rankmd.m

基于小波变换的特征检索算法

function rr = rankmd(ms, ics, ns)
% RANKMD Rank relevent images using Mahanalobis distance
%
% Input:
%	ms:	feature sets, one column per image
%	ics:	inverse covariance matrices (one page per image)
%	ns:	(optional), number of subimages per texture class
%		(default 16)
%
% Output:
%	rr:	rank of relevant images, one column for each query

if nargin < 3
    ns = 16;
end

nimages = size(ms, 2);

rr = zeros(ns, nimages);
copies = zeros(1, nimages);
ii = 1:nimages;

for q = 1:nimages			% each query			
    % Compute distances of each image in the database to the query
    z = ms - ms(:, q+copies);
    z = z';
    
    d = sum(z * ics(:,:,q) .* z, 2); 
    
    % Sort distances in ascending order
    [sd, si] = sort(d);

    % Find the rank of the images
    r(si) = ii;
    
    % Save the ranks of the relevant images
    c = floor((q-1) / ns);
    rr(:, q) = r((c*ns+1):((c+1)*ns))';
end