Question

I a function belows which is being used to preview an image but that involves saving the image locally in my drive. I am using this feature in an data entry form which means if the user discards the form, I have to delete the image which I feel is not efficient. How can I go about previewing the image and only save it locally if the user saves the form. Thanks.

 Protected Sub save_btn_Click(ByVal sender As Object, ByVal e As EventArgs) Handles btn_Save.Click
        If uifuVouTypeUploadfile.PostedFile IsNot Nothing Then
            ' Check file size (mustn’t be 0)
            Dim myFile As HttpPostedFile = uifuVouTypeUploadfile.PostedFile
            Dim nFileLen As Integer = myFile.ContentLength
            If nFileLen = 0 Then
                'rqfvVouImage.ErrorMessage = "No file was uploaded."
                'rqfvVouImage.IsValid = False
                Return
            End If
            ' Check file extension (must be JPG)
            If System.IO.Path.GetExtension(myFile.FileName).ToLower() <> ".jpg" AndAlso System.IO.Path.GetExtension(myFile.FileName).ToLower() <> ".gif" AndAlso System.IO.Path.GetExtension(myFile.FileName).ToLower() <> ".bmp" Then
                'rqfvVouImage.ErrorMessage = "The file must have an extension of JPG or GIF"
                'rqfvVouImage.IsValid = False
                Return
            Else
                myFile.SaveAs(MapPath(System.IO.Path.GetFileName(myFile.FileName).ToLower().ToString()))
                'Show the uploaded resized picture in the image control
                uiimgVouImage.ImageUrl = System.IO.Path.GetFileName(myFile.FileName).ToLower().ToString()
            End If
        End If
    End Sub

Answer 1

You may construct the Bitmap object of uploaded file and write it to Response stream.

Bitmap bmp = new Bitmap(uifuVouTypeUploadfile.PostedFile.InputStream);
bmp.Save(Response.OutputStream, System.Drawing.Imaging.ImageFormat.Jpeg);
Response.Flush();
Response.End();

Take a look at these posts:

1. How to show the selected image file without saving file in the disk before upload
2. Image preview before uploading using AsynFileUpload