BMP width & height, FileStream

Lesson

File Management

Exercise

Objetive

Create a Visual Basic (VB.Net) program to display the width and height of a BMP file using a FileStream.

Remember the structure of the BMP header:

File type (letters BM)
0-1

File Size
2-5

Reserved
6-7

Reserved
8-9

Start of image data
10-13

Size of bitmap header
14-17

Width (pixels)
18-21

Height (pixels)
22-25

Number of planes
26-27

Size of each point
28-29

Compression (0=not compressed)
30-33

Image size
34-37

Horizontal resolution
38-41

Vertical resolution
42-45

Size of color table
46-49

Important colors counter
50-53

Code

Imports System
Imports System.IO
Public Class exercise188
    Public Shared Sub Main()
        Dim myFile As FileStream
        Dim data As Byte()
        Dim width, height As Integer
        Const SIZE As Integer = 54
        Console.Write("Enter the name of file: ")
        Dim fileName As String = Console.ReadLine()

If Not File.Exists(fileName) Then
            Console.WriteLine("The file not exists!!!")
            Return
        End If

Try
            myFile = File.OpenRead(fileName)
            data = New Byte(53) {}
            myFile.Read(data, 0, SIZE)
            myFile.Close()
            Dim b1 As Byte = data(0)
            Dim b2 As Byte = data(1)

If (Convert.ToChar(b1) <> "B"c) OrElse (Convert.ToChar(b2) <> "M"c) Then
                Console.WriteLine("This File is NOT a BMP file")
                Return
            End If

width = data(18) + (data(19) * 256) + (data(20) * 256 * 256) + (data(21) * 256 * 256 * 256)
            height = data(22) + (data(23) * 256) + (data(24) * 256 * 256) + (data(25) * 256 * 256 * 256)
            Console.WriteLine("Width: {0} - Heigth: {1}", width, height)
        Catch e As Exception
            Console.WriteLine("Error: {0}!!!", e.message())
        End Try
    End Sub
End Class

Imports System
Imports System.IO
Public Class exercise188
    Public Shared Sub Main()
        Dim myFile As FileStream
        Dim data As Byte()
        Dim width, height As Integer
        Const SIZE As Integer = 54
        Console.Write("Enter the name of file: ")
        Dim fileName As String = Console.ReadLine()

        If Not File.Exists(fileName) Then
            Console.WriteLine("The file not exists!!!")
            Return
        End If

        Try
            myFile = File.OpenRead(fileName)
            data = New Byte(53) {}
            myFile.Read(data, 0, SIZE)
            myFile.Close()
            Dim b1 As Byte = data(0)
            Dim b2 As Byte = data(1)

            If (Convert.ToChar(b1) <> "B"c) OrElse (Convert.ToChar(b2) <> "M"c) Then
                Console.WriteLine("This File is NOT a BMP file")
                Return
            End If

            width = data(18) + (data(19) * 256) + (data(20) * 256 * 256) + (data(21) * 256 * 256 * 256)
            height = data(22) + (data(23) * 256) + (data(24) * 256 * 256) + (data(25) * 256 * 256 * 256)
            Console.WriteLine("Width: {0} - Heigth: {1}", width, height)
        Catch e As Exception
            Console.WriteLine("Error: {0}!!!", e.message())
        End Try
    End Sub
End Class