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mmcwatershed
Detection of watershed from markers.

Synopsis

function Y = mmcwatershed ( f , g , Bc , LINEREG )

Input

f Image Gray-scale (uint8 or uint16) image
g Image Gray-scale (uint8 or uint16) or binary image

marker image: binary or labeled.
Bc Structuring Element

Default: 3x3 elementary cross

(watershed connectivity)
LINEREG String

Default: 'LINES'

Output image: 'LINES' or 'REGIONS'.

Output

Y Image Gray-scale (uint8 or uint16) or binary image

Description

mmcwatershed creates the image y by detecting the domain of the catchment basins of f indicated by the marker image g, according to the connectivity defined by Bc. According to the flag LINEREG y will be a labeled image of the catchment basins domain or just a binary image that presents the watershed lines. To know more about watershed and watershed from markers, see [BM93]. The implementation of this function is based on [LF00].

WARNING: There is a common mistake related to the marker image g. If this image contains only zeros and ones, but it is not a binary image, the result will be an image with all ones. If the marker image is binary, you have to set this explicitly using the logical function.

Examples

a = uint8([...

    10   10   10   10   10   10   10;...

    10    9    6   18    6    5   10;...

    10    9    6   18    6    8   10;...

    10    9    9   15    9    9   10;...

    10    9    9   15   12   10   10;...

    10   10   10   10   10   10   10]);

b = mmcmp(a,'==',uint8(6))

b =
     0     0     0     0     0     0     0
     0     0     1     0     1     0     0
     0     0     1     0     1     0     0
     0     0     0     0     0     0     0
     0     0     0     0     0     0     0
     0     0     0     0     0     0     0

mmcwatershed(a,b)

ans =
     0     0     0     1     0     0     0
     0     0     0     1     0     0     0
     0     0     0     1     0     0     0
     0     0     0     1     0     0     0
     0     0     0     1     0     0     0
     0     0     0     0     1     0     0

mmcwatershed(a,b,mmsecross,'REGIONS')

ans =
      1      1      1      1      2      2      2
      1      1      1      1      2      2      2
      1      1      1      1      2      2      2
      1      1      1      1      2      2      2
      1      1      1      1      2      2      2
      1      1      1      1      2      2      2

f=mmreadgray('astablet.tif');

grad=mmgradm(f);

mark=mmregmin(mmhmin(grad,17));

w=mmcwatershed(grad,mark);

mmshow(grad);

mmshow(mark);

mmshow(w);
grad mark
w

Equation

Equation (watershed regions):
Minimum length of a point to a set:
Length of a point to a set:
Where:
is the path between the point x and subset X under connectivity Bc

See also

mmfreedom Control automatic data type conversion.
mmwatershed Watershed detection.
mmsebox Create a box structuring element.
mmsecross Diamond structuring element and elementary 3x3 cross.
mmswatershed Detection of similarity-based watershed from markers.
mmdcalc Extract the keys of a calculator.
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