private void SaveThumbnail(Bitmap bitmap, int width, int height, string directory, string filename, string extension)
{var physicalPath = directory + filename + extension;using (var thumbnail = bitmap.GetThumbnailImage(width, height, () => { return true; }, IntPtr.Zero)){using (var encoderParameters = new EncoderParameters(1)){encoderParameters.Param[0] = new EncoderParameter(Encoder.Quality, 100L);thumbnail.Save(physicalPath,ImageCodecInfo.GetImageEncoders().Where(x => x.FilenameExtension.Contains(extension.ToUpperInvariant())).FirstOrDefault(),encoderParameters);}}
}

private void SaveThumbnail(Bitmap originBitmap, int width, int height, string directory, string filename, string extension)
{var physicalPath = directory + filename + extension;using (var newImage = new Bitmap(width, height)){using (var graphic = GetGraphic(originBitmap, newImage)){graphic.DrawImage(originBitmap, 0, 0, width, height);using (var encoderParameters = new EncoderParameters(1)){encoderParameters.Param[0] = new EncoderParameter(Encoder.Quality, 100L);newImage.Save(physicalPath,ImageCodecInfo.GetImageEncoders().Where(x => x.FilenameExtension.Contains(extension.ToUpperInvariant())).FirstOrDefault(),encoderParameters);}}}
}private Graphics GetGraphic(Image originImage, Bitmap newImage)
{newImage.SetResolution(originImage.HorizontalResolution, originImage.VerticalResolution);var graphic = Graphics.FromImage(newImage);graphic.InterpolationMode = System.Drawing.Drawing2D.InterpolationMode.HighQualityBicubic;graphic.SmoothingMode = System.Drawing.Drawing2D.SmoothingMode.HighQuality;graphic.PixelOffsetMode = System.Drawing.Drawing2D.PixelOffsetMode.HighQuality;graphic.CompositingQuality = System.Drawing.Drawing2D.CompositingQuality.HighQuality;return graphic;
}