c#怎么实现多图片上传并生成缩略图
这篇文章主要介绍"c#怎么实现多图片上传并生成缩略图"，在日常操作中，相信很多人在c#怎么实现多图片上传并生成缩略图问题上存在疑惑，小编查阅了各式资料，整理出简单好用的操作方法，希望对大家解答"c#怎么实现多图片上传并生成缩略图"的疑惑有所帮助！接下来，请跟着小编一起来学习吧！
前台代码:
复制代码 代码如下:
<%@ Page Language="C#" AutoEventWireup="true" CodeFile="upload.aspx.cs" Inherits="upload" %>
前台就是几个控件和一个ValidImage方法。
后台代码：
复制代码 代码如下:
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
}
}
}
}
复制代码 代码如下:
#region 验证上传文件的格式
///
/// 验证上传文件是否是图片
///
/// 文件的保存路径
///
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
复制代码 代码如下:
#region 将图片生成缩略图
///
/// 生成缩略图
///
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
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