从网络中获取图片显示到Image控件并保存到磁盘

一、从网络中获取图片信息：

  /// <summary>
        /// 获取图片
        /// </summary>
        /// <param name="url">Url</param>
        /// <returns>BitmapImage</returns>
        public BitmapImage GetImage(string url)
        {
            BitmapImage image=null;
            try
            {
                image = new BitmapImage();
                long fileLength = 0;
                //从url指定的网络地址获取图片信息
                WebRequest webReq = WebRequest.Create(url);
                WebResponse webRes = webReq.GetResponse();
                fileLength = webRes.ContentLength;
                Stream srm = webRes.GetResponseStream();
                byte[] bufferbyte = new byte[fileLength];
                int allByte = (int) bufferbyte.Length;
                int startByte = 0;
                while (fileLength > 0)
                {
                    int downByte = srm.Read(bufferbyte, startByte, allByte);
                    if (downByte == 0)
                    {
                        break;
                    }
                    startByte += downByte;
                    allByte -= downByte;
                }
                //以流的形式初始化图片                                                                                                 
                image.BeginInit();
                image.StreamSource = new MemoryStream(bufferbyte);
                image.EndInit();
                srm.Close();
                webRes.Close();
            }
            catch (Exception)
            {
                Console.WriteLine("获取图片信息失败");
            }
            return image;
        }

二、在Image控件中显示获取到的图片

  public void ShowImage(BitmapImage img)
        {
            image.Source = img;
            image.Width = img.PixelWidth;
            image.Height = img.PixelHeight;
        }

image是Image控件

三、保存Image到磁盘

 /// <summary>
        /// 保存图片到磁盘
        /// </summary>
        /// <param name="img"></param>
        public void SaveImage(Image img)
        {
            //img为Image控件
            BitmapSource bsrc = (BitmapSource)img.Source;
            //保存文件对话框
            SaveFileDialog sf = new SaveFileDialog();
            //设定默认保存类型为Png
            sf.DefaultExt = ".png";
            //指定用户只能下载jpg和png格式的图片
            sf.Filter = "JPG 图片 (*.jpg)|*.jpg|PNG 图片 (*.png)|*.png";
            if (sf.ShowDialog() == true)
            {
                PngBitmapEncoder pngE = new PngBitmapEncoder();
                pngE.Frames.Add(BitmapFrame.Create(bsrc));
                using (Stream stream = File.Create(sf.FileName))
                {
                    pngE.Save(stream);
                }
            }
        }