Posted by
Michael Schmid on
May 09, 2014; 9:01am
URL: http://imagej.273.s1.nabble.com/Algorithm-Difference-between-Median-Filter-And-Median-Inside-Rank-Filter-tp5005217p5007655.html
Hi,
when referring to 'RankFilters', this usually means the built-in filters of ImageJ, such as mean, median, minimum, maximum in Process>Filters. Many built-in filters are actually plugins.
Fast Filters (external plugin): In contrast to the built-in RankFilters, it does not take a (roughly) circular area where the pixels are read from ('support' or 'kernel' area) but a square area. For the median, it actually does not calculate the median inside this square area, but it first calculates the median for the lines, then for the columns of the median-filtered lines. This is a bit faster than the median over the square area would be, but it does not always give the same result. Nevertheless, it is almost as good as a 'true' median.
The built-in Process>Filters>Median (RankFilters) and the Fast Filters internally use 32-bit float data. Other image types are converted to 32 bits.
Some other external filters cannot handle float data, e.g. the fast median
http://ij-plugins.sourceforge.net/plugins/filters/ works only on 8-bit and 16-bit data (but it is faster than the built-in version).
I don't know which external Median_filter plugin is the one you are interested in? In any case, you can simply try whether it works for your data.
Michael
________________________________________________________________
On May 8, 2014, at 23:55, m_azodi wrote:
> Hi Michael,
>
> If I am right, we do have three different Median Filters here:
> 1) RankFilters plugin
> 2) FastFilters plugin (less accuracy but fastest one)
> 3) Median_filter plugin
> I am wondering if all of the mentioned plugins could perform median filter
> on 24 or 32-bit images?
> Apart from them, do you suggest any other median filter algorithm (outside
> of the concept of imageJ framework) which would perform fast on processing
> 24 or 32-bit images? If yes, then please leave me the implementation link.
>
> Thanks in advance.
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