不经保存，直接生成上传图片的等比例的高质量缩略图



	 

	我们可以使用FileUpload.FileBytes属性直接得到上传文件的字节数组，从而可以直接生成上传文件的缩略图。代码如下：

	 

	ASPX 代码

	<%@ Page Language="C#" %>

	<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">

	<script runat="server">

	 

	  protected void Button1_Click(object sender, EventArgs e)

	  {

	    String fileExt = System.IO.Path.GetExtension(FileUpload1.FileName);

	    System.Drawing.Image image = System.Drawing.Image.FromStream(new System.IO.MemoryStream(FileUpload1.FileBytes));

	    int newWidth = 300, newHeight = 200;

	    if ((decimal)image.Width / image.Height > (decimal)newWidth / newHeight)

	    {

	      newHeight =Convert.ToInt32((decimal)image.Height * newWidth / image.Width);

	    }

	    else if ((decimal)image.Width / image.Height < (decimal)newWidth / newHeight)

	    {

	      newWidth = Convert.ToInt32((decimal)image.Width * newHeight / image.Height);     

	    }

	    System.Drawing.Bitmap bmp = new System.Drawing.Bitmap(newWidth, newHeight);

	    System.Drawing.Graphics g = System.Drawing.Graphics.FromImage(bmp);

	    g.SmoothingMode = System.Drawing.Drawing2D.SmoothingMode.HighQuality;

	    g.CompositingQuality = System.Drawing.Drawing2D.CompositingQuality.HighQuality;

	    g.InterpolationMode = System.Drawing.Drawing2D.InterpolationMode.High;

	    System.Drawing.Rectangle rectDestination = new System.Drawing.Rectangle(0, 0, newWidth, newHeight);

	    g.DrawImage(image, rectDestination, 0, 0, image.Width, image.Height, System.Drawing.GraphicsUnit.Pixel);

	    bmp.Save(Server.MapPath("~/") + DateTime.Now.ToString("yyyyMMddHHmmss") + fileExt);

	    bmp.Dispose();

	    image.Dispose();

	  }

	</script>

	<html xmlns="http://www.w3.org/1999/xhtml">

	<head runat="server">

	  <title>不经保存，直接生成上传图片的等比例的高质量缩略图</title>

	</head>

	<body>

	  <form id="form1" runat="server">

	  <asp:FileUpload ID="FileUpload1" runat="server" />

	  <asp:Button ID="Button1" runat="server" onclick="Button1_Click" Text="上传并生成缩略图" />

	  </form>

	</body>

	</html>

补充：Web开发 , ASP.Net ,