Variance Filter question

[NatashaW]

Dear all,

Could someone tell me how does variance filter work and which article did they depend on in the implementation?
It's not the usual one and I want to know how it detects the edge?
I'm doing a summary about the functions that I'm using in my research ..

thank you so much for your help.

[Michael Schmid]

On 27 May 2010, at 17:56, NatashaW wrote:

> Dear all,
>
> Could someone tell me how does variance filter work and which  
> article did
> they depend on in the implementation?
> It's not the usual one and I want to know how it detects the edge?
> I'm doing a summary about the functions that I'm using in my  
> research ..
>
> thank you so much for your help.

Hi Natasha,

it simply calculates the variance,
   http://en.wikipedia.org/wiki/Variance
of the values inside a region. The size of the region is given by the  
radius; see Process>Filter>Show Circular Masks.

I don't see what should be unusual about it - maybe except that  
clipping of large values may occur if you don't use float (32-bit) data.

Michael

[NatashaW]

Got it .. Thank you Michael and Wayne