Examples of surrogates for images with increasing degree of autocorrelation.

<p>The first row features particular simulations of fractal patterns (fractional Brownian field) generated by Fourier synthesis <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0048766#pone.0048766-Keitt2" target="_blank">[27]</a> for four degrees of autocorrelation (from short- to long-ranged as indirectly quantified by the <i>β</i> parameter). The following rows (2 to 5) display one particular random realization (i.e. re-simulation) of each of these fractal patterns according to four surrogate producing methods (random reassignments, random shifts, iterative amplitude adjusted Fourier transform (IAAFT) and wavelet-based energy synthesis, respectively).