C#生成高清缩略图

首先是前台代码：

1 <div>
2     <asp:FileUpload ID="photoFile" runat="server" />
3     <asp:Button ID="Button1" runat="server" Text="Button" OnClick="Button1_Click" />
4     <asp:Label ID="Label1" runat="server" Text="Label"></asp:Label>
5 </div>

然后是后台代码：

 1 using System;
 2 using System.Drawing;
 3 using System.IO;
 4 using System.Web;
 5 
 6 namespace Shop
 7 {
 8     public partial class Test : System.Web.UI.Page
 9     {
10         protected void Page_Load(object sender, EventArgs e)
11         {
12         }
13 
14         /// <summary>
15         /// 压缩
16         /// </summary>
17         /// <param name="sender"></param>
18         /// <param name="e"></param>
19         protected void Button1_Click(object sender, EventArgs e)
20         {
21             HttpPostedFile file = photoFile.PostedFile;
22             if (!file.ContentType.Contains("image"))
23             {
24                 this.Label1.Text = "照片格式不合法";
25             }
26             string ext = Path.GetExtension(file.FileName).ToLower();
27             if (ext != ".jpg" && ext != ".gif" && ext != ".png" && ext != ".jpeg")
28             {
29                 this.Label1.Text = "请您上传jpg、gif、png图片";
30             }
31             if (file.ContentLength > 5 * 1024 * 1024)
32             {
33                 this.Label1.Text = "请您上传512字节内的图片";
34             }
35             string newName = Guid.NewGuid().ToString();
36 
37             string tempPath = "upload/";
38 
39             string img = tempPath + newName + ext;
40 
41             string filePath = Server.MapPath(img);
42 
43             try
44             {
45                 using (System.Drawing.Image originalImage = System.Drawing.Image.FromStream(file.InputStream))
46                 {
47                     GetThumbnail(originalImage, 280, 160).Save(filePath);
48                 }
49                 this.Label1.Text = "压缩成功！";
50             }
51             catch (Exception ex)
52             {
53                 
54                 throw ex;
55             }
56         }
57 
58         //---------------------------------------------为图片生成缩略图-----------------------
59         /// <summary> 
60         /// 为图片生成缩略图   
61         /// </summary> 
62         /// <param name="phyPath">原图片的路径</param> 
63         /// <param name="width">缩略图宽</param> 
64         /// <param name="height">缩略图高</param> 
65         /// <returns></returns> 
66         public System.Drawing.Image GetThumbnail(System.Drawing.Image image, int width, int height)
67         {
68             Bitmap bmp = new Bitmap(width, height);
69             //从Bitmap创建一个System.Drawing.Graphics 
70             System.Drawing.Graphics gr = System.Drawing.Graphics.FromImage(bmp);
71             //设置  
72             gr.SmoothingMode = System.Drawing.Drawing2D.SmoothingMode.HighQuality;
73             //下面这个也设成高质量 
74             gr.CompositingQuality = System.Drawing.Drawing2D.CompositingQuality.HighQuality;
75             //下面这个设成High 
76             gr.InterpolationMode = System.Drawing.Drawing2D.InterpolationMode.HighQualityBicubic;
77             //把原始图像绘制成上面所设置宽高的缩小图 
78             System.Drawing.Rectangle rectDestination = new System.Drawing.Rectangle(0, 0, width, height);
79 
80             gr.DrawImage(image, rectDestination, 0, 0, image.Width, image.Height,GraphicsUnit.Pixel);
81 
82             return bmp;
83         }
84         //----------------------------------------------------------------------------------------
85     }
86 }

运行效果：

最终上传（文件夹要已经存在）：

以上就是缩略图的制作。