wave2_nla.m

脊波工具和相关实验以及有关实验数据

function imrec = wave2_nla(im, wname, nlev, ncoefs, plotflag)
% WAVE2_NLA  Non-linear approximation using 2-D wavelet transform
%
%	imrec = wave2_nla(im, wname, nlev, ncoefs, [plotflag])

edge = 'per';
st = dwtmode('status', 'nodisp');
if ~strcmp(st, edge)
    dwtmode(edge);
end

% Wavelet transform
[c, s] = wavedec2(im, nlev, wname);

% Sort the coefficients in descending order of the magnitude
csort = sort(abs(c(:)));
csort = flipud(csort);

lk = length(ncoefs);
imrec = cell(1, lk);

% Non-linear or N-best terms approximation
for k = 1:lk
    cn = c .* (abs(c) >= csort(ncoefs(k)));    
    
    % Reconstruct with the most significant coefficients
    imrec{k} = waverec2(cn, s, wname);
end

if exist('plotflag', 'var')    
    clf;
    
    range = [-0.25, 1.25];
    % range = [-.5, 1.25];  
    colormap('gray');
    
    ssize = round(sqrt(lk));

    for k = 1:lk
	% subplot(ssize, ssize, k);
	subplot(1, lk, k);
	imagesc(imrec{k}, range);
	axis image,
	axis off,
	set(gca, 'FontSize', 8);        
	title(sprintf('%d coefficients\n(SNR =  %.2f dB)', ...
		      ncoefs(k), SNR(im, imrec{k})), 'FontSize', 9);

	% imr = im - imrec;
	% subplot(2, lk, lk + k);
	% imagesc(imr, range);
	% axis image
	% set(gca, 'FontSize', 8);    
	% title('Residue', 'FontSize', 10);
    end
end