function Y = fuse_rat(M1, M2, zt, ap, mp)%Y = fuse_rat(M1, M2, zt, ap, mp) image fusion with ratio pyramid%%    M1 - input image A%    M2 - input image B%    zt - maximum decomposition level%    ap - coefficient selection highpass (see selc.m) %    mp - coefficient selection base image (see selb.m) %%    Y  - fused image   %    (Oliver Rockinger 16.08.99)% check inputs [z1 s1] = size(M1);[z2 s2] = size(M2);if (z1 ~= z2) | (s1 ~= s2)  error('Input images are not of same size');end;% define filter w  = [1 4 6 4 1] / 16;% define epseps = 1e-6;% cells for selected imagesE = cell(1,zt);% loop over decomposition depth -> analysisfor i1 = 1:zt   % calculate and store actual image size   [z s]  = size(M1);   zl(i1) = z; sl(i1)  = s;    % check if image expansion necessary   if (floor(z/2) ~= z/2), ew(1) = 1; else, ew(1) = 0; end;  if (floor(s/2) ~= s/2), ew(2) = 1; else, ew(2) = 0; end;  % perform expansion if necessary  if (any(ew))  	M1 = adb(M1,ew);  	M2 = adb(M2,ew);  end;	    % perform filtering   G1 = conv2(conv2(es2(M1,2), w, 'valid'),w', 'valid');  G2 = conv2(conv2(es2(M2,2), w, 'valid'),w', 'valid');   % decimate, undecimate and interpolate   M1T = conv2(conv2(es2(undec2(dec2(G1)), 2), 2*w, 'valid'),2*w', 'valid');  M2T = conv2(conv2(es2(undec2(dec2(G2)), 2), 2*w, 'valid'),2*w', 'valid');   % select coefficients and store them  E(i1) = {selc(M1./(M1T+eps), M2./(M2T+eps), ap)};    % decimate   M1 = dec2(G1);  M2 = dec2(G2);end;% select base coefficients of last decompostion stageM1 = selb(M1,M2,mp);% loop over decomposition depth -> synthesisfor i1 = zt:-1:1  % undecimate and interpolate   M1T = conv2(conv2(es2(undec2(M1), 2), 2*w, 'valid'), 2*w', 'valid');  % add coefficients  M1  = (M1T+eps) .* E{i1};  % select valid image region   M1 	= M1(1:zl(i1),1:sl(i1));end;% copy imageY = M1;