Image Processing Reference
Fig. 4.11 The histograms of a color image
Fig. 4.12 The concept of histogram stretching
We obtain this by mapping the left-most non-zero bin in the histogram to 0 and the
right-most non-zero bin to 255, see Fig. 4.12 .
We can see that the histogram has been stretched so that the very dark and very
bright values are now used. It should also be noted that the distance between the
different bins is increased, hence the contrast is improved. This operation is denoted
histogram stretching and the algorithm is exactly the same as Eq. 4.3 with a and b
defined as in Eq. 4.4 . f 1 is the left-most non-zero bin in the histogram and f 2 is the
right-most non-zero bin in the histogram of the input image.