AW: [SPAM:#] [Insight-users] Question about edge extraction

[Jiang]

Hi Zach,
thank you very much for your kind reply. I also tried Canny edge
detection provided by ITK as following:
	typedef itk::CannyEdgeDetectionImageFilter<InputImageType,
OutputImageType> CannyFilterType;
	CannyFilterType::Pointer CannyFilter =3D CannyFilterType::New();
	CannyFilter->SetInput(InputImage);
	CannyFilter->Update();
However, when I draw the output from CannyFilter on the screen, there is
nothing, only black.
And I tried to set the parameter as the example
\InsightToolkit-1.4.0\Testing\Code\BasicFilters\itkCannyEdgeDetectionIma
geFilterTest.cxx
	CannyFilter->SetVariance(1.0f);
    CannyFilter->SetMaximumError(.01f);
I get the same result.
I consider the canny edge detection should give good result for edge
extraction. How can I use it correctly?

Thank you again!

Best regards,

Chunyan Jiang

-----Urspr=FCngliche Nachricht-----
Von: Zachary Pincus [mailto:zpincus@stanford.edu]=20
Gesendet: Dienstag, 4. Mai 2004 09:44
An: Jiang
Cc: ITK
Betreff: Re: [SPAM:#] [Insight-users] Question about edge extraction

The Canny edge detection filter may prove useful here. (I suggest=20
looking over the myriad references about Canny edge detection on the=20
web, such as: http://homepages.inf.ed.ac.uk/rbf/HIPR2/canny.htm -- the=20
entire tutorial at this site is good.) A zero crossing filter may also=20
be good (tutorial also at the above site).

A canny filter (and to a lesser extent the zero crossing filter) is=20
nice because the edges are constrained to be one pixel wide, and can=20
extend through regions of low signal.

Zach


On May 4, 2004, at 12:22 AM, Jiang wrote:

> Dear ITK users,
>
> I want to extract the edge picture from one image. And I use
>
>  itk::GradientMagnitudeImageFilter
>
> It works fine. However the output is float type. I want to get binary=20
> output image. If I use
>
>  itk::BinaryThresholdImageFilter
>
> to filter the output to binary, and simply set=20
> SetUpperThreshold(),SetLowerThreshold() to some defined value, the=20
> binary edge is not good,
>
>  either with too much noise or the edge is not complete.
>
>  Could some one tell me how can I get good binary edge extraction=20
> result?
>
> =A0
>
> Thanks a lot!
>
> =A0
>
> =A0
>
> Chunyan Jiang