basis.m

jpeg的matlab代码

% basis - calculate basis matrices
%
% SYNOPSIS
%	basis(v, u)
%	basis(v, u, N)
%
% DESCRIPTION
% 	basis finds the (v,u) basis matrix of size NxN.
%       N defaults to 8.
%
% SEE ALSO
% 	basisgrid, psum, psumgrid

% Copyright (C) 1995-1997 Darrel Hankerson and Greg A. Harris
%
% This file is part of the JPEGtool collection of scripts for Octave
% and Matlab; see http://www.dms.auburn.edu/compression
%
% The JPEGtool collection is free software; you can redistribute it
% and/or modify it under the terms of the GNU General Public License
% as published by the Free Software Foundation; either version 2, or
% (at your option) any later version.
%
% The collection is distributed in the hope that it will be useful,
% but WITHOUT ANY WARRANTY; without even the implied warranty of
% MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
% GNU General Public License for more details.
%
% You should have received a copy of the GNU General Public License
% along with this package; see the file COPYING.  If not, write to the
% Free Software Foundation, 59 Temple Place - Suite 330, Boston, MA
% 02111-1307, USA.

function B = basis(v, u, N)

if ~exist('N')
  N = 8;
end

t = (1:2:2*N)*pi/(2*N);

B = cos(t*(v-1))' * cos(t*(u-1));