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executable file 37 lines (27 sloc) 843 Bytes
% IM = mkFract(SIZE, FRACT_DIM)
%
% Make a matrix of dimensions SIZE (a [Y X] 2-vector, or a scalar)
% containing fractal (pink) noise with power spectral density of the
% form: 1/f^(5-2*FRACT_DIM). Image variance is normalized to 1.0.
% FRACT_DIM defaults to 1.0
% Eero Simoncelli, 6/96.
%% TODO: Verify that this matches Mandelbrot defn of fractal dimension.
%% Make this more efficient!
function res = mkFract(dims, fract_dim)
if (exist('fract_dim') ~= 1)
fract_dim = 1.0;
end
res = randn(dims);
fres = fft2(res);
sz = size(res);
ctr = ceil((sz+1)./2);
shape = ifftshift(mkR(sz, -(2.5-fract_dim), ctr));
shape(1,1) = 1; %%DC term
fres = shape .* fres;
fres = ifft2(fres);
if (max(max(abs(imag(fres)))) > 1e-10)
error('Symmetry error in creating fractal');
else
res = real(fres);
res = res / sqrt(var2(res));
end