From Figure 1 it is obvious that HE cannot be used
directly for consumer video. The proposed method
presented here [7] uses HE in a controlled and localized
manner to stretch the details in dark images while
improving overall contrast in brighter ones. It is referred
to as Adaptive Contrast Enhancement (ACE) because of
the locally adaptive effect that is produced in each frame.
The proposed algorithm begins by dividing the histogram
of the luminance levels into three regions – dark, mid and
bright. These regions were of equal size. Each of these
three regions is then processed independently using HE.
The effect of HE is then toned down depending on the
shape of the histogram of each region. This independent
processing has two main advantages. Firstly, it brings out
the details in dark images while keeping brighter pixels
untouched. Dark images are much more common than
bright in consumer video and hence improving their
contrast is the most important application. Secondly it
has the ability to create a subtle yet desirable
enhancement without modifying the whole image too
much. Figure 2 shows the regions of the luminance range
that are used in the proposed method.