title: convert 8 bit color bmp image to 8 bit grayscale bmp
body: <p>This is my bitmap object</p>
  
  <pre><code>Bitmap b = new Bitmap(columns, rows, PixelFormat.Format8bppIndexed);
  BitmapData bmd = b.LockBits(new Rectangle(0, 0, columns, rows), ImageLockMode.ReadWrite, b.PixelFormat);
  </code></pre>
  
  <p>How do i convert this into a 8 bit grayscale bitmap ?</p>