Our method applied to WASP-19 data. This is the same data as were used to test the PRISM code (Tregloan-Reed et al. 2013). Upper panel: observed light curves of three transit events shown as black dots, and the light curves produced by our recovered stellar maps is shown as solid lines. Bottom panel: recovered stellar maps. The left map corresponds to the red light curve in the upper panel. The central map corresponds to blue light curve, and the right map corresponds to the green light curve. Star spots were detected in the recovered maps from the first two transit events. The dashed red circle shows the size and position of the spots detected with the PRISM code.