Regional Maxima and Minima
- Regional Minima (Maxima) is a connected region such that every point in the neighbourhood of it has a strictly higher (lower) value.
- Real images usually have too many regional extrema (minima or maxima)
- Connected filtering can simplify these regional extrema
- The filtered regional extrema are usually very good markers for use in watershed segmentation
f=imread('ggray.tif');
fn=mmaddm(f,uint8(20*rand(size(f))));
mmsurfshow(fn);
rmax=mmregmax(fn);
mmshow(fn,rmax);
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f20=mmhdome(fn,20); mmsurfshow(f20); rmax20=mmregmax(f20); mmshow(fn,rmax20);
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- The regional maxima filtering can be used based on:
- Contrast: using h-dome
- Shape: using mmopen
- Area: using mmareaopen
More watershed demonstrations
Normally the markers are computed by filtering the extrema of the image.
- Normally a watershed segmentation requires internal and external markers. The external markers in many situations are computed using the watershed. See the demo: mmdcornea Segmentation of cornea cells