Contrast shaping methods work by calculating an inputoutput
luminance curve defined at every luminance level.
The shape of the curve must depend on the statistics of
the video frame being processed. For example, dark
images would have a dark stretch curve applied to them.
Examples of this type of approach can be found in [1],
[2] and [3]. In a video system which has a gamma look
up table (LUT), the LUT has been used to implement the
contrast look up function. Although contrast shaping
methods are the most popular methods used in the
consumer electronics industry, they cannot provide a
localized contrast enhancement which is desirable. For
example, when a dark stretch is performed, bright pixels
become brighter. However a better way to enhance
darker images is to stretch and enhance the dark regions,
while leaving brighter pixels untouched.