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Laplacian Filter

Posted: Thu Oct 28, 2021 6:48 pm
by Scottk
In the layers module, how about adding a Laplacian filter? I knw the Sobel filter is there but adding a second order filter could provide more possibilities.

Re: Laplacian Filter

Posted: Sun Oct 31, 2021 12:00 am
by admin
Is this for edge detection/enhancement purposes? If so, would you find a Laplacian over Gaussian more useful?

Re: Laplacian Filter

Posted: Mon Nov 01, 2021 1:22 pm
by Scottk
Ivo,

Yes I am thinking about edge detection and enhancement. Please elaborate on how the Gaussian could be used. I would think that this would have the opposite effect.

Thanks.

Re: Laplacian Filter

Posted: Tue Nov 02, 2021 11:24 pm
by admin
Scottk wrote: Mon Nov 01, 2021 1:22 pm Ivo,

Yes I am thinking about edge detection and enhancement. Please elaborate on how the Gaussian could be used. I would think that this would have the opposite effect.

Thanks.
The problem with using a Laplacian filter alone is that the output is quite noisy and doesn't yield good/smooth edges. It is often combined with a Gaussian Filter.

I will implement this for the next beta.

In the meantime, also have a look at the Fractional Differentiation filter (paper here) in the Layer module, which is much more useful for astronomical purposes (e.g. it is very adept at visualising structures that are otherwise very difficult to see).

Re: Laplacian Filter

Posted: Fri Nov 12, 2021 3:41 am
by admin
A Laplacian over Gaussian filter is now available in the Layer module in 1.8.519 beta. Any trouble, do let me know.