F_paeth
case F_paeth : cur[k] = (uint8) (raw[k] + paeth(0,prior[k],0)); break;
CASE(F_paeth) cur[k] = (uint8) (raw[k] + paeth(cur[k-img_n],prior[k],prior[k-img_n]));
CASE(F_paeth) cur[k] = (uint8) (raw[k] + paeth(cur[k-out_n],prior[k],prior[k-out_n]));