Need help in saving a barcode as image

for (int i = 0; i < len; i++)
           {
               Rectangle rect = new Rectangle();
               rect.Height = 200;
               if (currentColor == 0)
               {
                   currentColor = 1;
                   rect.Fill = new SolidColorBrush(Colors.Black);

               }
               else
               {
                   currentColor = 0;
                   rect.Fill = new SolidColorBrush(Colors.White);

               }
               Canvas.SetLeft(rect, currentPos);
               Canvas.SetTop(rect, currentTop);

               if (outputString[i] == 't')
               {
                   rect.Width = thinWidth;
                   currentPos += thinWidth;

               }
               else if (outputString[i] == 'w')
               {
                   rect.Width = thickWidth;
                   currentPos += thickWidth;

               }
               mainCanvas.Children.Add(rect);

           }