about interpolation

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li
li 2011-2-16
currently I am working on intepolation, after that I have to reconstruct a few images back into a higher resolution image. as describe here this is the tool http://www.flickr.com/photos/58977081@N02/5449868602/ and this is the intepolation method http://www.flickr.com/photos/58977081@N02/5447602298/ code about intepolation
//CODE intepolation
function rec = interpolation(s,delta_est,phi_est,factor)
n=length(s);
ss = size(s{1});
if (length(ss)==2) ss=[ss 1]; end
center = (ss+1)/2;
phi_rad = phi_est*pi/180;
% compute the coordinates of the pixels from the N images, using DELTA_EST and PHI_EST
for k=1:ss(3) % for each color channel
for i=1:n % for each image
s_c{i}=s{i}(:,:,k);
s_c{i} = s_c{i}(:);
r{i} = [1:factor:factor*ss(1)]'*ones(1,ss(2)); % create matrix with row indices
c{i} = ones(ss(1),1)*[1:factor:factor*ss(2)]; % create matrix with column indices
r{i} = r{i}-factor*center(1); % shift rows to center around 0
c{i} = c{i}-factor*center(2); % shift columns to center around 0
coord{i} = [c{i}(:) r{i}(:)]*[cos(phi_rad(i)) sin(phi_rad(i)); -sin(phi_rad(i)) cos(phi_rad(i))]; % rotate
r{i} = coord{i}(:,2)+factor*center(1)+factor*delta_est(i,1); % shift rows back and shift by delta_est
c{i} = coord{i}(:,1)+factor*center(2)+factor*delta_est(i,2); % shift columns back and shift by delta_est
rn{i} = r{i}((r{i}>0)&(r{i}<=factor*ss(1))&(c{i}>0)&(c{i}<=factor*ss(2)));
cn{i} = c{i}((r{i}>0)&(r{i}<=factor*ss(1))&(c{i}>0)&(c{i}<=factor*ss(2)));
sn{i} = s_c{i}((r{i}>0)&(r{i}<=factor*ss(1))&(c{i}>0)&(c{i}<=factor*ss(2)));
end
s_ = []; r_ = []; c_ = []; sr_ = []; rr_ = []; cr_ = [];
for i=1:n % for each image
s_ = [s_; sn{i}];
r_ = [r_; rn{i}];
c_ = [c_; cn{i}];
end
clear s_c r c coord rn cn sn
h = waitbar(0.5, 'Image Reconstruction');
set(h, 'Name', 'Please wait...');
% interpolate the high resolution pixels using cubic interpolation
rec_col = griddata(c_,r_,s_,[1:ss(2)*factor],[1:ss(1)*factor]','cubic',{'QJ'}); % option QJ added to make it work
rec(:,:,k) = reshape(rec_col,ss(1)*factor,ss(2)*factor);
end
rec(isnan(rec))=0;
close(h);
//ENDintepolation am I going on the right direction ?thanks

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回答（1 个）

Jan
Jan 2011-2-16
What is the "right direction"? Does you program created the wanted results?
Some parts are inefficient:
r{i} = [1:factor:factor*ss(1)]'*ones(1,ss(2));
Faster:
tmp = transpose(1:factor:factor*ss(1));
r{i} = tmp(:, ones(1, ss(2)));
Operating on cell elements is much slower than on an array. So I'd create temporary arrays at first and store them in the cells at the end only.
The square brackets around a vector are not needed and waste time: [1:n] => (1:n)

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