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_rectangle(center, lengths, tilt, number_of_edges, resolution)
function rectangle = po_rectangle(center, lengths, tilt, number_of_edges, resolution)
%po_rectangle: instantiation of a closed polygon sampling a rectangle
% p = po_rectangle(c, l, t, n, s) computes a closed polygon sampling the
% rectangle of center c, lengths l, 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
% 2*(i+j) for some integers i and j.
% l can be a 1x2 or a 2x1 matrix. t is in degrees.
%See also polygon.
%Polygon Toolbox by Eric Debreuve
%Last update: June 13, 2006
if number_of_edges > 3
resolution = 2 * sum(lengths) / number_of_edges;
half_lengths = lengths / 2;
lengths = round(lengths / resolution);
if any(lengths <= 0)
rectangle = ;
horizontal_side = resolution * (lengths(2):-1:0) - half_lengths(2);
horizontal_side(1) = half_lengths(2);
vertical_side = resolution * (lengths(1)-1:-1:1) - half_lengths(1);
rectangle = [vertical_side, zeros(1,lengths(2) + 1) - half_lengths(1), ...
fliplr(vertical_side), half_lengths(1) * ones(1,lengths(2) + 1); ...
half_lengths(2) * ones(1, lengths(1) - 1), horizontal_side, ...
zeros(1, lengths(1) - 1) - half_lengths(2), fliplr(horizontal_side); ...
ones(1, 2 * sum(lengths))];
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)];
rectangle = in_place * rectangle;
rectangle = [rectangle(:,end) rectangle];