C#生成图片缩略图(2种思路)

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

  1 using System.IO;
  2 using System.Drawing;
  3 using System.Drawing.Imaging;
  4 
  5 /// <summary>
  6 /// 图片处理类
  7 /// 1、生成缩略图片或按照比例改变图片的大小和画质
  8 /// 2、将生成的缩略图放到指定的目录下
  9 /// </summary>
 10 public class ImageClass
 11 {
 12     public Image ResourceImage;
 13     private int ImageWidth;
 14     private int ImageHeight;
 15 
 16     public string ErrMessage;
 17 
 18     /// <summary>
 19     /// 类的构造函数
 20     /// </summary>
 21     /// <param name="ImageFileName">图片文件的全路径名称</param>
 22     public ImageClass(string ImageFileName)
 23     {
 24         ResourceImage=Image.FromFile(ImageFileName);
 25      ErrMessage="";
 26     }
 27 
 28     public bool ThumbnailCallback()
 29     {
 30      return false;
 31     }
 32 
 33     /// <summary>
 34     /// 生成缩略图重载方法1，返回缩略图的Image对象
 35     /// </summary>
 36     /// <param name="Width">缩略图的宽度</param>
 37     /// <param name="Height">缩略图的高度</param>
 38     /// <returns>缩略图的Image对象</returns>
 39     public Image GetReducedImage(int Width,int Height)
 40     {
 41      try
 42      {
 43       Image ReducedImage;
 44 
 45       Image.GetThumbnailImageAbort callb=new Image.GetThumbnailImageAbort(ThumbnailCallback); 
 46      
 47       ReducedImage=ResourceImage.GetThumbnailImage(Width,Height,callb,IntPtr.Zero);
 48   
 49       return ReducedImage;
 50      }
 51      catch(Exception e)
 52      {
 53       ErrMessage=e.Message; 
 54          return null;
 55      }
 56     }
 57 
 58     /// <summary>
 59     /// 生成缩略图重载方法2，将缩略图文件保存到指定的路径
 60     /// </summary>
 61     /// <param name="Width">缩略图的宽度</param>
 62     /// <param name="Height">缩略图的高度</param>
 63     /// <param name="targetFilePath">缩略图保存的全文件名，(带路径)，参数格式：D:\Images\filename.jpg</param>
 64     /// <returns>成功返回true，否则返回false</returns>
 65     public bool GetReducedImage(int Width,int Height,string targetFilePath)
 66     {
 67      try
 68      {
 69       Image ReducedImage;
 70 
 71       Image.GetThumbnailImageAbort callb=new Image.GetThumbnailImageAbort(ThumbnailCallback); 
 72      
 73       ReducedImage=ResourceImage.GetThumbnailImage(Width,Height,callb,IntPtr.Zero);
 74       ReducedImage.Save(@targetFilePath,ImageFormat.Jpeg);
 75 
 76       ReducedImage.Dispose(); 
 77   
 78       return true;
 79      }
 80      catch(Exception e)
 81      {
 82       ErrMessage=e.Message; 
 83       return false;
 84      }
 85     }
 86 
 87     /// <summary>
 88     /// 生成缩略图重载方法3，返回缩略图的Image对象
 89     /// </summary>
 90     /// <param name="Percent">缩略图的宽度百分比 如：需要百分之80，就填0.8</param>  
 91     /// <returns>缩略图的Image对象</returns>
 92     public Image GetReducedImage(double Percent)
 93     {
 94      try
 95      {
 96       Image ReducedImage;
 97 
 98       Image.GetThumbnailImageAbort callb=new Image.GetThumbnailImageAbort(ThumbnailCallback);
 99 
100       ImageWidth=Convert.ToInt32(ResourceImage.Width*Percent);
101       ImageHeight=Convert.ToInt32(ResourceImage.Width*Percent);
102      
103       ReducedImage=ResourceImage.GetThumbnailImage(ImageWidth,ImageHeight,callb,IntPtr.Zero);
104   
105       return ReducedImage;
106      }
107      catch(Exception e)
108      {
109       ErrMessage=e.Message; 
110       return null;
111      }
112     }
113 
114     /// <summary>
115     /// 生成缩略图重载方法4，返回缩略图的Image对象
116     /// </summary>
117     /// <param name="Percent">缩略图的宽度百分比 如：需要百分之80，就填0.8</param>  
118     /// <param name="targetFilePath">缩略图保存的全文件名，(带路径)，参数格式：D:\Images\filename.jpg</param>
119     /// <returns>成功返回true,否则返回false</returns>
120     public bool GetReducedImage(double Percent,string targetFilePath)
121     {
122      try
123      {
124       Image ReducedImage;
125 
126       Image.GetThumbnailImageAbort callb=new Image.GetThumbnailImageAbort(ThumbnailCallback);
127 
128       ImageWidth=Convert.ToInt32(ResourceImage.Width*Percent);
129       ImageHeight=Convert.ToInt32(ResourceImage.Width*Percent);
130      
131       ReducedImage=ResourceImage.GetThumbnailImage(ImageWidth,ImageHeight,callb,IntPtr.Zero);
132 
133       ReducedImage.Save(@targetFilePath,ImageFormat.Jpeg);
134 
135       ReducedImage.Dispose(); 
136   
137       return true;
138      }
139      catch(Exception e)
140      {
141       ErrMessage=e.Message; 
142       return false;
143      }
144     }
145 }