Active Contour Toolbox
05 Jul 2006
05 Jul 2006)
This toolbox provides some functions to segment an image or a video using active contours
|po_square(center, width, tilt, number_of_edges, resolution)
function square = po_square(center, width, tilt, number_of_edges, resolution)
%po_square: instantiation of a closed polygon sampling a square
% p = po_square(c, w, t, n, s) computes a closed polygon sampling the square
% of center c, width w, and tilt angle t with either n regularly spaced
% vertices (or equivalently n edges) or a vertex every s pixels. Resolution s
% is used unless n is strictly greater than 3. s does not have to be an
% integer. If n is strictly greater than 3, then it must be equal to 4*i for
% an integer i.
% t is in degrees.
%See also polygon.
%Polygon Toolbox by Eric Debreuve
%Last update: June 13, 2006
if number_of_edges > 3
resolution = 4 * width / number_of_edges;
half_width = width / 2;
width = round(width / resolution);
if width <= 0
square = ;
horizontal_side = resolution * (width:-1:0) - half_width;
vertical_side = horizontal_side(2:end-1);
horizontal_side(1) = half_width;
square = [vertical_side, zeros(1,width + 1) - half_width, ...
fliplr(vertical_side), half_width * ones(1,width + 1); ...
half_width * ones(1, width - 1), horizontal_side, ...
zeros(1, width - 1) - half_width, fliplr(horizontal_side); ...
ones(1, 4 * width)];
tilt = tilt * pi / 180;
cos_of_tilt = cos(tilt);
sin_of_tilt = sin(tilt);
in_place = [cos_of_tilt, - sin_of_tilt, center(1); ...
sin_of_tilt, cos_of_tilt, center(2)];
square = in_place * square;
square = [square(:,end) square];