Hi, Michael. Thank you very much for the answer.
I have developed nonlinear filtering algorithms and implemented them as plugins, taking one of the freely available plugins described in the package ImageJ as a prototype. I want to compare the filter de-noising efficiency for some of the test 2D gray-scale images. But I can only calculate the difference between the test and filtered images using Image Calculator, and to obtain the total mean value (Analyze - Measure). Is it possible to obtain the filter efficiency estimation, for example, by means of “Peak Signal-to-Noise Ratio”, using ImageJ program? Yours sincerely, Nataliya вт, 25 бер. 2025 р. о 13:30 Michael Schmid <[email protected]> пише: > Hi Nataliya, > > both, Median and Median 3D use a circular support (circular Kernel). > I noticed that Median 3D (and the other 3D filters) use a slightly > different definition of the radius. > For the 3D filters, sometimes one needs to add a small number like 0.5 > to the radius of the 2D filters. > For a 2D image (no stack), Median 3D with radius=2.5 in x&y and the > "usual" (2D) Median with radius=2 do exactly the same (except near the > edges, see below). > At some radius values. the behavior is the same for the 2D and 3D > filters (e.g. radius=10.5 and 14.5), so there is no simple rule. > I think that eventually the 3D filters should be modified to use the > same definition of the radius as the 2D filters, the one also used for > Process>Filters>Show circular masks. > > The remaining difference is the handling of the edge pixels. > The 3D filters consider the out-of image pixels as nonexistent. Thus, > when calculating the median near the edge, the 3D median uses fewer > pixels. The 2D filters (the "usual" Median, Mean, etc.) assume that the > out-of-image pixels are the same as the nearest edge pixel, and the > mean, median, etc. is always calculated over the same number of pixels > (except for float images with NaN = Not a Number). > The latter convention (assuming repeated edge pixels) is the usual > convention in ImageJ, also for Gaussian Blur, and the Process>Binary > functions. > > Hope this helps, > > Michael > ________________________________________________________________ > > > On 22.03.25 12:32, Наталія Тулякова wrote: > > Dear colleagues. > > I am interested in filtering 2D images. The ImageJ program has two median > > filters in the "Process-Filters" menu item. I have not found any > > documentation explaining how "Median 3D" works. Median 3D provides better > > results than Median. What is the difference between them for 2D image > > processing? Does "Median 3D" use a square window while "Median" uses a > > circular window? > > > > With best regards, Nataliya > > > > -- > > ImageJ mailing list: http://imagej.nih.gov/ij/list.html > > -- > ImageJ mailing list: http://imagej.nih.gov/ij/list.html > -- ImageJ mailing list: http://imagej.nih.gov/ij/list.html
