图片通过程序压缩和自动加水印处理清晰度下降

Question

图片通过程序压缩大小清晰度下降，颜色变浅了点
然后自动加水印处理，清晰度也下降了，压缩代码如下。高手指点压缩代码如下
/// <summary>
        /// 根据原图生成缩略图
        /// </summary>
        /// <param name="originalImagePath">原图象地址</param>
        /// <param name="thumbnailPath">生成的图像地址</param>
        /// <param name="width">生成图像的长度</param>
        /// <param name="height">生成图像的宽度</param>
        /// <param name="mode">模式</param>
        public static void MakeSmallPic(string originalImagePath, string thumbnailPath, int width, int height, string mode)
        {
            System.Drawing.Image originalImage;
            try
            {
                originalImage = System.Drawing.Image.FromFile(originalImagePath);
            }
            catch
            {
               //File.Delete(originalImagePath);
                return;
            }
            int towidth = width;
            int toheight = height;
            int x = 0;
            int y = 0;
            int ow = originalImage.Width;
            int oh = originalImage.Height;
            switch (mode)
            {
                case "HW"://指定高宽缩放（可能变形） 
                    break;
                case "MHW"://指定最大高宽缩放不变行 
                    if (originalImage.Width <= width && originalImage.Height <= height)
                    {
                        towidth = originalImage.Width;
                        toheight = originalImage.Height;
                    }
                    else
                    {
                        if (originalImage.Width > width)
                        {
                            towidth = width;
                            toheight = originalImage.Height * towidth / originalImage.Width;
                        }
                        if (toheight>height)
                        {
                           
                            towidth = towidth * height / toheight;
                            toheight = height;
                        }
                    
                    }
                    break;
                case "W": //指定宽，高按比例
                    toheight = originalImage.Height * width / originalImage.Width;
                    break;
                case "H": //指定高，宽按比例
                    towidth = originalImage.Width * height / originalImage.Height;
                    break;
                case "Cut": //指定高宽裁减（不变形）                
                    if ((originalImage.Width / originalImage.Height) > (towidth / toheight))
                    {
                        oh = originalImage.Height;
                        ow = originalImage.Height * towidth / toheight;
                        y = 0;
                        x = (originalImage.Width - ow) / 2;
                    }
                    else
                    {
                        ow = originalImage.Width;
                        oh = originalImage.Width * height / towidth;
                        x = 0;
                        y = (originalImage.Height - oh) / 2;
                    }
                    break;
                default:
                    break;            }
            // 新建一个bmp图片
            System.Drawing.Image bitmap;
            bitmap = new System.Drawing.Bitmap(towidth, toheight);
            //新建一个画板
            System.Drawing.Graphics g;
            g = System.Drawing.Graphics.FromImage(bitmap);
            //设置高质量插值法
            g.InterpolationMode = System.Drawing.Drawing2D.InterpolationMode.HighQualityBicubic;
            //设置高质量,低速度呈现平滑程度
            g.SmoothingMode = System.Drawing.Drawing2D.SmoothingMode.HighQuality;
            //清空画布并以透明背景色填充
            g.Clear(System.Drawing.Color.Transparent);
            //在指定位置并且按指定大小绘制原图片的指定部分
            g.DrawImage(originalImage, new System.Drawing.Rectangle(0, 0, towidth, toheight), new System.Drawing.Rectangle(x, y, ow, oh), System.Drawing.GraphicsUnit.Pixel);
            try
            {
                //以jpg格式保存缩略图
               // bitmap.Save(thumbnailPath, System.Drawing.Imaging.ImageFormat.Jpeg);
                //写数据库
                EncoderParameter p;
                EncoderParameters ps;
                ps = new EncoderParameters(1);
                p = new EncoderParameter(System.Drawing.Imaging.Encoder.Quality, 100L);
                ps.Param[0] = p;
                ImageCodecInfo ii = GetCodecInfo(getMimeType(originalImagePath));
                bitmap.Save(thumbnailPath, ii, ps);
            }
            catch (System.Exception e)
            {
                throw e;
            }
            finally
            {
                originalImage.Dispose();
                bitmap.Dispose();
                g.Dispose();
            }
        }
        private static ImageCodecInfo GetCodecInfo(string mimeType)
        {
            ImageCodecInfo[] CodecInfo = ImageCodecInfo.GetImageEncoders();
            foreach (ImageCodecInfo ici in CodecInfo)
            {
                if (ici.MimeType == mimeType) return ici;
            }
            return null;
        }
        public static string getMimeType(string filename)
        {
            string ext= filename.Substring(filename.LastIndexOf(".") + 1, (filename.Length - filename.LastIndexOf(".") - 1));
            string miniType = "image/jpeg";
            switch (ext)
            {
                case ".jpg":
                    miniType = "image/jpeg";
                    break;
                case ".gif":
                    miniType = "image/gif";
                    break;
                case ".png":
                    miniType = "image/png";
                    break;
            }
            return miniType;
        }加水印代码如下
       string imagePath = "原图地址";
                string waterMarkPath = "~/water.png"; //水印地址
                Image image = null;
                
