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Asp.Net 上传图片并生成高清晰缩略图

在asp.net中,上传图片功能或者是常用的,生成缩略图也是常用的。baidu或者google,c#的方法也是很多的,但是一用却发现缩略图不清晰啊,缩略图片太大之类的事情,下面是我在处理图片上的代码,效果不错,所以拿出来分享,(效果能达到一些绘图软件的效果)

代码如下:

  1 /// <summary>
  2     /// asp.net上传图片并生成缩略图
  3     /// </summary>
  4     /// <param name="upImage">HtmlInputFile控件</param>
  5     /// <param name="sSavePath">保存的路径,些为相对服务器路径的下的文件夹</param>
  6     /// <param name="sThumbExtension">缩略图的thumb</param>
  7     /// <param name="intThumbWidth">生成缩略图的宽度</param>
  8     /// <param name="intThumbHeight">生成缩略图的高度</param>
  9     /// <returns>缩略图名称</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 "没有选择上传图片";            
 20             //获取upImage选择文件的扩展名
 21             string extendName = System.IO.Path.GetExtension(myFile.FileName).ToLower();
 22             //判断是否为图片格式
 23             if (extendName != ".jpg" && extendName != ".jpge" && extendName != ".gif" && extendName != ".bmp" && extendName != ".png")
 24                 return "图片格式不正确";
 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             //检查当前文件夹下是否有同名图片,有则在文件名+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             //以上为上传原图
 43             try
 44             {
 45                 //原图加载
 46                 using (System.Drawing.Image sourceImage = System.Drawing.Image.FromFile(System.Web.HttpContext.Current.Server.MapPath(sSavePath + sFilename)))
 47                 {
 48                     //原图宽度和高度
 49                     int width = sourceImage.Width;
 50                     int height = sourceImage.Height;
 51                     int smallWidth;
 52                     int smallHeight;
 53                     //获取第一张绘制图的大小,(比较 原图的宽/缩略图的宽  和 原图的高/缩略图的高)
 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                     //判断缩略图在当前文件夹下是否同名称文件存在
 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                     //缩略图保存的绝对路径
 74                     string smallImagePath = System.Web.HttpContext.Current.Server.MapPath(sSavePath) + sThumbFile;
 75                     //新建一个图板,以最小等比例压缩大小绘制原图
 76                     using (System.Drawing.Image bitmap = new System.Drawing.Bitmap(smallWidth, smallHeight))
 77                     {
 78                         //绘制中间图
 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                         //新建一个图板,以缩略图大小绘制中间图
 93                         using (System.Drawing.Image bitmap1 = new System.Drawing.Bitmap(intThumbWidth, intThumbHeight))
 94                         {
 95                       //绘制缩略图  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                 //出错则删除
115                 System.IO.File.Delete(System.Web.HttpContext.Current.Server.MapPath(sSavePath + sFilename));
116                 return "图片格式不正确";
117             }
118             //返回缩略图名称
119             return sThumbFile;
120         }
121         return "没有选择图片";
122     }

HtmlInputFile控件我想大家都应该知道的,就是input type=file....

 

下面把调用代码也一起C上来

 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>图片上传-柯乐义</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     }

这样就会在你的UpLoad文件夹下多出两张图片,一张是原图,一张是缩略图。

 

 

提供一个更好的算法,由于没有时间去测试和调试,仅供参考

即,在第一步等比例缩小的时候,可以分多次,即把原图到上面代码的中间图以百分比缩小,

例如:原图为500*500 我要缩略成100*80,上面代码程序会先绘制一张100*100的中间图,再在这图片上绘制100*80的,

在绘制100*100中间图之前如果先绘300*300的中间图,再在300*300的基础上再绘100*100然后再绘100*80这样会比我上面的代码效果更好,图片更清晰,即中间图越多,效果越好,大家可以去试试。

开发技术文章:http://www.cnblogs.com/sosoft/p/kaifajishu.html

posted on 2014-01-16 01:18  柔城  阅读(11753)  评论(6编辑  收藏  举报

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