Fig. 1

The intensity normalization function for the histogram-based normalization phase. The first mapping is from [\( S_{1i} \), \( \mu_{i} \)] to [\( LIR \), \( \mu_{s} \)] and the second is from [\( \mu_{i} \), \( S_{2i} \)] to [\( \mu_{s} \), \( HIR \)]. The lower and the upper ends of the standard scale are subsequently extended to \( m^{\prime}_{1} \) and \( m^{\prime}_{2} \), respectively, by mapping [\( m_{1} \), \( S_{1i} \)] to [\( m^{\prime}_{1} \), \( LIR \)] and [\( S_{2i} \), \( m_{2} \)] to [\( HIR \), \( m^{\prime}_{2} \)].