Re: median filter that preserves peaks

Posted by karo03 on Sep 07, 2013; 9:07am
URL: http://imagej.273.s1.nabble.com/median-filter-that-preserves-peaks-tp5004693p5004714.html

Ok, now I understand better.

What about applying top-hat filter with adequate size? Tophat means opening your image by a radius say 25 px and take the difference to the original. Threshold this difference and e.g. mask with it your original … This is a non-linear approach like median in comparison to the other recommendations!

Regards
Karsten

Am 06.09.2013 um 23:18 schrieb Neil Fazel <[hidden email]>:

> Thanks. I will look into that.
>
> I have attached a montage of 3 profile plots using 1) the original image, 2) image after applying median filter with radius 0.5, and 3) image after median filter with radius 1. You can see how the Y axis maximum of the plots goes from 3.28 to 3.15 to 3.13; the high frequency component has been reduced (good) at the same time that the peaks have been flattened (bad).
>
> I guess what I'm looking for is a filter that replaces local outliers (i.e. outliers in a neighborhood 2-3 pixels in each direction) with the median, but preserves them if they remain outliers in a larger neighborhood, which indicates that they are not noise but actual peak signal.
>
> Neil
>
>
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> ImageJ mailing list: http://imagej.nih.gov/ij/list.html
> <median filter flattens peaks somewhat.png>

Karsten
[hidden email]

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