[WP7] ToByteArray

// Declare inside a static class 
public static class ExtensionMethods
{
   public static byte[] ToByteArray(this WriteableBitmap bmp)
   {
       // Init buffer
       int w = bmp.PixelWidth;
       int h = bmp.PixelHeight;
       int[] p = bmp.Pixels;
       int len = p.Length;
       byte[] result = new byte[4 * w * h];

       // Copy pixels to buffer
       for (int i = 0, j = 0; i < len; i++, j += 4)
       {
          int color = p[i];
          result[j + 0] = (byte)(color >> 24); // A
          result[j + 1] = (byte)(color >> 16); // R
          result[j + 2] = (byte)(color >> 8);  // G
          result[j + 3] = (byte)(color);       // B
        }

          return result;
    }
 }