How to capture active windows on desktop by vb.net? - vb.net

Question

I'm using this code to capture desktop
Private Function cc() As Bitmap
Dim s As Screen = Screen.PrimaryScreen
Dim img As New Bitmap(s.Bounds.Width, s.Bounds.Height)
Dim gr As Graphics = Graphics.FromImage(img)
gr.CopyFromScreen(s.Bounds.Location, Point.Empty, s.Bounds.Size)
Return img
End Function
Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
Try
Me.PictureBox1.Image = cc()
Catch ex As Exception
MsgBox(ex.Message)
End Try
End Sub
But now I want to capture only the active screen, how can I do that?
Regards,,,,,

Answer 1

for copy active window from our application, Just check the position and size of the window and reduced the copying to this rectangle:
Public Sub ScreenCopy(Optional file As String = "d:\test.jpg")
Dim bounds = Me.Bounds
Using bitmap As New Bitmap(bounds.Width, bounds.Height)
Using g = Graphics.FromImage(bitmap)
g.CopyFromScreen(New Point(bounds.Left, bounds.Top), Point.Empty, bounds.Size)
End Using
bitmap.Save(file, ImageFormat.Jpeg)
Process.Start(file) ' for test purposes
End Using
End Sub
for copy current active window even is not part of our application you need use an api for detect his size and location.
for this use this class (credit: #KvanTTT: https://stackoverflow.com/a/9087955/1271037)
Class ScreenCapturer
<DllImport("user32.dll")> _
Private Shared Function GetForegroundWindow() As IntPtr
End Function
<DllImport("user32.dll")> _
Private Shared Function GetWindowRect(hWnd As IntPtr, ByRef rect As Rect) As IntPtr
End Function
<StructLayout(LayoutKind.Sequential)> _
Private Structure Rect
Public Left As Integer
Public Top As Integer
Public Right As Integer
Public Bottom As Integer
End Structure
Public Function Capture(Optional activeWindowOnly As Boolean = True) As Bitmap
Dim bounds As Rectangle
If Not activeWindowOnly Then
bounds = Screen.GetBounds(Point.Empty)
CursorPosition = Cursor.Position
Else
Dim foregroundWindowsHandle = GetForegroundWindow()
Dim rect = New Rect()
GetWindowRect(foregroundWindowsHandle, rect)
bounds = New Rectangle(rect.Left, rect.Top, rect.Right - rect.Left, rect.Bottom - rect.Top)
CursorPosition = New Point(Cursor.Position.X - rect.Left, Cursor.Position.Y - rect.Top)
End If
Dim result = New Bitmap(bounds.Width, bounds.Height)
Using g = Graphics.FromImage(result)
g.CopyFromScreen(New Point(bounds.Left, bounds.Top), Point.Empty, bounds.Size)
End Using
Return result
End Function
Public Property CursorPosition() As Point
End Class
how to use:
Public Sub ScreenCopy(Optional file As String = "d:\test.jpg")
Dim sc = New ScreenCapturer()
Using bitmap = sc.Capture()
bitmap.Save(file, ImageFormat.Jpeg)
Process.Start(file) ' for test purposes
End Using
End Sub

Answer 2

Only a small change in syntax for VB.net regarding the DLL import:
<DllImport("user32.dll", EntryPoint:="GetForegroundWindow")> Private Shared Function GetForegroundWindow() As IntPtr
End Function
<DllImport("user32.dll", EntryPoint:="GetWindowRect")> Private Shared Function GetWindowRect(hWnd As IntPtr, ByRef rect As Rect) As IntPtr
End Function