title: Fast work with Bitmaps in C#
body: <p>I need to access each pixel of a Bitmap, work with them, then save them to a Bitmap.</p>
  
  <p>Using <code>Bitmap.GetPixel()</code> and <code>Bitmap.SetPixel()</code>, my program runs slowly.</p>
  
  <p>How can I quickly convert <code>Bitmap</code> to <code>byte[]</code> and back?</p>
  
  <p>I need a <code>byte[]</code> with <code>length = (4 * width * height)</code>, containing RGBA data of each pixel.</p>