follow

Parameters

Img: binary 2D array, 1 for object and 0 for background (class double)
x y: vectors, storing the parametrized contour.

Description

Function follow extracts parametric contours of binary objects. This is useful for further extracting object features such as curvature and bending energy.

It is assumed that Img has only one object

x and y both store the parametrized contour. In other words, (x(i), y(i)) is a point of the contour, where the coordinate system is assumed as starting from bottom-left corner (0,0) to uper-right corner of the image. To get the (row,col) matrix coordinates, use the transformation below:

row = size(Img,'r') - y
col = x+1

The second argument is an optional parameter, being 4 or 8 depending if the border following is to be made in 4- or 8-neighborhood sequence, yielding a 4- or 8-connected contour.

follow(Img) equals follow(Img, 8).

Examples

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

Img = imread('star.bmp');
xset('window',0)
clf
imshow(Img,2);
[x,y] = follow(Img);
xset('window',1)
clf
plot2d(1:size(x,'*'),x,2);
plot2d(1:size(y,'*'),y,1);

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