Asp.Net 上傳圖片並生成高清晰縮略圖

在asp.net中,上傳圖片功能或者是經常使用的,生成縮略圖也是經常使用的。baidu或者google,c#的方法也是不少的,可是一用卻發現縮略圖不清晰啊,縮略圖片太大之類的事情,下面是我在處理圖片上的代碼,效果不錯,因此拿出來分享,(效果能達到一些繪圖軟件的效果)html

代碼以下:算法

  1 /// <summary>
  2     /// asp.net上傳圖片並生成縮略圖
  3     /// </summary>
  4     /// <param name="upImage">HtmlInputFile控件</param>
  5     /// <param name="sSavePath">保存的路徑,些爲相對服務器路徑的下的文件夾</param>
  6     /// <param name="sThumbExtension">縮略圖的thumb</param>
  7     /// <param name="intThumbWidth">生成縮略圖的寬度</param>
  8     /// <param name="intThumbHeight">生成縮略圖的高度</param>
  9     /// <returns>縮略圖名稱</returns>
 10     public string UpLoadImage(HtmlInputFile upImage, string sSavePath, string sThumbExtension, int intThumbWidth, int intThumbHeight)
 11     {
 12         string sThumbFile = "";
 13         string sFilename = "";        
 14         if (upImage.PostedFile != null)
 15         {
 16             HttpPostedFile myFile = upImage.PostedFile;
 17             int nFileLen = myFile.ContentLength;
 18             if (nFileLen == 0)
 19                 return "沒有選擇上傳圖片";            
 20             //獲取upImage選擇文件的擴展名
 21             string extendName = System.IO.Path.GetExtension(myFile.FileName).ToLower();
 22             //判斷是否爲圖片格式
 23             if (extendName != ".jpg" && extendName != ".jpge" && extendName != ".gif" && extendName != ".bmp" && extendName != ".png")
 24                 return "圖片格式不正確";
 25             
 26             byte[] myData = new Byte[nFileLen];
 27             myFile.InputStream.Read(myData, 0, nFileLen);
 28             sFilename = System.IO.Path.GetFileName(myFile.FileName);
 29             int file_append = 0;
 30             //檢查當前文件夾下是否有同名圖片,有則在文件名+1
 31             while (System.IO.File.Exists(System.Web.HttpContext.Current.Server.MapPath(sSavePath + sFilename)))
 32             {
 33                 file_append++;
 34                 sFilename = System.IO.Path.GetFileNameWithoutExtension(myFile.FileName)
 35                     + file_append.ToString() + extendName;
 36             }
 37             System.IO.FileStream newFile
 38                 = new System.IO.FileStream(System.Web.HttpContext.Current.Server.MapPath(sSavePath + sFilename),
 39                 System.IO.FileMode.Create, System.IO.FileAccess.Write);
 40             newFile.Write(myData, 0, myData.Length);
 41             newFile.Close();
 42             //以上爲上傳原圖
 43             try
 44             {
 45                 //原圖加載
 46                 using (System.Drawing.Image sourceImage = System.Drawing.Image.FromFile(System.Web.HttpContext.Current.Server.MapPath(sSavePath + sFilename)))
 47                 {
 48                     //原圖寬度和高度
 49                     int width = sourceImage.Width;
 50                     int height = sourceImage.Height;
 51                     int smallWidth;
 52                     int smallHeight;
 53                     //獲取第一張繪製圖的大小,(比較 原圖的寬/縮略圖的寬  和 原圖的高/縮略圖的高)
 54                     if (((decimal)width) / height <= ((decimal)intThumbWidth) / intThumbHeight)
 55                     {
 56                         smallWidth = intThumbWidth;
 57                         smallHeight = intThumbWidth * height / width;
 58                     }
 59                     else
 60                     {
 61                         smallWidth = intThumbHeight * width / height;
 62                         smallHeight = intThumbHeight;
 63                     }
 64                     //判斷縮略圖在當前文件夾下是否同名稱文件存在
 65                     file_append = 0;
 66                     sThumbFile = sThumbExtension + System.IO.Path.GetFileNameWithoutExtension(myFile.FileName) + extendName;
 67                     while (System.IO.File.Exists(System.Web.HttpContext.Current.Server.MapPath(sSavePath + sThumbFile)))
 68                     {
 69                         file_append++;
 70                         sThumbFile = sThumbExtension + System.IO.Path.GetFileNameWithoutExtension(myFile.FileName) +
 71                             file_append.ToString() + extendName;
 72                     }
 73                     //縮略圖保存的絕對路徑
 74                     string smallImagePath = System.Web.HttpContext.Current.Server.MapPath(sSavePath) + sThumbFile;
 75                     //新建一個圖板,以最小等比例壓縮大小繪製原圖
 76                     using (System.Drawing.Image bitmap = new System.Drawing.Bitmap(smallWidth, smallHeight))
 77                     {
 78                         //繪製中間圖
 79                         using (System.Drawing.Graphics g = System.Drawing.Graphics.FromImage(bitmap))
 80                         {
 81                             //高清,平滑
 82                             g.InterpolationMode = System.Drawing.Drawing2D.InterpolationMode.High;
 83                             g.SmoothingMode = System.Drawing.Drawing2D.SmoothingMode.HighQuality;
 84                             g.Clear(Color.Black);
 85                             g.DrawImage(
 86                             sourceImage,
 87                             new System.Drawing.Rectangle(0, 0, smallWidth, smallHeight),
 88                             new System.Drawing.Rectangle(0, 0, width, height),
 89                             System.Drawing.GraphicsUnit.Pixel
 90                             );
 91                         }
 92                         //新建一個圖板,以縮略圖大小繪製中間圖
 93                         using (System.Drawing.Image bitmap1 = new System.Drawing.Bitmap(intThumbWidth, intThumbHeight))
 94                         {
 95                       //繪製縮略圖  http://www.cnblogs.com/sosoft/
 96                             using (System.Drawing.Graphics g = System.Drawing.Graphics.FromImage(bitmap1))
 97                             {
 98                                 //高清,平滑
 99                                 g.InterpolationMode = System.Drawing.Drawing2D.InterpolationMode.High;
100                                 g.SmoothingMode = System.Drawing.Drawing2D.SmoothingMode.HighQuality;
101                                 g.Clear(Color.Black);
102                                 int lwidth = (smallWidth - intThumbWidth) / 2;
103                                 int bheight = (smallHeight - intThumbHeight) / 2;
104                                 g.DrawImage(bitmap, new Rectangle(0, 0, intThumbWidth, intThumbHeight), lwidth, bheight, intThumbWidth, intThumbHeight, GraphicsUnit.Pixel);
105                                 g.Dispose();
106                                 bitmap1.Save(smallImagePath, System.Drawing.Imaging.ImageFormat.Jpeg);
107                             }
108                         }
109                     }
110                 }
111             }
112             catch
113             {
114                 //出錯則刪除
115                 System.IO.File.Delete(System.Web.HttpContext.Current.Server.MapPath(sSavePath + sFilename));
116                 return "圖片格式不正確";
117             }
118             //返回縮略圖名稱
119             return sThumbFile;
120         }
121         return "沒有選擇圖片";
122     }

