Wiener function : bug in the doc?

Wiener function : bug in the doc?


I was wondering whether there is a bug in the doc of the Wiener filter function:

THe doc says that the output is computed as:

Y = u + ( s^2 - n^2 )/ s^2 * ( x - u )


Y : filtered pixel output

u : average around that pixel

s^2 : stdDev around that pixel

n^2 : estimate of the noise stdDev

x : pixel value (src image)

What happens when s^2 < n^2 ? According to the equation, the output value would be inverted wrt to the input. Is there a sqr missing .. or am I completely lost ?



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Hello Gilbert,

I don't claim to understand the intricacies of the Wiener function, or its derivation. However; if you peruse the net you'll find this definition is consistent.


Hi Paul,

You are right, I also found the same definition on other sites. I still think that this is bad (possibility of signal inversion -- why would a filter do that?) but it has nothing with the IPP implementation. I probably need to improve my understanding on the basics of the Wiener filter.



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