Figure 1. Examples of surrogates for images with increasing degree of autocorrelation.

The first row features particular simulations of fractal patterns (fractional Brownian field) generated by Fourier synthesis [27] for four degrees of autocorrelation (from short- to long-ranged as indirectly quantified by the β 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).