public static void thumb(string rSrcImgPath, string rDstImgPath, int width, string lv = "h", int height = 0)

        {

            //利用Image对象装载源图像

            System.Drawing.Image image = System.Drawing.Image.FromFile(rSrcImgPath); 



            //创建一个System.Drawing.Bitmap对象，并设置你希望的缩略图的宽度和高度。

            int thumbWidth, thumbHeight;

            double srcWidth = image.Width;

            double srcHeight = image.Height;

            if (height == 0)//如果高度height为0,则原比例缩放

            {

                thumbWidth = width;

                double d = srcHeight / srcWidth;

                thumbHeight = Convert.ToInt32( d * width );

            }

            else//否则按要求宽高生成

            {

                thumbWidth = width;

                thumbHeight = height;

            }

            Bitmap bmp = new Bitmap(thumbWidth, thumbHeight); 



            //从Bitmap创建一个System.Drawing.Graphics对象，用来绘制高质量的缩小图。

            System.Drawing.Graphics gr = System.Drawing.Graphics.FromImage(bmp);



            if (lv=="h")

            {

                //设置 System.Drawing.Graphics对象的SmoothingMode属性为HighQuality

                gr.SmoothingMode = System.Drawing.Drawing2D.SmoothingMode.HighQuality;

                //下面这个也设成高质量

                gr.CompositingQuality = System.Drawing.Drawing2D.CompositingQuality.HighQuality;

                //下面这个设成High

                gr.InterpolationMode = System.Drawing.Drawing2D.InterpolationMode.High;

            }

            else if (lv=="m")

            {

                gr.SmoothingMode = System.Drawing.Drawing2D.SmoothingMode.None;



                gr.CompositingQuality = System.Drawing.Drawing2D.CompositingQuality.Default;



                gr.InterpolationMode = System.Drawing.Drawing2D.InterpolationMode.Default;



            }

            else if (lv=="l")

            {

                gr.SmoothingMode = System.Drawing.Drawing2D.SmoothingMode.None;



                gr.CompositingQuality = System.Drawing.Drawing2D.CompositingQuality.HighSpeed;



                gr.InterpolationMode = System.Drawing.Drawing2D.InterpolationMode.Low;

            }







            //把原始图像绘制成上面所设置宽高的缩小图

            System.Drawing.Rectangle rectDestination = new System.Drawing.Rectangle(0, 0, thumbWidth, thumbHeight);

            gr.DrawImage(image, rectDestination, 0, 0,Convert.ToInt32( srcWidth),Convert.ToInt32( srcHeight), GraphicsUnit.Pixel);



            //保存图像，大功告成！

            bmp.Save(rDstImgPath);



            //最后别忘了释放资源

            bmp.Dispose();

            image.Dispose();

        }