1. Bitmap to ImageSource
   将得到的Bitmap对象转换为wpf常用的Imagesource对象

BitmapSource bs = Imaging.CreateBitmapSourceFromHBitmap(bmp.GetHbitmap(), IntPtr.Zero, Int32Rect.Empty, BitmapSizeOptions.FromEmptyOptions());

得到的BitmapSource是Imagesource的子类

1. ImageSource to Bitmap

首先得到ImageSource对象_imagesource

System.IO.MemoryStream ms = new System.IO.MemoryStream();
BmpBitmapEncoder encoder = new BmpBitmapEncoder();
encoder.Frames.Add(BitmapFrame.Create((BitmapSource)_imagesource));
encoder.Save(ms);

Bitmap bp = new Bitmap(ms);
ms.Close();