Image Processing Toolbox

imregionalmin

Find regional minima

Syntax

• BW = imregionalmin(I)
  BW = imregionalmin(I,CONN)
  

Description

BW = imregionalmin(I) computes the regional minima of I. The output binary image BW has value 1 corresponding to the pixels of I that belong to regional minima and 0 otherwise. BW is the same size as I.

Regional minima are connected components of pixels with the same intensity value, t, whose external boundary pixels all have a value greater than t.

By default, imregionalmin uses 8-connected neighborhoods for 2-D images and 26-connected neighborhoods for 3-D images. For higher dimensions, imregionalmin uses conndef(ndims(I),'maximal').

BW = imregionalmin(I,CONN) specifies the desired connectivity. CONN may have any of the following scalar values.

Value	Meaning
Two-dimensional connectivities
4	4-connected neighborhood
8	8-connected neighborhood
Three-dimensional connectivities
6	6-connected neighborhood
18	18-connected neighborhood
26	26-connected neighborhood

Connectivity may be defined in a more general way for any dimension by using for CONN a 3-by-3-by- ...-by-3 matrix of 0's and 1's. The 1-valued elements define neighborhood locations relative to the center element of CONN. Note that CONN must be symmetric about its center element.

Class Support

I can be any nonsparse, numeric class and any dimension. BW is logical.

Example

• A = 10*ones(10,10);
  A(2:4,2:4) = 3;  % minima 3 lower than surround
  A(6:8,6:8) = 8;  % minima 8 lower than surround
  A =
    10    10    10    10    10    10    10    10    10    10
    10     7     7     7    10    10    10    10    10    10
    10     7     7     7    10    10    10    10    10    10
    10     7     7     7    10    10    10    10    10    10
    10    10    10    10    10    10    10    10    10    10
    10    10    10    10    10     2     2     2    10    10
    10    10    10    10    10     2     2     2    10    10
    10    10    10    10    10     2     2     2    10    10
    10    10    10    10    10    10    10    10    10    10
    10    10    10    10    10    10    10    10    10    10
  
  B = imregionalmin(A)
  B = 
       0     0     0     0     0     0     0     0     0     0
       0     1     1     1     0     0     0     0     0     0
       0     1     1     1     0     0     0     0     0     0
       0     1     1     1     0     0     0     0     0     0
       0     0     0     0     0     0     0     0     0     0
       0     0     0     0     0     1     1     1     0     0
       0     0     0     0     0     1     1     1     0     0
       0     0     0     0     0     1     1     1     0     0
       0     0     0     0     0     0     0     0     0     0
       0     0     0     0     0     0     0     0     0     0
  

See Also

conndef, imreconstruct, imregionalmax

imregionalmax

imresize