Asp.net generates thumbnails and supports file upload implementation code

This article shares the asp.net implementation code that automatically generates thumbnails after two files are uploaded. The benefits of thumbnails can reduce server bandwidth and speed up image download.

 

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 Layer 3 { /// <Summary> /// Display the thumbnail of the requested image, in the maximum unit of 100 pixels in width /// </Summary> Public class imgSmall: IHttpHandler { // Folder where the image is located Static string picturesPath = @ "d: wordpictures "; Public void ProcessRequest (HttpContext context) { Context. Response. ContentType = "image/jpeg "; // Obtain the passed img string, such // Http: // localhost: 5002/imgSmall. ashx? Img1_abacus8.jpg String img = context. Request. Params ["img"]; String path = picturesPath + img; // If the file exists, it will be read. Reduce the use of try and catch to improve program performance. If (File. Exists (path )) { // Load the image Image big = Image. FromFile (path ); // If the file can be obtained, the following code will be executed. If (big! = Null) { // Set the maximum width, which can be modified to generate smaller thumbnails Int newWidth = 100; // Generate a bitmap based on the aspect ratio of the image. Bitmap bitmap = new Bitmap (newWidth, newWidth * big. Height/big. Width ); // Create a picture based on the palette Graphics g = Graphics. FromImage (bitmap ); Using (g) { // Draw a big image to a bitmap defined by yourself G. DrawImage (big, 0, 0, bitmap. Width, bitmap. Height ); // Directly Save the processed bitmap to the response output stream. The format is jpeg! Bitmap. Save (context. Response. OutputStream, System. Drawing. Imaging. ImageFormat. Jpeg ); } } } Else { // Otherwise, a message indicating that the file does not exist will be sent to the browser. Context. Response. ContentType = "text/html "; Context. Response. Write ("the file does not exist "); // Or send an image that does not exist in the file // Context. Response. WriteFile ("Change todo to image path "); } } Public bool IsReusable { Get { Return false; } } } }

Instance, you can upload the image and then generate a thumbnail

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 = "Size of the uploaded file" + 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 string Dim id as integer Dim image, anewimage As System. Drawing. Image Dim width, height, newwidth, newheight as integer Dim callb As System. Drawing. Image. GetThumbnailImageAbort MyConn = New sqlconnection (ConfigurationSettings. deleettings ("Database ")) Myconn. open () SQL = "insert into picture (name, class, Introduction, attribute) values ('" & request. cookies ("dgxyl "). values ("dgxylname") & "','" & request. cookies ("dgxyl "). values ("dgxylbj") & "','" & trim (request ("TextBox1") & "','" & request ("r1 ")&"')" Mycomm = New sqlcommand (SQL, myconn) Mycomm.exe cutenonquery () 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.exe cutereader () If myReader. Read () then Id = myReader ("id ") End if Myconn. close () 'Save the image FileUp. PostedFile. SaveAs (Server. MapPath ("classpic") & cstr (id) & ". jpg ") 'Generate a thumbnail 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. Length-1 )) FDisplay. text = "<A Target = '_ blank' HREF = '/classpic/" & cstr (id )&". jpg "&" '> View uploaded files </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 whether the request is submitted again If (requestsubmitted = true ){ Alert ("You have submitted a message. Please wait for the server to respond! "); Return (false ); } Requestsubmitted = true; Return (true ); } // --> </SCRIPT> <Html> <Body BgColor = White> <H3 align = "center"> enter the following items correctly <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"> Upload files <Input Type = "File" id = "FileUp" runat = "server" size = "20"> <br> Image attribute: <input type = "radio" value = "<% = request. cookies ("dgxyl "). values ("dgxylbj ") %> "name =" R1 "checked> This class <input type =" radio "value =" "name =" R1 "> all schools (this class is only displayed in this class, the whole school is displayed in the whole school.) <P> Image Description: <br> <Asp: TextBox id = "TextBox1" runat = "server" Width = "233px" Height = "141px"> </Asp: TextBox> <Asp: RequiredFieldValidator id = "RequiredFieldValidator1" runat = "server" ControlToValidate = "TextBox1" ErrorMessage = "Enter image description"> </Asp: RequiredFieldValidator> <br> <Asp: button id = "Upload" Text = "Upload image" runat = "server"/> </Form> <Hr> <P> Note: </p> <Ol> <Li> <B> It is strictly prohibited to upload photos that pollute the environment. Otherwise, the account will be deleted! </B> </li> <Li> <font color = "#808000"> <B> Fill in the photo description in detail. If the picture description is not detailed, it will be regarded as a false picture and will be deleted! </B> </font> </li> </Ol> </Body> </Html>