Image控件內容保存到本地文件并非占用：

其中ImageToSave是Wpf中的Image控件：

var encoder = new PngBitmapEncoder();
encoder.Frames.Add(BitmapFrame.Create((BitmapSource)this.ImageToSave.Source));
using (FileStream stream = new FileStream(sfd.FileName, FileMode.Create))
encoder.Save(stream);

從文件轉Image控件圖片并非占用：

//方法一：
            Stream s = File.Open(fileName, FileMode.Open);
            Image img = Bitmap.FromStream(s);
            s.Close();
            s.Dispose();
//方法二，封裝成函數：
        public static System.Drawing.Image LoadImage(string fileName)
        {
            FileStream fileStream = new FileStream(fileName, FileMode.Open, FileAccess.Read);
 
            int byteLength = (int)fileStream.Length;
            byte[] fileBytes = new byte[byteLength];
            fileStream.Read(fileBytes, 0, byteLength);
            fileStream.Close();
 
            return System.Drawing.Image.FromStream(new MemoryStream(fileBytes));
        }