HtmlInputFile控件我想你們都應該知道的,就是input type=file....c#

 

下面把調用代碼也一塊兒C上來服務器

 1 <%@ Page Language="C#" AutoEventWireup="true" CodeFile="Default2.aspx.cs" Inherits="Default2" %>
 2 <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
 3 <html xmlns="http://www.w3.org/1999/xhtml" >
 4 <head runat="server">
 5     <title>圖片上傳-柯樂義</title>
 6 </head>
 7 <body>
 8     <form id="form1" runat="server">
 9     <div>        
10         <input id="File1" runat="server" type="file" /></div><asp:Button ID="Button1" runat="server" OnClick="Button1_Click" Text="Button" />
11     </form>
12 </body>
13 </html>

 

1 protected void Button1_Click(object sender, EventArgs e)
2     {
3         string a = this.UpLoadImage(this.File1, "UpLoad/", "thumb_", 118, 118);  
4     }

這樣就會在你的UpLoad文件夾下多出兩張圖片,一張是原圖,一張是縮略圖。app

 

 

提供一個更好的算法,因爲沒有時間去測試和調試,僅供參考asp.net

即,在第一步等比例縮小的時候,能夠分屢次,即把原圖到上面代碼的中間圖以百分比縮小,測試

例如:原圖爲500*500 我要縮略成100*80,上面代碼程序會先繪製一張100*100的中間圖,再在這圖片上繪製100*80的,this

在繪製100*100中間圖以前若是先繪300*300的中間圖,再在300*300的基礎上再繪100*100而後再繪100*80這樣會比我上面的代碼效果更好,圖片更清晰,即中間圖越多,效果越好,你們能夠去試試。google

開發技術文章:http://www.cnblogs.com/sosoft/p/kaifajishu.htmlspa

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