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Steganography Help
Hello all,
I am fairly new to VB.Net but have been using vb5/6 for a while. I am after some help with the following
Code:
Public Sub PicText(ByVal cmd As String, ByVal picpath As String)
Dim PicBuffer As New System.IO.FileInfo(picpath)
Dim Ready As Boolean = True
Dim PicFileStream As System.IO.FileStream
Try
PicFileStream = PicBuffer.OpenRead
Catch ex As Exception
End Try
If Ready = True Then
Dim PicBytes As Long = PicFileStream.Length
Dim PicExt As String = PicBuffer.Extension
PicBuffer = Nothing
Dim PicByteArray(PicBytes) As Byte
PicFileStream.Read(PicByteArray, 0, PicBytes)
PicFileStream.Close()
PicFileStream.Dispose()
Dim SentinelString() As Byte = {73, 116, 83, 116, 97, 114, 116, 115, 72, 101, 114, 101}
If cmd = "Write" Then
Dim PlainText As String = frmInfo.txtImageInfo.Text
Dim PlainTextByteArray(PlainText.Length) As Byte
For i As Integer = 0 To (PlainText.Length - 1)
PlainTextByteArray(i) = CByte(AscW(PlainText.Chars(i)))
Application.DoEvents()
Next
Dim PicAndText(PicBytes + PlainText.Length + SentinelString.Length) As Byte
For t As Long = 0 To (PicBytes - 1)
PicAndText(t) = PicByteArray(t)
Next
Dim count As Integer = 0
For r As Long = PicBytes To (PicBytes + (SentinelString.Length) - 1)
PicAndText(r) = SentinelString(count)
count += 1
Next
count = 0
For q As Long = (PicBytes + SentinelString.Length) To (PicBytes + SentinelString.Length + PlainText.Length - 1)
PicAndText(q) = PlainTextByteArray(count)
count += 1
Next
My.Computer.FileSystem.WriteAllBytes(picpath, PicAndText, False)
PlainText = Nothing
PicAndText = Nothing
PlainTextByteArray = Nothing
PicByteArray = Nothing
ElseIf cmd = "Read" Then
Dim OutterSearch, InnerSearch, StopSearch As Boolean
OutterSearch = True
InnerSearch = True
StopSearch = False
Dim count As Long = 0
Dim leftCounter As Long
Dim rightCounter As Integer
leftCounter = 0
rightCounter = 0
Do While (count < (PicBytes - SentinelString.Length) And StopSearch = False)
If (PicByteArray(count) = SentinelString(0)) Then
leftCounter = count + 1
rightCounter = 1
InnerSearch = True
Do While (InnerSearch = True) And (rightCounter < SentinelString.Length) _
And (leftCounter < PicByteArray.Length)
If (PicByteArray(leftCounter) = SentinelString(rightCounter)) Then
rightCounter += 1
leftCounter += 1
If (rightCounter = (SentinelString.Length - 1)) Then
StopSearch = True
End If
Else
InnerSearch = False
count += 1
End If
Loop
Else
count += 1
End If
Loop
If StopSearch = True Then
'leftCounter contains the starting string that is being retrieved
Do While (leftCounter < PicBytes)
'Bytes need to be converted to an integer
'then to an unicode character which will be the plaintext
frmInfo.txtImageInfo.AppendText(ChrW(CInt(PicByteArray(leftCounter))))
leftCounter += 1
Loop
PicByteArray = Nothing
PicBytes = Nothing
End If
ElseIf cmd = "Delete" Then
Dim OutterSearch, InnerSearch, StopSearch As Boolean
OutterSearch = True
InnerSearch = True
StopSearch = False
Dim count As Long = 0
Dim leftCounter As Long
Dim rightCounter As Integer
leftCounter = 0
rightCounter = 0
Do While (count < (PicBytes - SentinelString.Length) And StopSearch = False)
If (PicByteArray(count) = SentinelString(0)) Then
leftCounter = count + 1
rightCounter = 1
InnerSearch = True
Do While (InnerSearch = True) And (rightCounter < SentinelString.Length) _
And (leftCounter < PicByteArray.Length)
If (PicByteArray(leftCounter) = SentinelString(rightCounter)) Then
rightCounter += 1
leftCounter += 1
If (rightCounter = (SentinelString.Length - 1)) Then
StopSearch = True
End If
Else
InnerSearch = False
count += 1
End If
Loop
Else
count += 1
End If
Loop
If StopSearch = True Then
Dim newfile(count) As Byte
For i As Long = 0 To count - 1
newfile(i) = PicByteArray(i)
Next
My.Computer.FileSystem.WriteAllBytes(picpath, newfile, False)
End If
End If
End If
End Sub
I am trying to place text into an image, beable to delete/modify the text and then write it to THE SAME filename. I can get this to work to a different filename with no troubles but not the same. I get a "file being used by another process" error. I know my prog is the only thing accessing the file. Any suggestions???
