Exercise
Reading a binay file (2 - GIF)
Objetive
Create a Visual Basic (VB.Net) program to check if a GIF image file seems to be correct.
It must see if the first four bytes are G, I, F, 8.
In case it seems correct, it must also display the GIF version (87 or 89), checking if the following byte is a 7 or a 9.
Code
Imports System
Imports System.IO
Public Class GifFile
Public Shared Sub Main()
Dim data As Byte() = New Byte(4) {}
Dim file As BinaryReader = New BinaryReader(File.Open("test.gif", FileMode.Open))
For i As Integer = 0 To 5 - 1
data(i) = file.ReadByte()
Next
file.Close()
If data(0) = Convert.ToByte("G"c) AndAlso data(1) = Convert.ToByte("I"c) AndAlso data(2) = Convert.ToByte("F"c) AndAlso data(3) = Convert.ToByte("8"c) Then
Console.WriteLine("Its a GIF8" & data(4))
Else
Console.WriteLine("It not gif file")
End If
End Sub
End Class