不经保存，直接生成上传图片的等比例的高质量缩略图

作者：孟宪会阅读：552 发表于：2011-12-10 23:41:14

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>

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