title: histogram equalization transformation function
body: <p>Suppose that a given 3-bit image(L=8) of size 64*64 pixels (M*N=4096) has the intensity distribution shown as below. How to obtain histogram equalization transformation function 
  and then compute the equalized histogram of the image?</p>
  
  <pre><code>Rk     nk
  0      800
  1      520
  2      970 
  3      660
  4      330
  5      450
  6      260
  7      106
  </code></pre>