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How to Capture and Save a screenshot using a keyboard hook.
Hi, im trying to figure out how I can go about taking, and saving a screenshot using VB.NET, I already have a keyboard hook in place so no matter what when you press the Prt Scr button it fires off an event in the program. the only problem now is how would I go about taking the screenshot then saving it to a file?
thanks in advance.
thanks in advance.
Visual Basic.NET
Last Comment
Bob Learned
ASKER
im using visual studio 2008, but what would be the best way to capture the screenshot from the clipboard and save it directly to a file?
If Clipboard.ContainsImage() Then
Dim img As Image = Clipboard.GetImage()
img.Save(fileName, ImageFormat.Png)
End If
Bob
Dim img As Image = Clipboard.GetImage()
img.Save(fileName, ImageFormat.Png)
End If
Bob
ASKER
wow, thats a lot easier than what I thought, thanks....
only 1 problem is that it seems the keyboard hook im using(which is one I found on here) doesnt let prt scr actually capture the screenshot, so is there a way to get it to capture the screenshot first using vb?
only 1 problem is that it seems the keyboard hook im using(which is one I found on here) doesnt let prt scr actually capture the screenshot, so is there a way to get it to capture the screenshot first using vb?
You might want to look at PreFilterMessage:
IMessageFilter.PreFilterMe
http://msdn2.microsoft.com/en-us/library/system.windows.forms.imessagefilter.prefiltermessage(VS.80).aspx
7.5 How can I catch keyboard messages on a application-wide basis?
http://www.syncfusion.com/FAQ/WindowsForms/FAQ_c46c.aspx
Bob
IMessageFilter.PreFilterMe
http://msdn2.microsoft.com/en-us/library/system.windows.forms.imessagefilter.prefiltermessage(VS.80).aspx
7.5 How can I catch keyboard messages on a application-wide basis?
http://www.syncfusion.com/FAQ/WindowsForms/FAQ_c46c.aspx
Bob
ASKER
hey,
thanks again, but I cant seem to get it to work, here is the code I have right now, basically just copied a keyboard hook that I found on here, how would I implement PreFilterMessage so it lets print screen do its stuff, then fires the event in the application. I have never used PreFilterMessage before.
Thanks again.
thanks again, but I cant seem to get it to work, here is the code I have right now, basically just copied a keyboard hook that I found on here, how would I implement PreFilterMessage so it lets print screen do its stuff, then fires the event in the application. I have never used PreFilterMessage before.
Thanks again.
Imports System.Runtime.InteropServices
Public Class Form1
Dim i As Integer
Private WithEvents llkb As LowLevelKeyBoardhook
Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
llkb = New LowLevelKeyBoardhook
End Sub
Private Sub llkb_PrtScr() Handles llkb.PrtScr
If Clipboard.ContainsImage Then
Dim img As Image = Clipboard.GetImage
img.Save("C:\img001.png")
End If
End Sub
Private Class LowLevelKeyBoardhook
Private Const HC_ACTION As Integer = 0
Private Const WH_KEYBOARD_LL As Integer = 13
Private Const WM_KEYDOWN As Integer = &H100
Private Const WM_SYSKEYDOWN As Integer = &H104
Public Structure KBDLLHOOKSTRUCT
Public vkCode As Integer
Public scancode As Integer
Public flags As Integer
Public time As Integer
Public dwExtraInfo As Integer
End Structure
Private Declare Function SetWindowsHookEx Lib "user32" _
Alias "SetWindowsHookExA" ( _
ByVal idHook As Integer, _
ByVal lpfn As LowLevelKeyboardProcDelegate, _
ByVal hmod As Integer, _
ByVal dwThreadId As Integer) As Integer
Private Declare Function CallNextHookEx Lib "user32" ( _
ByVal hHook As Integer, _
ByVal nCode As Integer, _
ByVal wParam As Integer, _
ByVal lParam As KBDLLHOOKSTRUCT) As Integer
Private Declare Function UnhookWindowsHookEx Lib "user32" ( _
ByVal hHook As Integer) As Integer
Private Delegate Function LowLevelKeyboardProcDelegate( _
ByVal nCode As Integer, _
ByVal wParam As Integer, _
ByRef lParam As KBDLLHOOKSTRUCT) As Integer
Public Event PrtScr()
Private hhkLowLevelKeyboard As Integer
Private keyboardDelegate As LowLevelKeyboardProcDelegate
Public Sub New()
keyboardDelegate = New LowLevelKeyboardProcDelegate(AddressOf Me.LowLevelKeyboardProc)
hhkLowLevelKeyboard = SetWindowsHookEx(WH_KEYBOARD_LL, keyboardDelegate, _
Marshal.GetHINSTANCE(System.Reflection.Assembly.GetExecutingAssembly.GetModules()(0)).ToInt32, 0)
End Sub
Private Function LowLevelKeyboardProc( _
ByVal nCode As Integer, _
ByVal wParam As Integer, _
ByRef lParam As KBDLLHOOKSTRUCT) As Integer
If (nCode = HC_ACTION) Then
Select Case wParam
Case WM_KEYDOWN, WM_SYSKEYDOWN
If lParam.vkCode = Keys.PrintScreen Then
RaiseEvent PrtScr()
End If
End Select
End If
Return CallNextHookEx(hhkLowLevelKeyboard, nCode, wParam, lParam)
End Function
Protected Overrides Sub Finalize()
UnhookWindowsHookEx(hhkLowLevelKeyboard)
MyBase.Finalize()
End Sub
End Class
End Class
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Bob