title: Why is .NET `PixelFormat` has an `Format8bppIndexed` element?
body: <p>A group of 8 bits can store 256 values.</p>
  
  <p>A gray level can have 256 variations.</p>
  
  <p>So, why do they need <code>Format8bppIndexed</code>? Why is it <code>Indexed</code>?</p>
  
  <p>Why not <code>Format8bpp</code> ?</p>