imhmin (Image Processing Toolbox User's Guide)

Image Processing Toolbox User's Guide

H-minima transform

Syntax

```
I2 = imhmin(I,h)
I2 = imhmin(I,h,CONN)
```

Description

I2 = imhmin(I,h) suppresses all minima in the intensity image I whose depth is less than h, where h is a scalar.

Regional minima are connected components of pixels with a constant intensity value, and whose external boundary pixels all have a higher value.

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

I2 = imhmin(I,h,CONN) computes the H-minima transform, where CONN specifies the connectivity. CONN can 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

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 can 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 of any nonsparse numeric class and any dimension. I2 has the same size and class as I.

Example

Create a sample image with two regional minima.

a = 10*ones(10,10);
a(2:4,2:4) = 7;  
a(6:8,6:8) = 2  

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

Suppress all minima below a specified value. Note how the region with pixel valued 7 disappears in the transformed image.

b = imhmin(a,4)

b =

    10    10    10    10    10    10    10    10    10    10
    10    10    10    10    10    10    10    10    10    10
    10    10    10    10    10    10    10    10    10    10
    10    10    10    10    10    10    10    10    10    10
    10    10    10    10    10    10    10    10    10    10
    10    10    10    10    10     6     6     6    10    10
    10    10    10    10    10     6     6     6    10    10
    10    10    10    10    10     6     6     6    10    10
    10    10    10    10    10    10    10    10    10    10
    10    10    10    10    10    10    10    10    10    10

See Also

conndef, imhmax, imreconstruct

Reference

[1] Soille, P., Morphological Image Analysis: Principles and Applications, Springer-Verlag, 1999, pp. 170-171.

imhmax imimposemin