/// <summary>

        /// 创建缩略图

        /// </summary>

        /// <param name="srcFileName"></param>

        /// <param name="destFileName"></param>

        private static void CreateThumbnailImage(string srcFileName, string destFileName)

        {

            using (var img = new Bitmap(srcFileName))

            {

                Size originalSize = new Size(img.Width, img.Height);

                Size targetSize = new Size(, );

                targetSize = CalculateNewImageSize(originalSize, targetSize);

                using (

                    var bitmap = new Bitmap(targetSize.Width, targetSize.Height, PixelFormat.Format32bppArgb))

                {

                    using (Graphics g = Graphics.FromImage(bitmap))

                    {

                        g.InterpolationMode = InterpolationMode.Low;

                        using (var wrapmode = new ImageAttributes())

                        {

                            wrapmode.SetWrapMode(WrapMode.TileFlipXY);

                            g.DrawImage(img, new Rectangle(, , targetSize.Width, targetSize.Height),

                                , ,

                                img.Width,

                                img.Height,

                                GraphicsUnit.Pixel,

                                wrapmode);

                        }

                    }

                    bitmap.Save(destFileName);

                }

            }

        }

        /// <summary>

        /// 计算缩略图的尺寸

        /// </summary>

        /// <param name="originalSize"></param>

        /// <param name="targetSize"></param>

        /// <returns></returns>

        private static Size CalculateNewImageSize(Size originalSize, Size targetSize)

        {

            if (originalSize.Width <= targetSize.Width&&

                originalSize.Height<=targetSize.Height)

            {

                //目标尺寸比原尺寸大，那么直接使用原尺寸

                return originalSize;

            }

            double targetRatio = GetRatio(targetSize);

            double originalRatio = GetRatio(originalSize);

            var size = new Size(targetSize.Width, targetSize.Height);

            if (originalRatio < targetRatio)

            {

                size.Width = (originalSize.Width*targetSize.Height)/originalSize.Height;

            }

            else

            {

                size.Height = (originalSize.Height*targetSize.Width)/originalSize.Width;

            }

            return size;

        }

        private static double GetRatio(Size size)

        {

            return (double) size.Width/size.Height;

        }