
>
>
> //Erosion Structuring Element: The following fails to compile if I use '1'
> instead of '2'
> typedef itk::FlatStructuringElement<2> StructuringElementType;
>     StructuringElementType::RadiusType element_radius;
>     element_radius.Fill(5);
>
>     StructuringElementType strel =
> StructuringElementType::Box(element_radius);
>
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-- 
Sergio Vera

 Alma IT Systems
 C/ Vilana, 4B, 4º 1ª
 08022 Barcelona
 T. (+34) 932 380 592
 www.alma3d.com
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