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Copyright Tristan Aubrey-Jones November 2006.
function beta = greedyice_choosebeta(con, im, beta)
% GREEDYICE_CHOOSEBETA Relaxes values of beta at contour corners
%% constants
threshold1 = 0.25; %% corner curvature threshold 29 degrees
threshold2 = 0.4; %% corner edge strength threshold
%% init
n = length(con);
vlast = con(n,:)';
curvatures = zeros(n,1);
%% calculate curvature at each point on contour
for i = 1:n
%% get this and next point
vi = con(i,:)';
if i == n, vnext = con(1,:)';
else vnext = con(i+1,:)'; end
%% calculate vectors
ui = vi - vlast;
unext = vnext - vi;
%% calculate curvature (avoid divide by zero)
if unext == 0
if ui == 0
ci = 0;
else
ci = norm((ui / norm(ui)) - 0) ^ 2;
end
else
if ui == 0
ci = norm(0 - (unext / norm(unext))) ^ 2;
else
ci = norm((ui / norm(ui)) - (unext / norm(unext))) ^ 2;
end
end
curvatures(i) = ci;
vlast = vi;
end
%% process to determine whether to allow corners on next iteration
clast = curvatures(n);
for i = 1:n
ci = curvatures(i);
if i == n, cnext = curvatures(1);
else cnext = curvatures(i+1); end
vi = con(i,:)';
if ci > clast && ci > cnext
if ci > threshold1 && im(vi(1), vi(2)) < threshold2
beta(i) = 0;
end
end
clast = ci;
end