c#多图片上传并生成缩略图的实例代码
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。