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I don't get the error. I made some insignificant changes to your code (select case, error handling, Longs to Integers, different form reference). I'm using VS2008
Code:
Public Sub PicText(ByVal cmd As String, ByVal picpath As String)
Dim PicBuffer As New System.IO.FileInfo(picpath)
Dim Ready As Boolean = True
Dim PicFileStream As System.IO.FileStream = PicBuffer.OpenRead
If Ready = True Then
Dim PicBytes As Integer = CType(PicFileStream.Length, Integer)
Dim PicExt As String = PicBuffer.Extension
PicBuffer = Nothing
Dim PicByteArray(PicBytes) As Byte
PicFileStream.Read(PicByteArray, 0, PicBytes)
PicFileStream.Close()
PicFileStream.Dispose()
Dim SentinelString() As Byte = {73, 116, 83, 116, 97, 114, 116, 115, 72, 101, 114, 101}
Select Case cmd
Case "Write"
Try
Dim PlainText As String = Me.txtImageInfo.Text
Dim PlainTextByteArray(PlainText.Length) As Byte
For i As Integer = 0 To (PlainText.Length - 1)
PlainTextByteArray(i) = CByte(AscW(PlainText.Chars(i)))
Application.DoEvents()
Next
Dim PicAndText(PicBytes + PlainText.Length + SentinelString.Length) As Byte
For t As Integer = 0 To (PicBytes - 1)
PicAndText(t) = PicByteArray(t)
Next
Dim count As Integer = 0
For r As Integer = PicBytes To (PicBytes + (SentinelString.Length) - 1)
PicAndText(r) = SentinelString(count)
count += 1
Next
count = 0
For q As Integer = (PicBytes + SentinelString.Length) To (PicBytes + SentinelString.Length + PlainText.Length - 1)
PicAndText(q) = PlainTextByteArray(count)
count += 1
Next
My.Computer.FileSystem.WriteAllBytes(picpath, PicAndText, False)
PlainText = Nothing
PicAndText = Nothing
PlainTextByteArray = Nothing
Catch ex As Exception
MessageBox.Show(ex.ToString, "PicText " & cmd & " Error", MessageBoxButtons.OK, MessageBoxIcon.Error)
End Try
PicByteArray = Nothing
Case "Read"
Try
Dim OutterSearch, InnerSearch, StopSearch As Boolean
OutterSearch = True
InnerSearch = True
StopSearch = False
Dim count As Integer = 0
Dim leftCounter As Integer
Dim rightCounter As Integer
leftCounter = 0
rightCounter = 0
Do While (count < (PicBytes - SentinelString.Length) And StopSearch = False)
If (PicByteArray(count) = SentinelString(0)) Then
leftCounter = count + 1
rightCounter = 1
InnerSearch = True
Do While (InnerSearch = True) And (rightCounter < SentinelString.Length) _
And (leftCounter < PicByteArray.Length)
If (PicByteArray(leftCounter) = SentinelString(rightCounter)) Then
rightCounter += 1
leftCounter += 1
If (rightCounter = (SentinelString.Length - 1)) Then
StopSearch = True
End If
Else
InnerSearch = False
count += 1
End If
Loop
Else
count += 1
End If
Loop
If StopSearch = True Then
'leftCounter contains the starting string that is being retrieved
Do While (leftCounter < PicBytes)
'Bytes need to be converted to an integer
'then to an unicode character which will be the plaintext
Me.txtImageInfo.AppendText(ChrW(CInt(PicByteArray(leftCounter))))
leftCounter += 1
Loop
PicByteArray = Nothing
PicBytes = Nothing
End If
Catch ex As Exception
MessageBox.Show(ex.ToString, "PicText " & cmd & " Error", MessageBoxButtons.OK, MessageBoxIcon.Error)
End Try
Case "Delete"
Try
Dim OutterSearch, InnerSearch, StopSearch As Boolean
OutterSearch = True
InnerSearch = True
StopSearch = False
Dim count As Integer = 0
Dim leftCounter As Integer
Dim rightCounter As Integer
leftCounter = 0
rightCounter = 0
Do While (count < (PicBytes - SentinelString.Length) And StopSearch = False)
If (PicByteArray(count) = SentinelString(0)) Then
leftCounter = count + 1
rightCounter = 1
InnerSearch = True
Do While (InnerSearch = True) And (rightCounter < SentinelString.Length) _
And (leftCounter < PicByteArray.Length)
If (PicByteArray(leftCounter) = SentinelString(rightCounter)) Then
rightCounter += 1
leftCounter += 1
If (rightCounter = (SentinelString.Length - 1)) Then
StopSearch = True
End If
Else
InnerSearch = False
count += 1
End If
Loop
Else
count += 1
End If
Loop
If StopSearch = True Then
Dim newfile(count) As Byte
For i As Integer = 0 To count - 1
newfile(i) = PicByteArray(i)
Next
My.Computer.FileSystem.WriteAllBytes(picpath, newfile, False)
End If
Catch ex As Exception
MessageBox.Show(ex.ToString, "PicText " & cmd & " Error", MessageBoxButtons.OK, MessageBoxIcon.Error)
End Try
End Select
End If
End Sub
How are you calling your Sub?
...joe
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This is only a guess, but because it looks like VB still has your file locked up, at least for write, that it may be your FileInfo object. You closed and disposed of the ReadOnly file stream, but not the FileInfo object.
Dim PicBuffer As New System.IO.FileInfo(picpath) '<-- accessing your file
Since WriteAllBytes want's to overwrite the file, it may not be able to until all objects referencing it are closed or at least no longer referencing that file.
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