minmag.m

function z = minmag(c)
%MINMAG Finds the integer of minimum magnitude in a chain code.
%   Z = MINMAG(C) finds the integer of minimum magnitude in a given
%   4- or 8-connected Freeman chain code, C. The code is assumed to
%   be a 1-by-np array.

% The integer of minimum magnitude starts with min(c), but there
% may be more than one such value. Find them all,
I = find(c == min(c));
% and shift each one left so that it starts with min(c).
J = 0;
A = zeros(length(I), length(c));
for k = I;
   J = J + 1;
   A(J, :) = circshift(c,[0 -(k-1)]);
end

% Matrix A contains all the possible candidates for the integer of
% minimum magnitude. Starting with the 2nd column, succesively find
% the minima in each column of A. The number of candidates decreases
% as the seach moves to the right on A.  This is reflected in the
% elements of J.  When length(J)=1, one candidate remains.  This is
% the integer of minimum magnitude.
[M, N] = size(A);
J = (1:M)';
for k = 2:N
   D(1:M, 1) = Inf;
   D(J, 1) = A(J, k);
   amin = min(A(J, k));
   J = find(D(:, 1) == amin);
   if length(J)==1
      z = A(J, :);
      return
   end
end