Evolution of the IPCA with ARDI estimate through the iterations. The dataset used is the same as in Fig. 3. The first grid of plots (top) displays the final estimation segmented into patches of size 15 × 15 pixels. The second grid of plots (bottom) corresponds to the gradient computed within these patches according to Eq. 4. The red lines indicate the g_tol threshold at ±10⁻². If the threshold is reached, the curves are displayed in green, and a black dot indicates at which iteration the signal has converged. Otherwise, the curves are displayed in blue.