Taking screenshot of a particular component of a frame

[chinmayzen]

hi,

i am making a small application where i need to take a screenshot of a textbox. i am learning vb and i found in one of the books keybd_event to simulate a screenshot..

keybd_event 44, 1, 0, 0
Picture1.Image = Clipboard.GetData

keybd_event takes the shot of the entire frame.. (as expected)

does anyone know how to take a screenshot of a particular component of a frame?

another question -- is there any way i can edit an image that is there in the clipboard (or crop an image - for that matter) ??

thanks!

edit: this is my first post here, so please bear with me if i have not followed the ethics here! cheers!

[DigiRev]

Here's a quick example of taking a screenshot of a TextBox control. Just needs a picturebox on the form, and a command button.

You can do the same thing without using a temporary picturebox (by using a DC in memory) but I don't have the time right now.

Option Explicit

Private Declare Function GetDC Lib "user32" (ByVal hwnd As Long) As Long
Private Declare Function BitBlt Lib "gdi32" (ByVal hDestDC As Long, ByVal x As Long, ByVal y As Long, ByVal nWidth As Long, ByVal nHeight As Long, ByVal hSrcDC As Long, ByVal xSrc As Long, ByVal ySrc As Long, ByVal dwRop As Long) As Long

Private Sub Command1_Click()
    
    ScreenshotControl Text1, picTemp, "C:\textbox.bmp"
    
End Sub

Private Sub Form_Load()
    
    Me.ScaleMode = vbPixels
    
End Sub

Private Sub ScreenshotControl(ByRef TheControl As Control, _
    ByRef TempPicture As PictureBox, _
    ByRef SavePath As String)
    
    Dim lonDC As Long
    
    lonDC = GetDC(TheControl.hwnd)
    
    With TempPicture
        .Cls
        .AutoRedraw = True
        .ScaleMode = vbPixels
        .Width = TheControl.Width
        .Height = TheControl.Height
        
        BitBlt .hDC, 0, 0, .ScaleWidth, .ScaleHeight, _
            lonDC, 0, 0, vbSrcCopy
        
        SavePicture TempPicture.Image, SavePath
    End With
    
End Sub

[LaVolpe]

Regarding the textbox. If the textbox is an actual textbox and you know the hWnd, you can get a "snapshot" but you could also get the text itself. But you will need the hWnd of that control either way.

' snapshot example
Private Declare Function PrintWindow Lib "user32.dll" (ByVal hWnd As Long, ByVal hdcBlt As Long, ByVal nFlags As Long) As Long

Private Sub Command1_Click()
    PrintWindow TexthWnd, Picture1.hDC, 0&
    ' supply the hWnd of the textbox control as TexthWnd
End Sub

To get the actual text

Private Declare Function SendMessage Lib "user32.dll" Alias "SendMessageA" (ByVal hwnd As Long, ByVal wMsg As Long, ByVal wParam As Long, ByRef lParam As Any) As Long
Private Const WM_GETTEXTLENGTH As Long = &HE
Private Const WM_GETTEXT As Long = &HD

Private Sub Command1_Click()
    Dim sText As String, lLen As Long
    lLen = SendMessage(TexthWnd, WM_GETTEXTLENGTH, 0&, ByVal 0&)
    If lLen Then
         sText = String$(lLen, vbNullChar)
         SendMessage TexthWnd, WM_GETTEXT, lLen + 1, ByVal sText
         Picture1.Print sText
    End If
    ' supply the hWnd of the textbox control as TexthWnd
End Sub

There are other methods of getting a "window capture", as DigiRev has displayed (beat me to the punch)

[chinmayzen]

that was fast! thanks! i'll try this! many many thanks!!

[DigiRev]

I never knew there was a PrintWindow API function. That way seems a lot easier.

[LaVolpe]

I never knew there was a PrintWindow API function. That way seems a lot easier.

PrintWindow. XP and above per MSDN link. Your way is compatible for all O/S.