follow - A contour follower
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. That is, (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).
initial_dir = PWD; chdir (SIPDIR + 'images'); Img = imread('star.bmp'); xset('window',0) xbasc() imshow(Img,2); [x,y] = follow(Img); xset('window',1) xbasc() plot2d(1:size(x,'*'),x,2); plot2d(1:size(y,'*'),y,1); chdir(initial_dir);
http://siptoolbox.sourceforge.net