c#多图片上传并生成缩略图的实例代码
2019/7/7 18:31:51
本文主要是介绍c#多图片上传并生成缩略图的实例代码，对大家解决编程问题具有一定的参考价值，需要的程序猿们随着小编来一起学习吧！
前台代码:
<%@ Page Language="C#" AutoEventWireup="true" CodeFile="upload.aspx.cs" Inherits="upload" %>
<!DOCTYPE html>
<html xmlns="http://www.w3.org/1999/xhtml">
<head runat="server">
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<title></title>
<style type="text/css">
li
{
list-style: none;
padding-top: 10px;
}
</style>
<script type="text/javascript" src="js/jquery-1.6.2.min.js"></script>
<script type="text/javascript">
function ValidImage(id, msg) {
$(id).parent().append("<span>" + msg + "</span>");
return false;
}
</script>
</head>
<body>
<form id="form1" runat="server" enctype="multipart/form-data" method="post">
<div>
<ul>
<li>
<input type="file" id="upload1" name="upload" />
</li>
<li>
<input type="file" id="upload2" name="upload" />
</li>
<li>
<input type="file" id="upload3" name="upload" />
</li>
<li>
<input type="file" id="upload4" name="upload" /></li>
<li>
<input type="file" id="upload5" name="upload" />
</li>
<li>
<input type="submit" id="btnPostFile" runat="server" onserverclick="btnPostFile_ServerClick" value="开始上传" />
</li>
</ul>
</div>
</form>
</body>
</html>
前台就是几个控件和一个ValidImage方法。
后台代码：
protected void btnPostFile_ServerClick(object sender, EventArgs e)
{
string filePath = Server.MapPath("/uploadImg");
const int size = 5242880;
if (!Directory.Exists(filePath))
{
Directory.CreateDirectory(filePath);
}
if (Request.Files.Count > 0)
{
for (int i = 0; i < Request.Files.Count; i++)
{
HttpPostedFile postFile = Request.Files[i];
string uploadFileID = string.Format("#upload{0}", i + 1); //当前的上传控件ID,因为jquery要调用就加了#
string msg = null; //提示信息
if (postFile.FileName.Trim().Length <= 0)
{
continue;
}
if (postFile.ContentLength > size)
{
msg = "文件太大";
Page.ClientScript.RegisterStartupScript(GetType(), "", "ValidImage(" + uploadFileID + "," + msg + ")", true);//将提示信息发送到客户端
continue;
}
string savePath = Path.Combine(filePath, postFile.FileName); //图片的保存地址
if (!File.Exists(savePath))
{
postFile.SaveAs(Path.Combine(filePath, postFile.FileName)); //如果文件不存在就保存
}
else
{
msg = "文件" + postFile.FileName + "已经存在";
Page.ClientScript.RegisterStartupScript(GetType(), "", "ValidImage(" + uploadFileID + "," + msg + ")", true);//将提示信息发送到客户端
continue;
}
if (IsImg(savePath)) //通过IsImg方法验证文件是否是图片，或者格式是否正确
{
SmallImg(postFile.InputStream, postFile.FileName);
}
else
{
msg = "只能上传JGP、PNG类型的图片，请检查文件格式是否正确";
Page.ClientScript.RegisterStartupScript(GetType(), "", "ValidImage(" + uploadFileID + "," + msg + ")", true);//将提示信息发送到客户端
File.Delete(savePath); //如果不是图片就删除
}
}
}
}
#region 验证上传文件的格式
/// <summary>
/// 验证上传文件是否是图片
/// </summary>
/// <param name="FilePath">文件的保存路径</param>
/// <returns></returns>
private bool IsImg(string FilePath)
{
using (FileStream fs = new FileStream(FilePath, FileMode.Open, FileAccess.Read))
{
bool result = false;
BinaryReader br = new BinaryReader(fs, System.Text.Encoding.UTF8);
string strImg = "";
byte buffer;
try
{
buffer = br.ReadByte();
strImg = buffer.ToString();
buffer = br.ReadByte();
strImg += buffer.ToString();
}
catch
{
fs.Close();
br.Close();
}
if (strImg == "255216" || strImg == "13780")//说明255216是jpg;7173是gif;6677是BMP,13780是PNG;7790是exe,8297是rar
{
result = true;
}
return result;
}
}
#endregion
#region 将图片生成缩略图
/// <summary>
/// 生成缩略图
/// </summary>
private void SmallImg(Stream oStream, string FileName)
{
using (System.Drawing.Image img = System.Drawing.Image.FromStream(oStream))
{
int newWidth = 100;
int newHeight = 80;
int oldWidth = img.Width;
int oldHeight = img.Height;
if (oldWidth > oldHeight)
{
newHeight = (int)Math.Floor((double)oldHeight * (double)newWidth / (double)oldWidth);
}
else
{
newWidth = (int)Math.Floor((double)oldWidth * (double)newHeight / (double)oldHeight);
}
using (Bitmap bmp = new Bitmap(newWidth, newHeight))
{
using (Graphics g = Graphics.FromImage(bmp))
{
g.Clear(Color.Transparent);
g.InterpolationMode = InterpolationMode.High;
g.CompositingQuality = CompositingQuality.HighQuality;
g.SmoothingMode = SmoothingMode.HighQuality;
g.DrawImage(img, new Rectangle(0, 0, newWidth, newHeight), new Rectangle(0, 0, oldWidth, oldHeight), GraphicsUnit.Pixel);
string newFileName = Path.GetFileNameWithoutExtension(FileName) + "_small" + Path.GetExtension(FileName); //缩略图名称
string filePath = Server.MapPath("/uploadImg/") + newFileName;
bmp.Save(filePath);
}
}
}
}
#endregion
代码有很多需要改进的地方，希望大家多多指点。
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