Min/Max filter

Multidimensional non-linear min/max filtering

Description

The filter computes the minima and/or maxima of an array over sliding window with a given size.

Multidimensional array is fully supported: running filter in 1D, 2D filter for image processing applications (erosion/dilatation), 3D and more.

This package has been implemented with a special care on the running speed: the MEX engine uses an algorithms that requires no more than three (3) comparisons per element and per dimension in all configurations.

All numerical and logical class arrays are supported.

Contributor (beside author) is Vaclav Potesil

• Acknowledgements: This submission has inspired the following:; Free-knot spline approximation
• MATLAB release: MATLAB 7.8 (R2009a)
• Other requirements: MEX correctly setup NO image processing is required Download a tiff file for Lena's demo

[Tobias]

Nice Max-Filter. Works faster than implementation of Frederico D'Almeida and seems to be correct.

[Bruno Luong]

I copy the question from Michael Teo: Does it handle NaN data?

<QUOTE>
ePeriod = 3;
eData = [ 5;1;3;NaN;8;2;3;NaN;1;9 ];
minmaxfilt(eData, ePeriod, 'max', 'valid');

Actual output:
[5;3;3;NaN;8;3;3]

If we take NaN as a empty data, the expected output is:
[5;3;8;8;8;3;3]
</ENDQUOTE>

The answer is "no". The work around id to replace NaN by -Inf for running max and +Inf for running min.

 eData(isnan(eData))=-inf
 minmaxfilt(eData, ePeriod, 'max', 'valid')

[Michael Teo]

Thanks for sharing, its make sense and it solved my problem. :)

[shi]

 

[Qiao Liyong]