Asp.net mvc 实时生成缩率图到硬盘

之前对于缩率图的处理是在图片上传到服务器之后，同步生成两张不同尺寸的缩率供前端调用，刚开始还能满足需求，慢慢的随着前端展示的多样化，缩率图已不能前端展示的需求，所以考虑做一个实时生成图片缩率图服务。

每次调用实时生成缩率图，不缓存着实有点浪费，所以在生成缩率的同时缓存到硬盘一份，效率提高很多。

之前从网上看了一下有人用nginx + lua实现的，效率那是没什么可说的，但是时间紧迫，自己也没时间去研究，所以暂时先用aps.net mvc4来实现一个，以后有时间了，再慢慢修改。

用自己熟悉的.net性能可能差那么一点点，但是实现速度快，保证可以在极端的时间内上线，并且在功能上更强。

思路很简单，就是根据请求，判断需要的缩率图是否已存在于硬盘上，如果有直接返回，没有则下载原图，并生成缩率图到本地，返回给客户端。

下面直接粘贴代码片段：

/// <summary>/// 生成图片缩率图Action/// </summary>/// <param name="p">原图url</param>/// <param name="id">图片尺寸以及生成缩率图的类型</param>/// <returns></returns>
        [HttpGet]public async Task<ActionResult> Index(string p, string id){if (string.IsNullOrEmpty(p)){return new HttpStatusCodeResult(404);}string oPath = Regex.Replace(p, @"http[s]?://(.*?)/", "/", RegexOptions.IgnoreCase);int? oWidth = 200, oHeight = 200;int cutMode = 3;string pPath;string oDir;if (!string.IsNullOrEmpty(id)){string[] ss = id.Split(new char[] { '_' }, StringSplitOptions.RemoveEmptyEntries);if (ss.Length < 2){return new HttpStatusCodeResult(404);}if (ss.Length > 2){cutMode = int.Parse(ss[2]);}oPath = oPath.Insert(oPath.LastIndexOf('/') + 1, string.Format("{0}_{1}_{2}_", ss[0], ss[1], cutMode));oWidth = int.Parse(ss[0]);oHeight = int.Parse(ss[1]);}pPath = Server.MapPath(oPath);oDir = Path.GetDirectoryName(pPath);if (!System.IO.File.Exists(pPath)){byte[] imagebytes =await FileHelper.DownLoadFileAsync(p);if (!Directory.Exists(oDir)){Directory.CreateDirectory(oDir);}FileHelper.MakeThumbnail(FileHelper.BytToImg(imagebytes), oWidth.Value, oHeight.Value, (ThumbnailMode)cutMode, pPath, true);}return File(pPath, FileHelper.GetContentTypeByExtension(Path.GetExtension(pPath).ToLower()));}

