Image Processing Toolbox

bwulterode

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', or 'quasi-euclidean'.

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

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

• bw = imread('circles.tif');
  imshow(bw), title('Original')
  bw2 = bwulterode(bw);
  figure, imshow(bw2), title('Ultimate erosion')
  

See Also

bwdist, conndef, imregionalmax

bwselect

bwunpack