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% SIFTLOCALMAX Find local maximizers
% SEL=SIFTLOCALMAX(F) returns the indexes of the local maximizers of
% the Q-dimensional array F.
%
% A local maximizer is an element whose value is greater than the
% value of all its neighbors. The neighbors of an element i1...iQ
% are the subscripts j1...jQ such that iq-1 <= jq <= iq (excluding
% i1...iQ itself). For example, if Q=1 the neighbors of an element
% are its predecessor and successor in the linear order; if Q=2, its
% neighbors are the elements immediately to its north, south, west,
% est, north-west, north-est, south-west and south-est
% (8-neighborhood).
%
% Points on the boundary of F are ignored (and never selected as
% local maximizers).
%
% SEL=SIFTLOCALMAX(F,THRESH) accepts an element as a mazimizer only
% if it is at least THRES greater than all its neighbors.
%
% SEL=SIFTLOCALMAX(F,THRESH,P) look for neighbors only in the first
% P dimensions of the Q-dimensional array F. This is useful to
% process F in ``slices''.
%
% REMARK. Matrices (2-array) with a singleton dimension are
% interpreted as vectors (1-array). So for example SIFTLOCALMAX([0 1
% 0]) and SIFTLOCALMAX([0 1 0]') both return 2 as an aswer. However,
% if [0 1 0] is to be interpreted as a 1x2 matrix, then the correct
% answer is the empty set, as all elements are on the boundary.
% Unfortunately MATLAB does not distinguish between vectors and
% 2-matrices with a singleton dimension. To forece the
% interpretation of all matrices as 2-arrays, use
% SIFTLOCALMAX(F,TRESH,2) (but note that in this case the result is
% always empty!).
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