imhmax (Image Processing Toolbox User's Guide)

Image Processing Toolbox User's Guide

H-maxima transform

Syntax

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

Description

I2 = imhmax(I,h) suppresses all maxima in the intensity image I whose height is less than h, where h is a scalar.

Regional maxima are connected components of pixels with a constant intensity value, and whose external boundary pixels all have a lower value

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

I2 = imhmax(I,h,CONN) computes the H-maxima 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

a = zeros(10,10);
a(2:4,2:4) = 3;  % maxima 3 higher than surround
a(6:8,6:8) = 8;  % maxima 8 higher than surround
b = imhmax(a,4); % only the maxima higher than 4 survive.

See Also

conndef, imhmin, imreconstruct

Reference

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

imhist imhmin