title: Graphic transformations
body: <p>I'm working with data (stuff like Sin/Cosin waves, etc) that repeat with frequency M.
  I've written a simple display control where it takes the data and paints connected lines to represent the data in a pretty picture.</p>
  
  <p>My question is, the data is given where if painted onto a bitmap, quadrant 1 data is in quadrant 3 and quadrant 2 data is in quadrant 4 (and vice versa).</p>
  
  <p>The bitmap is of width M and hight <code>array.Max - array.Min</code>.</p>
  
  <p>Is there a simple transform for changing the data so it will display in the appropriate quadrants?</p>