This is a Brute-force-and-ingorance approach, but...try:
Dim path As String = "D:\Temp\MyPic.jpg"
Dim startdata As Byte = &Hff
Dim enddata As Byte = &H0
Dim data As Byte() = File.ReadAllBytes(path)
Dim extract As Byte()
Dim startIndex As Integer
For startIndex = 0 To data.Length - 1
If data(startIndex) = startdata Then
Exit For
End If
Next
startIndex += 1
Dim endIndex As Integer
For endIndex = startIndex To data.Length - 1
If data(endIndex) = enddata Then
Exit For
End If
Next
extract = New Byte(endIndex - startIndex - 1) {}
Array.Copy(data, startIndex, extract, 0, endIndex - startIndex)