c multi image upload and generate thumbnail example code
- 2020-06-03 06:15:38
- OfStack
Foreground code:
<%@ 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=" To upload " />
</li>
</ul>
</div>
</form>
</body>
</html>
The foreground is just a few controls and an ValidImage method.
Background code:
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); // The current upload control ID, because jquery I'm going to call it #
string msg = null; // Prompt information
if (postFile.FileName.Trim().Length <= 0)
{
continue;
}
if (postFile.ContentLength > size)
{
msg = " The file is too large ";
Page.ClientScript.RegisterStartupScript(GetType(), "", "ValidImage(" + uploadFileID + "," + msg + ")", true);// Send the prompt message to the client
continue;
}
string savePath = Path.Combine(filePath, postFile.FileName); // The save address of the picture
if (!File.Exists(savePath))
{
postFile.SaveAs(Path.Combine(filePath, postFile.FileName)); // If the file does not exist, save it
}
else
{
msg = " file " + postFile.FileName + " existing ";
Page.ClientScript.RegisterStartupScript(GetType(), "", "ValidImage(" + uploadFileID + "," + msg + ")", true);// Send the prompt message to the client
continue;
}
if (IsImg(savePath)) // through IsImg Method to verify that the file is an image or formatted correctly
{
SmallImg(postFile.InputStream, postFile.FileName);
}
else
{
msg = " Can only upload JGP , PNG Type of image, please check the file format is correct ";
Page.ClientScript.RegisterStartupScript(GetType(), "", "ValidImage(" + uploadFileID + "," + msg + ")", true);// Send the prompt message to the client
File.Delete(savePath); // If it's not, delete it
}
}
}
}
#region Verify the format of the uploaded file
/// <summary>
/// Verify that the uploaded file is an image
/// </summary>
/// <param name="FilePath"> The save path for the file </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")// instructions 255216 is jpg;7173 is gif;6677 is BMP,13780 is PNG;7790 is exe,8297 is rar
{
result = true;
}
return result;
}
}
#endregion
#region Generate a thumbnail of the image
/// <summary>
/// Generate thumbnails
/// </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); // Thumbnail name
string filePath = Server.MapPath("/uploadImg/") + newFileName;
bmp.Save(filePath);
}
}
}
}
#endregion
The code has a lot to improve, I hope you can give me some advice.