title: Inversion of a discrete function function.
body: <p>I have a table about inverse gamma correction these are the values coresponding from 0 to 256 down there. I need a way to calculate the inverse of this function -> something like 0, 2, 6, 9, ...</p>
  
  <p>I would appreciate it, if someone could tell me a freeware tool that could do that or an algorithm I could write in C.</p>
  
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