asp.net generates thumbnails and supports file upload implementation code

The code is as follows

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Using System; Using System.Collections.Generic; Using System.Linq; Using System.Web; Using System.Drawing; Using System.IO; Namespace Web three layer { <summary> Displays the thumbnail of the requested picture, with a width of 100 pixels as the largest unit </summary> public class Imgsmall:ihttphandler { folder where pictures are located static string Picturespath = @ "D:wordpictures"; public void ProcessRequest (HttpContext context) { Context. Response.ContentType = "Image/jpeg"; Gets the IMG string passed over, such as Yun_qi_img/imgsmall.ashximg=abacus8.jpg this string img = context. Request.params["IMG"]; String path = Picturespath + img; If the file exists to read, reduce the use of Try,catch, improve program performance if (file.exists (path)) { Load this picture Image big = image.fromfile (path); If you can get a file, the following code is executed if (Big!= null) { Set the maximum width and can be modified to produce smaller thumbnails int newwidth = 100; Generate a bitmap based on the aspect ratio of the picture Bitmap Bitmap = new Bitmap (newwidth, Newwidth * big. Height/big. Width); To create a picture from a storyboard Graphics g = graphics.fromimage (bitmap); Using (g) { Draw big picture into your own little map of your definition bitmap G.drawimage (big, 0, 0, bitmap.) Width, Bitmap. Height); Directly saves the processed bitmap to the response output stream in the form of jpeg! Bitmap. Save (context. Response.outputstream, System.Drawing.Imaging.ImageFormat.Jpeg); } } } Else { Otherwise, send a file that does not exist to the browser Context. Response.ContentType = "text/html"; Context. Response.Write ("File does not exist"); Or send a picture of a file that doesn't exist Context. Response.WriteFile ("Todo here modified as the path to the picture"); } } public bool IsReusable { Get { return false; } } } }

example, you can upload pictures and then generate thumbnails

The code is as follows

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<script language= "VB" runat= "Server" > Sub UploadFile (sender as Object, E as EventArgs) If FileUp.PostedFile.ContentLength = 0 Then Fileinfo.visible = False Exit Sub Else Fileinfo.visible = True Fdisplay1.visible = True End If Fsize.text = "Upload file size" + CSTR (fileup.postedfile.contentlength/1024) + "KB" Fname.text = "uploaded file name:" +fileup.postedfile.filename+ "<br>" +fname.text ' write to database On Error Resume Next Dim myconn As SqlConnection Dim mycomm As SqlCommand Dim sql As St Ring Dim id As Integer Dim image,anewimage As System.Drawing.Image Dim width,height,newwidth,newheight As I Nteger Dim callb as System.Drawing.Image.GetThumbnailImageAbort Myconn=new SqlConnection ( ConfigurationSettings.AppSettings ("database")) MyConn.Open () sql= "insert into the picture (name, class, description, Attributes) VALUES ('" &request.cookies ("Dgxyl"). VALUES ("Dgxylname") & "', '" &request.cookies ("Dgxyl"). VALUES ("DGXYLBJ") & "', '" &trim (Request ("TextBox1")) & "', '" &request ("R1") & "')" Mycomm=new SqlCommand (sql, myconn) Mycomm.executenonquery () Myconn.close () Dim mycommand as New SqlCommand ("SELECT top 1 ID from picture ORDER by id Desc", myconn) MyCommand.Connection.Open () Dim myreader as Sqldatareader=mycommand.executereader () if Myreader.read () then Id=myreader ("id") E nd if myconn.close () Save picture FileUp.PostedFile.SaveAs (Server.MapPath ("Classpic") &cstr (ID) & ". jpg" Generate thumbnails Image=system.drawing.image.fromfile (Server.MapPath ("/classpic/" +cstr (ID) + ". jpg") Width= Image. Width Height=image.height If Width>height then newwidth=250 Newheight=image.height/image. Width*newwidth Else newheight=250 Newwidth=image. Width/image.height*newheight End If Response.Write ("id=" +cstr (ID) + width= "+cstr" (width) + "; height=" +cstr ( Height) + " ") Response.Write ("Newwidth=" +cstr (newwidth) + "; newheight=" +cstr (newheight) + "<br>") Anewimage=image. Getthumbnailimage (Newwidth,newheight,callb,new system.intptr ()) Anewimage.save (Server.MapPath ("/smallpic/" +cstr (ID) + ". jpg") Image. Dispose () Dim Filesplit () as String = Split (FileUp.PostedFile.FileName, "") Dim FileName as String = Filesplit (filesplit.length-1) Dim exts () as String = Split (FileName, ".") Dim Ext as String = LCase (exts (exts.length-1)) Fdisplay.text = "<a target= ' _blank ' href= '/classpic/" &cstr (ID) & ". jpg" & "> View upload file </A>" fdisplay1.text= "<a href= '/picture/default.asp?bj=" &cstr (Request.Cookies ("Dgxyl"). VALUES ("DGXYLBJ") & "' > Return </a>" End Sub </script> <script language=javascript> <!-- var Requestsubmitted=false; function Guestbook_validator (theform) { Check to see if you are submitting a new if (requestsubmitted==true) { Alert ("You have submitted a message, please wait for the server to reply!") "); return (false); } Requestsubmitted=true; return (true); } --> </SCRIPT> <Html> <body bgcolor=white> <Hr></H3> <div id= "FileInfo" visible= "False" runat= "Server" > <asp:label id= "fsize" runat= "Server"/><br> <asp:label id= "FName" runat= "Server"/><br> <asp:label id= "Fdisplay" runat= "Server"/> <asp:label id= "FDisplay1" runat= "Server"/> </Div> <form enctype= "Multipart/form-data" onsubmit= "return Guestbook_validator (This)" runat= "Server" > Uploading files <input type= "File" id= "Fileup" runat= "Server" size= "><br>" Picture properties: <input type= "Radio" value= <%=request.cookies ("Dgxyl"). VALUES ("DGXYLBJ")%> "name=" R1 "checked>" <input type= "Radio" value= "The whole School" name= "R1" > School (This class is only shown in this class, the whole school is shown in the whole school) <P> Picture Description:<br> <asp:textbox id= "TextBox1" runat= "Server" width= "233px" height= "141px" > </asp:TextBox> <asp:requiredfieldvalidator id= "RequiredFieldValidator1" runat= "Server" controltovalidate= "TextBox1" Errormessage= "Please enter picture description" > </asp:RequiredFieldValidator><br> <asp:button id= "Upload" text= "Upload Picture" runat= "Server"/> </form> <Hr> <p> Note:</p> <ol> <li><b> do not upload photos of contaminated environment, otherwise the account will be deleted! </b></li> <li><font color= "#808000" ><b> please fill in the photo description, the picture description is not detailed will be considered as a random image, will be deleted! </b></font></li> </ol> </Body> </Html>