解决GDI+的图像质量的问题

最近在完成一个文章发布系统时需要给图片添加水印，采用GDI+的DrawString后发现图像质量非常糟糕，后来从其他地方找到如下代码，经过试验 图像质量大幅提高：

// 上传成功，加水印    
                        
                         string  path = UploadFileDestination  +  UploadFileName;
                        System.Drawing.Image img  =  System.Drawing.Image.FromFile(path);
            System.Drawing.Imaging.ImageFormat thisFormat  =  img.RawFormat;

             // Size newSize = NewSize(maxWidth, maxHeight, img.Width, img.Height);
             // Bitmap outBmp = new Bitmap(newSize.Width, newSize.Height);
            Graphics g  =  Graphics.FromImage(img);

             //  设置画布的描绘质量
            g.CompositingQuality  =  CompositingQuality.HighQuality; 
            g.SmoothingMode  =  SmoothingMode.HighQuality; 
            g.InterpolationMode  =  InterpolationMode.HighQualityBicubic;

            g.DrawImage(img,  0 ,  0 , img.Width, img.Height);
                
            Font f  =   new  Font( " Arial " , 9 );
                Brush b  =   new  SolidBrush(Color.Black);
                Brush c  =   new  SolidBrush(Color.White);
                 string  addText  =   " .com在线 " ;
                
                g.DrawString(addText, f, b,  3 ,  3 );
                g.DrawString(addText, f, c,  2 ,  2 );
                
                g.DrawString(addText, f, b, img.Width - 140 , img.Height - 15 );
                g.DrawString(addText, f, c, img.Width - 141 , img.Height - 16 );
                g.Dispose();        
            

             //  以下代码为保存图片时，设置压缩质量
            EncoderParameters encoderParams  =   new  EncoderParameters();
             long [] quality  =   new   long [ 1 ];
            quality[ 0 ]  =   100 ;

            EncoderParameter encoderParam  =   new  EncoderParameter(System.Drawing.Imaging.Encoder.Quality, quality);
            encoderParams.Param[ 0 ]  =  encoderParam;

             // 获得包含有关内置图像编码解码器的信息的ImageCodecInfo 对象。
            ImageCodecInfo[] arrayICI  =  ImageCodecInfo.GetImageEncoders();
            ImageCodecInfo jpegICI  =   null ;
             for  ( int  x  =   0 ; x  <  arrayICI.Length; x ++ )
             {
                if (arrayICI[x].FormatDescription.Equals("JPEG"))
                {
                    jpegICI = arrayICI[x];//设置JPEG编码
                    break;
                }
            }

             string  newPath  =  (UploadFileDestination + RNDFile()) + newext;

             if  (jpegICI  !=   null )
             {
                img.Save(newPath, jpegICI, encoderParams);
            }
             else
             {
                img.Save(newPath, thisFormat);
            }
            
            img.Dispose();
            
                        

                 // 保存加水印过后的图片,删除原始图片
                

                 if (File.Exists(path))
                 {
                    File.Delete(path);
                }                             
                    
                        
                     // 水印添加完成