C#生成缩略图

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1. /// 生成缩略图   
2.     /// </summary>   
3.     /// <param name="originalImagePath">源图路径</param>   
4.     /// <param name="thumbnailPath">缩略图路径</param>   
5.     /// <param name="width">缩略图宽度</param>   
6.     /// <param name="height">缩略图高度</param>   
7.     /// <param name="mode">生成缩略图的方式:HW指定高宽缩放(可能变形);W指定宽，高按比例 H指定高，宽按比例 Cut指定高宽裁减(不变形)</param>　　   
8.     /// <param name="mode">要缩略图保存的格式(gif,jpg,bmp,png) 为空或未知类型都视为jpg</param>　　   
9.     public static void MakeThumbnail(string originalImagePath, string thumbnailPath, int width, int height, string mode, string imageType)  
10.     {  
11.         Image originalImage = Image.FromFile(originalImagePath);  
12.         int towidth = width;  
13.         int toheight = height;  
14.         int x = 0;  
15.         int y = 0;  
16.         int ow = originalImage.Width;  
17.         int oh = originalImage.Height;  
18.         switch (mode)  
19.         {  
20.             case "HW"://指定高宽缩放（可能变形）　　　　　　　　   
21.                 break;  
22.             case "W"://指定宽，高按比例　　　　　　　　　　   
23.                 toheight = originalImage.Height * width / originalImage.Width;  
24.                 break;  
25.             case "H"://指定高，宽按比例   
26.                 towidth = originalImage.Width * height / originalImage.Height;  
27.                 break;  
28.             case "Cut"://指定高宽裁减（不变形）　　　　　　　　   
29.                 if ((double)originalImage.Width / (double)originalImage.Height > (double)towidth / (double)toheight)  
30.                 {  
31.                     oh = originalImage.Height;  
32.                     ow = originalImage.Height * towidth / toheight;  
33.                     y = 0;  
34.                     x = (originalImage.Width - ow) / 2;  
35.                 }  
36.                 else  
37.                 {  
38.                     ow = originalImage.Width;  
39.                     oh = originalImage.Width * height / towidth;  
40.                     x = 0;  
41.                     y = (originalImage.Height - oh) / 2;  
42.                 }  
43.                 break;  
44.             default:  
45.                 break;  
46.         }  
47.         //新建一个bmp图片   
48.         Image bitmap = new System.Drawing.Bitmap(towidth, toheight);  
49.         //新建一个画板   
50.         Graphics g = System.Drawing.Graphics.FromImage(bitmap);  
51.         //设置高质量插值法   
52.         g.InterpolationMode = System.Drawing.Drawing2D.InterpolationMode.High;  
53.         //设置高质量,低速度呈现平滑程度   
54.         g.SmoothingMode = System.Drawing.Drawing2D.SmoothingMode.HighQuality;  
55.         //清空画布并以透明背景色填充   
56.         g.Clear(Color.Transparent);  
57.         //在指定位置并且按指定大小绘制原图片的指定部分   
58.         g.DrawImage(originalImage, new Rectangle(0, 0, towidth, toheight),  
59.            new Rectangle(x, y, ow, oh),  
60.            GraphicsUnit.Pixel);  
61.         try  
62.         {  
63.             //以jpg格式保存缩略图   
64.             switch (imageType.ToLower())  
65.             {  
66.                 case "gif":  
67.                     bitmap.Save(thumbnailPath, System.Drawing.Imaging.ImageFormat.Gif);  
68.                     break;  
69.                 case "jpg":  
70.                     bitmap.Save(thumbnailPath, System.Drawing.Imaging.ImageFormat.Jpeg);  
71.                     break;  
72.                 case "bmp":  
73.                     bitmap.Save(thumbnailPath, System.Drawing.Imaging.ImageFormat.Bmp);  
74.                     break;  
75.                 case "png":  
76.                     bitmap.Save(thumbnailPath, System.Drawing.Imaging.ImageFormat.Png);  
77.                     break;  
78.                 default:  
79.                     bitmap.Save(thumbnailPath, System.Drawing.Imaging.ImageFormat.Jpeg);  
80.                     break;  
81.             }  
82.         }  
83.         catch (System.Exception e)  
84.         {  
85.             throw e;  
86.         }  
87.         finally  
88.         {  
89.             originalImage.Dispose();  
90.             bitmap.Dispose();  
91.             g.Dispose();  
92.         }  
93.     }  

==================================

C#生成缩略图 (通用模式) 


用数据库保存图片的路径和文件名称，把文件保存在文件夹中.
//保存在数据库中的文件路径
ArrayList arrFilePath=new ArrayList();
arrFilePath=myCommonMethod.UploadPic(Files,"/UpLoads/UpPicture/");
//获取文件名称
string fileName=arrFilePath[0].SubString(arrFilePath[0].LastIndexOf("/")+1);
//源图路径（物理路径）
originalImagePath=Request.PhysicalApplicationPath+"/UpLoads/UpPicture/"+fileName;
//缩略图路径（物理路径）
thumbnailPath     =Request.PhysicalApplicationPath+"/UpLoads/UpPicture/"+"thumb_"+fileName;
//调用生成缩略图方法
this.MakeThumbnail(originalImagePath,thumbnailPath,120,150, strMode out outthumbnailPath);

#region  生成缩略图 
  ///<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  void MakeThumbnail(string originalImagePath,  string thumbnailPath, int width, int height, string mode out string outthumbnailPath) 
  { 
   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"://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 
   System.Drawing.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); 
    outthumbnailPath=thumbnailPath;
   } 
   catch(System.Exception e) 
   { 
    throw e; 
   } 
   finally 
   { 
    originalImage.Dispose(); 
    bitmap.Dispose();                         
    g.Dispose(); 
   } 
  } 

C#生成缩略图

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原文地址：http://www.cnblogs.com/qq260250932/p/5293883.html