To select the regions where extra relaxation will be applied, we propose approximating ΩE on each Ωhl by an index set Qhl whose entries point to pixels requiring additional smoothing steps. An easy way to construct such an index set for grid Ωhl is shown in Algorithm 5. Other more accurate methods using edge-detection techniques may be used as well. Basically this algorithm is used in the first leg of the very first FAS cycle (after step 2 in Algorithm 2). The scalar entry δ, in Algorithm 5, indicates the percentage of the domain to be overrelaxed, i.e.,edges. Since edges usually represent a small portion of the whole image, we suggest using δ < 0.2.