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1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 | % VL_LOCALMAX Find local maximizers
% SEL=VL_LOCALMAX(F) returns the indexes of the local maximizers of
% the Q-dimensional array F.
%
% A local maximizer is an array element whose value is larger than
% the value of all its neighbors. The neighbors of an element
% i1...iQ have 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=VL_LOCALMAX(F,THRESH) accepts an element as a mazimizer only
% if it is not smaller than THRESH.
%
% SEL=VL_LOCALMAX(F,THRESH,P) looks for neighbors only in the first
% P dimensions of the Q-dimensional array F. This allows to process
% F in ``slices''.
%
% Remark::
% Matrices (2-array) with a singleton dimension are
% interpreted as vectors (1-array). So for example VL_LOCALMAX([0 1
% 0]) and VL_LOCALMAX([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
% VL_LOCALMAX(F,TRESH,2) (but note that in this case the result is
% always empty!).
%
% See also: VL_HELP().
% Copyright (C) 2007-12 Andrea Vedaldi and Brian Fulkerson.
% All rights reserved.
%
% This file is part of the VLFeat library and is made available under
% the terms of the BSD license (see the COPYING file).
% TODO: Companion REFINELOCALMAX
% TODO: Do something smarter at boundaries
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