C#生成高清縮略圖

    /// <summary>

       /// 為圖片生成縮略圖

       /// </summary>

       /// <param name="phyPath">原圖片的路徑</param>

       /// <param name="width">縮略圖寬</param>

       /// <param name="height">縮略圖高</param>

       /// <returns></returns>

       public System.Drawing.Image GetThumbnail(System.Drawing.Image image, int width, int height)

       {

           Bitmap bmp = new Bitmap(width, height);

           //從Bitmap創建一個System.Drawing.Graphics

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

           //設置

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

           //下面這個也設成高質量

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

           //下面這個設成High

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

           //把原始圖像繪制成上面所設置寬高的縮小圖

           System.Drawing.Rectangle rectDestination = new System.Drawing.Rectangle(0, 0, width, height);


       gr.DrawImage(image, rectDestination, 0, 0, image.Width, image.Height, GraphicsUnit.Pixel);  
       return bmp;  
   }  </pre><br />

調用方法
    HttpPostedFile file = photoFile.PostedFile;  
            if (!file.ContentType.Contains("image"))  
            {  
    return "照片格式不合法";  
            }  
            string ext = Path.GetExtension(file.FileName).ToLower();  
            if (ext != ".jpg" && ext != ".gif" && ext != ".png" && ext != ".jpeg")  
            {  
    return "請您上傳jpg、gif、png圖片";  
            }  
            if (file.ContentLength > 5 * 1024 * 1024)  
            {  
    return "請您上傳512字節內的圖片";  
            }  
            string newName = Guid.NewGuid().ToString();  
            string tempPath = "upload/";  
            string img = tempPath + newName + ext;  
            string filePath = Server.MapPath(img);  
            if (!Directory.Exists(tempPath))  
            {  
                Directory.CreateDirectory(tempPath);  
            }  
            using (System.Drawing.Image originalImage = System.Drawing.Image.FromStream(file.InputStream))  
            {  
                GetThumbnail(originalImage, 504, 374).Save(filePath);  
            }