Asp.Net上传图片同时生成高清晰缩略图

时间:2022-09-25 21:11:19

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:

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/// <summary>
 /// asp.net上传图片并生成缩略图
 /// </summary>
 /// <param name="upImage">HtmlInputFile控件</param>
 /// <param name="sSavePath">保存的路径,些为相对服务器路径的下的文件夹</param>
 /// <param name="sThumbExtension">缩略图的thumb</param>
 /// <param name="intThumbWidth">生成缩略图的宽度</param>
 /// <param name="intThumbHeight">生成缩略图的高度</param>
 /// <returns>缩略图名称</returns>
 public string UpLoadImage(HtmlInputFile upImage, string sSavePath, string sThumbExtension, int intThumbWidth, int intThumbHeight)
 {
  string sThumbFile = "";
  string sFilename = ""
  if (upImage.PostedFile != null)
  {
   HttpPostedFile myFile = upImage.PostedFile;
   int nFileLen = myFile.ContentLength;
   if (nFileLen == 0)
    return "没有选择上传图片";  
   //获取upImage选择文件的扩展名
   string extendName = System.IO.Path.GetExtension(myFile.FileName).ToLower();
   //判断是否为图片格式
   if (extendName != ".jpg" && extendName != ".jpge" && extendName != ".gif" && extendName != ".bmp" && extendName != ".png")
    return "图片格式不正确";
   
   byte[] myData = new Byte[nFileLen];
   myFile.InputStream.Read(myData, 0, nFileLen);
   sFilename = System.IO.Path.GetFileName(myFile.FileName);
   int file_append = 0;
   //检查当前文件夹下是否有同名图片,有则在文件名+1
   while (System.IO.File.Exists(System.Web.HttpContext.Current.Server.MapPath(sSavePath + sFilename)))
   {
    file_append++;
    sFilename = System.IO.Path.GetFileNameWithoutExtension(myFile.FileName)
     + file_append.ToString() + extendName;
   }
   System.IO.FileStream newFile
    = new System.IO.FileStream(System.Web.HttpContext.Current.Server.MapPath(sSavePath + sFilename),
    System.IO.FileMode.Create, System.IO.FileAccess.Write);
   newFile.Write(myData, 0, myData.Length);
   newFile.Close();
   //以上为上传原图
   try
   {
    //原图加载
    using (System.Drawing.Image sourceImage = System.Drawing.Image.FromFile(System.Web.HttpContext.Current.Server.MapPath(sSavePath + sFilename)))
    {
     //原图宽度和高度
     int width = sourceImage.Width;
     int height = sourceImage.Height;
     int smallWidth;
     int smallHeight;
     //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)
     if (((decimal)width) / height <= ((decimal)intThumbWidth) / intThumbHeight)
     {
      smallWidth = intThumbWidth;
      smallHeight = intThumbWidth * height / width;
     }
     else
     {
      smallWidth = intThumbHeight * width / height;
      smallHeight = intThumbHeight;
     }
     //判断缩略图在当前文件夹下是否同名称文件存在
     file_append = 0;
     sThumbFile = sThumbExtension + System.IO.Path.GetFileNameWithoutExtension(myFile.FileName) + extendName;
     while (System.IO.File.Exists(System.Web.HttpContext.Current.Server.MapPath(sSavePath + sThumbFile)))
     {
      file_append++;
      sThumbFile = sThumbExtension + System.IO.Path.GetFileNameWithoutExtension(myFile.FileName) +
       file_append.ToString() + extendName;
     }
     //缩略图保存的绝对路径
     string smallImagePath = System.Web.HttpContext.Current.Server.MapPath(sSavePath) + sThumbFile;
     //新建一个图板,以最小等比例压缩大小绘制原图
     using (System.Drawing.Image bitmap = new System.Drawing.Bitmap(smallWidth, smallHeight))
     {
      //绘制中间图
      using (System.Drawing.Graphics g = System.Drawing.Graphics.FromImage(bitmap))
      {
       //高清,平滑
       g.InterpolationMode = System.Drawing.Drawing2D.InterpolationMode.High;
       g.SmoothingMode = System.Drawing.Drawing2D.SmoothingMode.HighQuality;
       g.Clear(Color.Black);
       g.DrawImage(
       sourceImage,
       new System.Drawing.Rectangle(0, 0, smallWidth, smallHeight),
       new System.Drawing.Rectangle(0, 0, width, height),
       System.Drawing.GraphicsUnit.Pixel
       );
      }
      //新建一个图板,以缩略图大小绘制中间图
      using (System.Drawing.Image bitmap1 = new System.Drawing.Bitmap(intThumbWidth, intThumbHeight))
      {
     //绘制缩略图 http://www.cnblogs.com/sosoft/
       using (System.Drawing.Graphics g = System.Drawing.Graphics.FromImage(bitmap1))
       {
        //高清,平滑
        g.InterpolationMode = System.Drawing.Drawing2D.InterpolationMode.High;
        g.SmoothingMode = System.Drawing.Drawing2D.SmoothingMode.HighQuality;
        g.Clear(Color.Black);
        int lwidth = (smallWidth - intThumbWidth) / 2;
        int bheight = (smallHeight - intThumbHeight) / 2;
        g.DrawImage(bitmap, new Rectangle(0, 0, intThumbWidth, intThumbHeight), lwidth, bheight, intThumbWidth, intThumbHeight, GraphicsUnit.Pixel);
        g.Dispose();
        bitmap1.Save(smallImagePath, System.Drawing.Imaging.ImageFormat.Jpeg);
       }
      }
     }
    }
   }
   catch
   {
    //出错则删除
    System.IO.File.Delete(System.Web.HttpContext.Current.Server.MapPath(sSavePath + sFilename));
    return "图片格式不正确";
   }
   //返回缩略图名称
   return sThumbFile;
  }
  return "没有选择图片";
 }

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

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<%@ Page Language="C#" AutoEventWireup="true" CodeFile="Default2.aspx.cs" Inherits="Default2" %>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml" >
<head runat="server">
 <title>图片上传-柯乐义</title>
</head>
<body>
 <form id="form1" runat="server">
 <div> 
  <input id="File1" runat="server" type="file" /></div><asp:Button ID="Button1" runat="server" OnClick="Button1_Click" Text="Button" />
 </form>
</body>
</html>

 

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

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。