.net 上传图片压缩裁剪，压缩后大小一般不会变大

100

101

102

103

104

105

106

107

108

109

110

111

112

113

114

115

[HttpPost]
       [AuthorizeIgnore]
       public ActionResult PhoneUpload()
       {
           try
           {
               var files = Request.Files;
               if (files == null || files.Count == 0)
                   throw new Exception("请选择需要上传的图片");
 
               var upFile = files[0];
 
               var allowType = new string[] { "image/jpeg", "image/jpg", "image/png", "image/gif" };
               if (!allowType.Contains(upFile.ContentType))
                   throw new Exception("请上传“.jpg/.png/.gif”格式的图片");
 
               if (upFile.ContentLength > 1024 * 1024 * 20)
                   throw new Exception("图片大小不能超20M");
 
               string ext = upFile.FileName.Substring(upFile.FileName.LastIndexOf('.'));
 
               var guid = Guid.NewGuid();
               string strpath = Path.Combine("UploadFiles", "imagebanklog", guid + ext);
               string strpath_th = Path.Combine("UploadFiles", "imagebanklog", guid + "_th" + ext);
 
               string path = Path.Combine(Server.MapPath("~/"), strpath);
               string path_th = Path.Combine(Server.MapPath("~/"), strpath_th);
 
               upFile.SaveAs(path);
                 
               GetThumImage(path, 90, 1024, path_th);
               try
               {
                   System.IO.File.Delete(path);
               }
               catch { }
 
               return Json(new { id = 0, success = true, result = strpath_th }, "text/html");
 
           }
           catch (Exception ex)
           {
               return Json(new { id = 0, success = false, msg = ex.Message.ToString() }, "text/html");
           }
       }
       /// <summary>
       /// 生成缩略图
       /// </summary>
       /// <param name="sourceFile">原始图片文件</param>
       /// <param name="quality">质量压缩比,0-100,100是最清晰</param>
       /// <param name="width">最大宽度</param> 
       /// <param name="outputFile">输出文件名</param>
       /// <returns>成功返回true,失败则返回false</returns>
       private   bool GetThumImage(string sourceFile, long quality, int width, string outputFile)
       {
           try
           {
               long imageQuality = quality;
               Bitmap sourceImage = new Bitmap(sourceFile);
 
               var oWidth = sourceImage.Width;
               var oHeight = sourceImage.Height;
               var height = oHeight;
               if (width > oWidth)
               {
                   width = oWidth;
               }
               else
               {
                   height = width * oHeight / oWidth;
               }
                 
               var myImageCodecInfo = GetEncoderInfo("image/jpeg");
               var myEncoder = System.Drawing.Imaging.Encoder.Quality;
               var myEncoderParameters = new EncoderParameters(1);
               var myEncoderParameter = new EncoderParameter(myEncoder, imageQuality);
               myEncoderParameters.Param[0] = myEncoderParameter;
               float xWidth = sourceImage.Width;
               float yWidth = sourceImage.Height;
               Bitmap newImage = new Bitmap(width, height);
               Graphics g = Graphics.FromImage(newImage);
 
               g.DrawImage(sourceImage, 0, 0, width, height);
               g.Dispose();
               newImage.Save(outputFile, myImageCodecInfo, myEncoderParameters);
 
               sourceImage.Dispose();
               sourceImage = null;
               newImage.Dispose();
               newImage = null;
 
               return true;
           }
           catch
           {
               return false;
           }
 
       }
   
       /// <summary>
       /// 获取图片编码信息
       /// </summary>
       private static ImageCodecInfo GetEncoderInfo(String mimeType)
       {
           int j;
           ImageCodecInfo[] encoders;
           encoders = ImageCodecInfo.GetImageEncoders();
           for (j = 0; j < encoders.Length; ++j)
           {
               if (encoders[j].MimeType == mimeType)
                   return encoders[j];
           }
           return null;
       }