daniele@160: function D = dctmatrix(N,K,type)
daniele@160: 
daniele@160: error(nargchk(1,3,nargin,'struct'));
daniele@160: if ~exist('type','var') || isempty(type), type='II'; end
daniele@160: if ~exist('K','var') || isempty(K), K=N; end
daniele@160: 
daniele@160: [c r] = meshgrid(0:K-1,0:N-1);
daniele@160: switch type
daniele@160:     case 'I'
daniele@160:         D = cos(pi*c.*r/(K-1));
daniele@160:         D(1,:) = D(1,:)/sqrt(2);
daniele@160:         D(end,:) = D(end,:)/sqrt(2);
daniele@160:     case 'II'
daniele@160:         D = cos(pi*(2*c+1).*r/(2*K));
daniele@160:         D(1,:) = D(1,:)/sqrt(2);
daniele@160:     case 'III'
daniele@160:         D = cos(pi*(2*r+1).*c/(2*K));
daniele@160:         D(:,1) = D(:,1)/sqrt(2);
daniele@160:     case 'IV'
daniele@160:         D = cos(pi*(2*r+1+2*c+4*c.*r)/(4*K));
daniele@160:     otherwise
daniele@160:         error('unsupported dct type');
daniele@160: end
daniele@160: D = normcol(D);