Fig. 13 shows the comparisons of average threshold value
difference of adaptive segmentation procedure using different
operational sub-image sizes and interpolation grid
sizes. The threshold value maps created by different combinations
of sub-image sizes and interpolation sizes were
compared with the reference threshold value map created
by using 32×32 operational sub-image and without interpolation
(1×1 interpolation grid size). The average threshold
value difference was calculated by taking the average of the
absolute difference of the threshold values of each corresponding
pixels of the two threshold value map. Although
the average difference slightly increases with the increase
of the interpolation grid size, the difference is not significant.
The maximum average difference of threshold value
maps for all cases is less than five grey levels, which indicates
that the threshold value map is relatively stable regardless
of the variations in sub-image size or interpolation grid
size