                image = Image.FromFile(context.Server.MapPath(imagePath));
                Image waterMark = Image.FromFile(context.Server.MapPath(waterMarkPath));
                Graphics g = Graphics.FromImage(image);
                g.DrawImage(waterMark, image.Width/2 - waterMark.Width/2,
                    image.Height/2 - waterMark.Height/2, waterMark.Width, waterMark.Height);                waterMark.Dispose();
                g.Dispose();
               
                HttpResponse response = context.Response;
                response.Clear();
                //输出流的类型为图片
                response.ContentType = "image/jpeg";                 EncoderParameter p;
                 EncoderParameters ps;
                 ps = new EncoderParameters(1);
                 p = new EncoderParameter(Encoder.Quality, 100L);
                 ps.Param[0] = p;
                 ImageCodecInfo ii = GetCodecInfo(getMimeType(imagePath));
                image.Save(response.OutputStream,ii,ps);
                response.End();
                image.Dispose();

Answer 1

http://blog.csdn.net/fengyarongaa/article/details/6563148

Answer 2

高质量缩略图/// <summary>
        /// 生成缩略图
        /// </summary>
        /// <param name="originalImagePath">源图路径（物理路径）</param>
        /// <param name="thumbnailPath">缩略图路径（物理路径）</param>
        /// <param name="width">缩略图宽度</param>
        /// <param name="height">缩略图高度</param>
        /// <param name="mode">生成缩略图的方式</param>    
        public static void MakeThumbnail(string originalImagePath, string thumbnailPath, int width, int height, string mode)
        {
            Image originalImage = Image.FromFile(originalImagePath);
            
            int towidth = width;
            int toheight = height;
        
            int x = 0;
            int y = 0;
            int ow = originalImage.Width;
            int oh = originalImage.Height;                    switch (mode)
            {        
                case "HW"://指定高宽缩放（可能变形）                
                    break;
                case "W"://指定宽，高按比例                    
                    toheight = originalImage.Height * width/originalImage.Width;
                    break;
                case "H"://指定高，宽按比例
                    towidth = originalImage.Width * height/originalImage.Height;                    
                    break;        
                case "Cut"://指定高宽裁减（不变形）                
                    if((double)originalImage.Width/(double)originalImage.Height > (double)towidth/(double)toheight)
                    {
                        oh = originalImage.Height;
                        ow = originalImage.Height*towidth/toheight;
                        y = 0;
                        x = (originalImage.Width - ow)/2;
                    }
                    else
                    {
                        ow = originalImage.Width;
                        oh = originalImage.Width*height/towidth;
                        x = 0;
                        y = (originalImage.Height - oh)/2;
                    }
                    break;                    
                default :
                    break;
            }    
            
            //新建一个bmp图片
            Image bitmap = new System.Drawing.Bitmap(towidth,toheight);            //新建一个画板
            Graphics g = System.Drawing.Graphics.FromImage(bitmap);            //设置高质量插值法
            g.InterpolationMode = System.Drawing.Drawing2D.InterpolationMode.High;            //设置高质量,低速度呈现平滑程度
            g.SmoothingMode = System.Drawing.Drawing2D.SmoothingMode.HighQuality;            //清空画布并以透明背景色填充
            g.Clear(Color.Transparent);                    //在指定位置并且按指定大小绘制原图片的指定部分
            g.DrawImage(originalImage, new Rectangle(0, 0, towidth, toheight), 
                new Rectangle(x, y, ow,oh),
                GraphicsUnit.Pixel);            try
            {            
                //以jpg格式保存缩略图
                bitmap.Save(thumbnailPath, System.Drawing.Imaging.ImageFormat.Jpeg);
            }
            catch(System.Exception e)
            {
                throw e;
            }
            finally
            {
                originalImage.Dispose();
                bitmap.Dispose();                        
                g.Dispose();
            }
        }

Answer 3

高分求解决
除了使用NET内置的压缩外
有没有其他优秀的第三方组件
可以实现更好的效果