How to create thumbnail of images in asp.net vb.net

In this article I have created thumbnails from large images using coding. This code will help how to make thumbnail images before to upload on the server You can specify the size like height and width of the thumbnail images.

you can save thumbnail images in thumbnail folder and if you need to display the full image after click on the thubnail then you can save full image in image folder..

its all about your logic and what you wants to do.

hope it will help you…

( i have coded in c# too)

Imports System.IO

Imports System.Drawing

Imports System.Drawing.Image

Imports System.Drawing.Imaging

Partial Class Default2

Inherits System.Web.UI.Page

Public Function ThumbnailCallback() As Boolean

Return (False)

End Function

Protected Sub Button2_Click(ByVal sender As Object, ByVal e As System.EventArgs) Handles Button2.Click

If img_upload.PostedFile.ContentLength > 0 Then

Dim UploadedFileName As String

UploadedFileName = img_upload.PostedFile.FileName

img_upload.PostedFile.SaveAs(Request.PhysicalApplicationPath & “images/” & UploadedFileName)

Dim size As Image = Image.FromFile(Request.PhysicalApplicationPath & “images/” & UploadedFileName)

Dim h As Int32 = size.Height

Dim w As Int32 = size.Width

‘ You can check the size of the image after upload on the server if that file according to yur dimension then it will submit and will create the thumbnail of the images other wise it will delete from the server.

If (w >= 300 And w <= 1024) And (h >= 30 And h <= 768) Then Label1.Text = “Submit” Else Label1.Text = “Error” size.Dispose() ‘ the image is not in actual range of size then delete it from images folder File.Delete(Server.MapPath(“images”) + “/” + UploadedFileName) Exit Sub End If Try ‘Read in the image filename whose thumbnail has to be created Dim imageurl As String = UploadedFileName ‘Read in the width and height Dim height As Int32 = 175 Dim width As Int32 = 180 If (imageurl.IndexOf(“/”) >= 0) Or (imageurl.IndexOf(“\\”) > 0) Then

Response.End()

End If

imageurl = “images\” + imageurl

Dim fullSizeImg As System.Drawing.Image = System.Drawing.Image.FromFile(Server.MapPath(imageurl))

Dim dummyCallBack As New System.Drawing.Image.GetThumbnailImageAbort(AddressOf ThumbnailCallback) ‘Delegate will call the method ThumbnailCallback

Dim thumbNailImg As System.Drawing.Image = fullSizeImg.GetThumbnailImage(width, height, dummyCallBack, IntPtr.Zero)

‘We need to create a unique filename for each generated image

Dim MyDate As DateTime = DateTime.Now

Dim MyString As String = UploadedFileName

‘Save the thumbnail in Png format. You may change it to a diff format with the ImageFormat property

thumbNailImg.Save((Request.PhysicalApplicationPath & “Thumb_images\”) + MyString, ImageFormat.Jpeg) ‘ for imageformat add ”Imports System.Drawing.Imaging

thumbNailImg.Dispose()

Catch ex As Exception

Label.text =”error message”

End Try

Else

End If

End Sub

End Class

With Regards

Vik