bwborder

Border detection for binary images

Calling Sequence

B = bwborder(Img)

B = bwborder(Img, 4)

B = bwborder(Img, 8)

Parameters

Img: binary array, 1 for object and 0 for background (double precision)
B: binary(0-1) array (double), same size as Img

Description

Extracts contours from binary images, by detecting which pixel valued 1 has at least one neighbor valued 0. The second argument is 4 or 8 depending if the detection is to be made in 4- or 8-neighborhood. The final border will be 8-connected if 4-neighbors are used, and 4-connected if 8-neighbors are used.

bwborder(Img): equals bwborder(Img, 8).

Examples

initial_dir = PWD;
chdir (SIPDIR + 'images');

Img = imread('star.bmp')
clf
imshow(Img,2);

B = bwborder(Img)
imshow(B,2);

// exercise: define a small matrix of 0's and 1's, 
// with the 1's forming a distinct object (like a square),
// then run bwborder to see what it does to the matrix.

chdir(initial_dir);

Authors

Ricardo Fabbri <ricardofabbri[at]users.sf.net>

Availability

The latest version of SIP can be found at

http://siptoolbox.sf.net