[Insight-developers] thresholding of gradient image

[Karthik Krishnan]

Leila baghdadi wrote:

>Hi everyone
>
>does anyone know what "hysteresis thresholding" is,
>  
>
 From what I remember at school, That works by specifying two 
thresholds, an upper and a lower. Gradient magnitudes greater than the 
upper threshold are classified as edges. Ones lower than the threshold 
are discarded. Ones in between are retained only if they are connected 
to a pixel classified as an edge.

If you resorted to simple thresholding, disjointed edges contours would 
result, since you would eliminate weak edges. With hysteresis you're 
connecting those weak ones to the strong ones, if there is a link.

Ref: Canny's paper.

>and if yes is there any filters in ITK that can apply it to a gradient
>  
>
Look at CannyEdgeDetectionImageFilter. You should be able to pull it out 
of there and package it into a separate filter (and put it back into ITK 
:) )

>image,
>
>
>Thanks
>
>
>Leila
>
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