辅助方法：

 public class FileHelper{/// <summary>/// 图片后缀和ContentType对应字典/// </summary>static Dictionary<string, string> extensionContentTypeDic;static FileHelper(){if (extensionContentTypeDic == null){//.jpg", ".png", ".gif", ".jpegextensionContentTypeDic = new Dictionary<string, string>();extensionContentTypeDic.Add(".jpg", "image/jpeg");extensionContentTypeDic.Add(".png", "image/png");extensionContentTypeDic.Add(".gif", "image/gif");extensionContentTypeDic.Add(".jpeg", "image/jpeg");}}/// <summary>/// 根据后缀名获取extension/// </summary>/// <param name="extension"></param>/// <returns></returns>public static string GetContentTypeByExtension(string extension){if (extensionContentTypeDic.ContainsKey(extension)){return extensionContentTypeDic[extension];}return null;}///  <summary > /// 将Image对象转化成二进制流 ///  </summary > ///  <param name="image" > </param > ///  <returns > </returns > public static byte[] ImageToByteArray(Image image){MemoryStream imageStream = new MemoryStream();Bitmap bmp = new Bitmap(image.Width, image.Height);Graphics g = Graphics.FromImage(bmp);g.DrawImage(image, new System.Drawing.Rectangle(0, 0, image.Width, image.Height));try{bmp.Save(imageStream, image.RawFormat);}catch (Exception e){bmp.Save(imageStream, System.Drawing.Imaging.ImageFormat.Jpeg);}byte[] byteImg = imageStream.GetBuffer();bmp.Dispose();g.Dispose();imageStream.Close();return byteImg;}/// <summary> /// 字节流转换成图片 /// </summary> /// <param name="byt">要转换的字节流</param> /// <returns>转换得到的Image对象</returns> public static Image BytToImg(byte[] byt){MemoryStream ms = new MemoryStream(byt);Image img = Image.FromStream(ms);ms.Close();return img;}/// <summary>/// 生成缩率图/// </summary>/// <param name="originalImage">原始图片Image</param>/// <param name="width">缩率图宽</param>/// <param name="height">缩率图高</param>/// <param name="mode">生成缩率图的方式</param>/// <param name="thumbnailPath">缩率图存放的地址</param>public static Image MakeThumbnail(Image originalImage, int width, int height, ThumbnailMode mode, string thumbnailPath, bool isSave = true){int towidth = width;int toheight = height;int x = 0;int y = 0;int ow = originalImage.Width;int oh = originalImage.Height;switch (mode){case ThumbnailMode.HW://指定高宽缩放（可能变形）                  break;case ThumbnailMode.W://指定宽，高按比例                      toheight = originalImage.Height * width / originalImage.Width;break;case ThumbnailMode.H://指定高，宽按比例  towidth = originalImage.Width * height / originalImage.Height;break;case ThumbnailMode.Cut://指定高宽裁减（不变形）                  if ((double)originalImage.Width / (double)originalImage.Height > (double)towidth / (double)toheight){oh = originalImage.Height;ow = originalImage.Height * towidth / toheight;y = 0;x = (originalImage.Width - ow) / 2;}else{ow = originalImage.Width;oh = originalImage.Width * height / towidth;x = 0;y = (originalImage.Height - oh) / 2;}break;default:break;}//新建一个bmp图片  System.Drawing.Image bitmap = new System.Drawing.Bitmap(towidth, toheight);//新建一个画板  Graphics g = System.Drawing.Graphics.FromImage(bitmap);//设置高质量插值法  g.InterpolationMode = System.Drawing.Drawing2D.InterpolationMode.High;//设置高质量,低速度呈现平滑程度  g.SmoothingMode = System.Drawing.Drawing2D.SmoothingMode.HighQuality;//清空画布并以透明背景色填充  
            g.Clear(Color.Transparent);//在指定位置并且按指定大小绘制原图片的指定部分  g.DrawImage(originalImage, new Rectangle(0, 0, towidth, toheight),new Rectangle(x, y, ow, oh),GraphicsUnit.Pixel);if (!isSave){return bitmap;}try{//以jpg格式保存缩略图  //bitmap.Save(thumbnailPath, bitmap.RawFormat);
                bitmap.Save(thumbnailPath, ImageFormat.Jpeg);return bitmap;}catch (System.Exception e){throw e;}finally{originalImage.Dispose();bitmap.Dispose();g.Dispose();}return null;}/// <summary>/// 下载指定文件/// </summary>/// <param name="remoteUrl"></param>/// <param name="ss"></param>public static Task<byte[]> DownLoadFileAsync(string remoteUrl){WebClient wc = new WebClient();try{return wc.DownloadDataTaskAsync(remoteUrl);}catch (Exception e){throw new Exception("下载文件失败");}}}public enum ThumbnailMode{/// <summary>/// 指定高宽缩放（可能变形）/// </summary>
        HW,/// <summary>/// 指定高，宽按比例/// </summary>
        H,/// <summary>/// 指定宽，高按比例/// </summary>
        W,/// <summary>/// 指定高宽裁减（不变形）   /// </summary>
        Cut,}