| curvature - curvature of a contour |
K = curvature(BW [,sigma, delta]) K = curvature(x,y [,sigma, delta]) |
| K |
| vector containing the curvature of the contour at each point. |
| BW |
| Binary image containing only one object (0 for background, 1 for object). |
| x and y |
| vectors, storing the parametrized contour. |
| sigma |
| standard deviation of the gaussian function used to smooth the contour before computing the curvature. Defaults to 5. |
| delta |
| a double number, the time between samples (delta t), and defaults to 1. |
| Function curvature calculates the curvature at each point of a binary contour, using FFT and a formula from differential geometry. |
initial_dir = PWD;
chdir (SIPDIR + 'images');
Img = imread('star.bmp');
xbasc()
imshow(Img,2);
k = curvature(Img,13); // 13 sigma (shape is smoothed so curvature exists)
xbasc()
plot(k)
//
// observe there are six curvature peaks,
// corresponding to the six peaks of the star. There
// is one peak half at 0 and half at about 450.
// That's because the parametrization of
// the contour started at the highest peak and
// terminated there. Note also that the shape had to
// be considerably smoothed so the curvature doesn't
// blow up at the very sharp peaks of the star.
//
chdir(initial_dir);
|
| "Shape Analysis and Classification", L. da F. Costa and R. M. Cesar Jr., CRC Press, pp. 335-347. |
| "Differential Geometry of Curves and Surfaces", Manfredo P. do Carmo, Prentice Hall, 1976. |
| Ricardo Fabbri <rfabbri@if.sc.usp.br> |
| The latest version of the Scilab Image Processing toolbox can be found at |
| http://siptoolbox.sourceforge.net |
| follow, gsm, fftderiv |