生成缩略图的一个方法

    private static void MakeThumbnail(string originalImagePath, string thumbnailPath, int width, int height, string mode)
        {
            System.Drawing.Image originalImage = System.Drawing.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":               
                    break;
                case "W":                    
                    toheight = originalImage.Height * width/originalImage.Width;
                    break;
                case "H":
                    towidth = originalImage.Width * height/originalImage.Height;                    
                    break;        
                case "Cut":                
                    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;
            }    
            System.Drawing.Image bitmap = new System.Drawing.Bitmap(towidth,toheight);
            Graphics g = System.Drawing.Graphics.FromImage(bitmap);
            g.InterpolationMode = System.Drawing.Drawing2D.InterpolationMode.High;
            g.SmoothingMode = System.Drawing.Drawing2D.SmoothingMode.HighQuality;
            g.Clear(Color.Transparent);        
            g.DrawImage(originalImage, new Rectangle(0, 0, towidth, toheight), 
                new Rectangle(x, y, ow,oh),
                GraphicsUnit.Pixel);
            try
            {            
                bitmap.Save(thumbnailPath, System.Drawing.Imaging.ImageFormat.Jpeg);
            }
            catch(System.Exception e)
            {
                throw e;
            }
            finally
            {
                originalImage.Dispose();
                bitmap.Dispose();                        
                g.Dispose();
            }
        }

需引用命名空间 System.Drawing;