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To correct for non-uniform lighting or unequal illumination on the left and
right sides of the face, we perform histogram fitting independently to
both of these components of the image. Thus, a dark left side of the face will
be brightened while a bright right side is simultaneously darkened. we
perform a split or ``windowed'' histogram analysis on two components separately:
the left side (l) and the right side (r) of the face. Two histograms,
Hl(i) and Hr(i), generate the two mapping functions:
for the left window and the right window
respectively. The windowing is shown in Figure .
Windowing to split face histogram correction for each side of the face.