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

[Jiang]

Hi Zach,
I figure the problem of using CannyEdgeDetection out. Since I render the
output of the CannyEdgeDetection directly. When I rescale the output to
[0,255], then the result is correct.
However there are a lot of noises in the output image. I consider it
because of=20
CannyFilter->SetVariance(1.0f);
CannyFilter->SetMaximumError(.01f);
How can I set an appropriate parameters for them?
Thanks a lot!


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