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imregionalmin

Regional minima

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Syntax

BW = imregionalmin(I)
BW = imregionalmin(I,conn)

Description

BW = imregionalmin(I) returns the binary image BW that identifies the regional minima in grayscale image I. Regional minima are connected components of pixels with a constant intensity value, surrounded by pixels with a higher value.

example

BW = imregionalmin(I,conn) specifies the desired connectivity, conn.

Examples

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Open Live Script

Create a simple sample array with several regional minima.

A = 10*ones(10,10);
A(2:4,2:4) = 3;       
A(6:8,6:8) = 8
A = 10×10

    10    10    10    10    10    10    10    10    10    10
    10     3     3     3    10    10    10    10    10    10
    10     3     3     3    10    10    10    10    10    10
    10     3     3     3    10    10    10    10    10    10
    10    10    10    10    10    10    10    10    10    10
    10    10    10    10    10     8     8     8    10    10
    10    10    10    10    10     8     8     8    10    10
    10    10    10    10    10     8     8     8    10    10
    10    10    10    10    10    10    10    10    10    10
    10    10    10    10    10    10    10    10    10    10

Calculate the regional minima. The function returns a binary image, the same size as the input image, in which pixels with the value 1 represent the regional minima. imregionalmin sets all other pixels in to 0.

regmin = imregionalmin(A)
regmin = 10x10 logical array

   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

Input Arguments

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Grayscale image, specified as a numeric array of any dimension.

Example: I = imread('cameraman.tif');

Data Types: single | double | int8 | int16 | int32 | int64 | uint8 | uint16 | uint32 | uint64 | logical

Pixel connectivity, specified as one of the values in this table. The default connectivity is 8 for 2-D images, and 26 for 3-D images.

Value

Meaning

Two-Dimensional Connectivities

4

Pixels are connected if their edges touch. The neighborhood of a pixel are the adjacent pixels in the horizontal or vertical direction.

3-by-3 pixel neighborhood with four pixels connected to the center pixel

Current pixel is shown in gray.

8

Pixels are connected if their edges or corners touch. The neighborhood of a pixel are the adjacent pixels in the horizontal, vertical, or diagonal direction.

3-by-3 pixel neighborhood with 8 pixels connected to the center pixel

Current pixel is shown in gray.

Three-Dimensional Connectivities

6

Pixels are connected if their faces touch. The neighborhood of a pixel are the adjacent pixels in:

  • One of these directions: in, out, left, right, up, and down

3-by-3-by-3 pixel neighborhood with 6 pixels connected to the faces of the center pixel

Current pixel is shown in gray.

18

Pixels are connected if their faces or edges touch. The neighborhood of a pixel are the adjacent pixels in:

  • One of these directions: in, out, left, right, up, and down

  • A combination of two directions, such as right-down or in-up

3-by-3-by-3 pixel neighborhood with 6 pixels connected to the faces and 12 pixels connected to the edges of the center pixel

Current pixel is center of cube.

26

Pixels are connected if their faces, edges, or corners touch. The neighborhood of a pixel are the adjacent pixels in:

  • One of these directions: in, out, left, right, up, and down

  • A combination of two directions, such as right-down or in-up

  • A combination of three directions, such as in-right-up or in-left-down

3-by-3-by-3 pixel neighborhood with 6 pixels connected to the faces, 12 pixels connected to the edges, and 8 pixels connected to the corners of the center pixel

Current pixel is center of cube.

For higher dimensions, imregionalmin uses the default value conndef(ndims(I),'maximal').

Connectivity can also be defined in a more general way for any dimension by specifying a 3-by-3-by- ... -by-3 matrix of 0s and 1s. The 1-valued elements define neighborhood locations relative to the center element of conn. Note that conn must be symmetric about its center element. See Specifying Custom Connectivities for more information.

Data Types: single | double | int8 | int16 | int32 | int64 | uint8 | uint16 | uint32 | uint64

Output Arguments

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Locations of regional minima, returned as a logical array of the same size as I. Pixels with the value 1 indicate regional maxima; all other pixels are set to 0.

Data Types: logical

Extended Capabilities

Version History

Introduced before R2006a

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See Also

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