高强度不失真在线压缩图片（jpg与png）

 [HttpPost]         public ApiResult ImageCompress(GeneralImageCompressViewModel vm)         {             if (!ModelState.IsValid) { return this.ModelErrorTextResult(); }               int quality = 80;             if (vm.QualityType == 1) { quality = 80; }             else if (vm.QualityType == 2) { quality = 60; }             else if (vm.QualityType == 3) { quality = 40; }             else if (vm.QualityType == 4) { quality = 20; }             string fileName = Path.GetFileNameWithoutExtension(vm.ImageUrl);             string targetUrl = vm.ImageUrl.Replace(fileName, $"{fileName}_compress_{quality}");              string extName = Path.GetExtension(vm.ImageUrl).Replace(".", "").ToLower();             string sourceFullName = UrlOper.MapPath(vm.ImageUrl);             string targetFullName = UrlOper.MapPath(targetUrl);              bool isSuccess = true;             Size newSize = new Size();             try             {                 using (Image img = Image.FromFile(sourceFullName))                 {                     newSize = Commons.EqualRatioSize(img.Width, img.Height, vm.ImgWidth, vm.ImgHeight);                     using (var bmp = new Bitmap(img, newSize.Width, newSize.Height))                     {                         //压缩PNG                         if (extName == "png")                         {                             string tmpImg = UrlOper.MapPath(vm.ImageUrl.Replace(fileName, $"{fileName}_pngsitesize_{newSize.Width}_{newSize.Height}"));                             bmp.Save(tmpImg);                             bmp.Dispose();                              var pngCompressor = new PNGCompression.PNGCompressor                             {                                 PNGToolPath = UrlOper.MapPath("~/content/tools/pngquant"),                                 PNGExeName = "pngquant.exe"                             };                             pngCompressor.CompressImageLossy(tmpImg, targetFullName, new PNGCompression.LossyInputSettings                             {                                 MinQuality = 0,                                 MaxQuality = (quality + 20)                             });                              System.IO.File.Delete(tmpImg);                         }                         //压缩JPG                         else if (extName == "jpg" || extName == "jpeg")                         {                             var jpgCompressor = new MozJpegSharp.TJCompressor();                             var compressed = jpgCompressor.Compress(bmp, MozJpegSharp.TJSubsamplingOption.Chrominance420, quality, MozJpegSharp.TJFlags.None);                             System.IO.File.WriteAllBytes(targetFullName, compressed);                         }                     }                 }                 if (!System.IO.File.Exists(targetFullName))                 {                     isSuccess = false;                 }             }             catch             {                 isSuccess = false;             }             if (!isSuccess)             {                 return this.Ok(new                 {                     IsCompressOK = false                 });             }              long sourceLength = new System.IO.FileInfo(sourceFullName).Length;             long targetLength = new System.IO.FileInfo(targetFullName).Length;             //如果压缩后更大，则返回原图             if (targetLength > sourceLength)             {                 targetLength = sourceLength;                 targetUrl = vm.ImageUrl;             }              var compressRatio = 100 - (int)(((decimal)targetLength / (decimal)sourceLength) * 100m);             if (compressRatio == 100) { compressRatio = 99; }             string sourceSizeDesc = FileHelper.GetFileSizeDesc(sourceLength);             string targetSizeDesc = FileHelper.GetFileSizeDesc(targetLength);             object result = new             {                 Source = UrlOper.ResolveClientUrl(vm.ImageUrl),                 Target = targetUrl,                 IsCompressOK = true,                 ImgWidth = newSize.Width,                 ImgHeight = newSize.Height,                 SourceSizeDesc = sourceSizeDesc,                 TargetSizeDesc = targetSizeDesc,                 CompressRatio = compressRatio             };              return this.Ok(result);         }