private BitmapSource CombineImage(BitmapSource img1,BitmapSource img2)
{
   var composeImg = new RenderTargetBitmap(img1.PixelWidth,
     img1.PixelHeight+img2.PixelHeight,
     img1.DpiX,
     img1.DpiY,
     PixelFormat.Default );
 
   var dv = new DrawingVisual();
   using(var dc = dv.RenderOpen())
    {
       dc.DrawImage(img1,
 
new Rect(0,0,img1.PixelWidth,img1.PixelHeight));
       dc.DrawImage(img1,new Rect(0,0,img2.PixelWidth,img2.PixelHeight));

       composeImg.Render(dv);
    }

   return composeImg;
}      

C# 合並兩張圖片