bwulterode (Image Processing Toolbox User's Guide)

Image Processing Toolbox User's Guide

Ultimate erosion

Syntax

BW2 = bwulterode(BW)
BW2 = bwulterode(BW,METHOD,CONN)

Description

BW2 = bwulterode(BW) computes the ultimate erosion of the binary image BW. The ultimate erosion of BW consists of the regional maxima of the Euclidean distance transform of the complement of BW. The default connectivity for computing the regional maxima is 8 for two dimensions, 26 for three dimensions, and conndef(ndims(BW), 'maximal') for higher dimensions.

BW2 = bwulterode(BW,METHOD,CONN) specifies the distance transform method and the regional maxima connectivity. METHOD can be one of the strings 'euclidean', 'cityblock', 'chessboard', and 'quasi-euclidean'.

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

BW can be numeric or logical and it must be nonsparse. It can have any dimension. The return value BW2 is always a logical array.

Example

originalBW = imread('circles.png');
imshow(originalBW)
ultimateErosion = bwulterode(originalBW);
figure, imshow(ultimateErosion)

See Also

bwdist, conndef, imregionalmax

bwtraceboundary bwunpack