Hola, para aportar un poco, como te decian antes utilizando GDI, solo que no usaria BitBlt, o StretchBlt ya que estas no funcionarían si la ventana no esta visible osea detrás de otra, si esta minimizada no hay solución, si o si tienes que restaurarla como ya dijo x64Core (ShowWindow), entonces volviendo a la api para capturar la ventana te recomiendo PrintWindow
Private Declare Function PrintWindow Lib "user32.dll" (ByVal hWnd As Long, ByVal hdcBlt As Long, ByVal nFlags As Long) As Long
para poder utilizarla tienes que tener el hwnd de la ventana lo puedes hacer con FindWindow (simpre y cuando esa ventana tenga un caption fijo)
el segundo parametro de la api es el hdc donde quieres dibujarlo por ejemplo, si la quieres hacer facil utiliza un picturebox. y el tercer parametro con 0 esta bien.
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Me tome un tiempo y te prepare algo que va a ser mejor que explicártelo.
en un formulario pone este código y un command1 (osea un boton)
Option Explicit
Private Declare Function FindWindow Lib "user32.dll" Alias "FindWindowA" (ByVal lpClassName As String, ByVal lpWindowName As String) As Long
Private Declare Function GetWindowRect Lib "user32.dll" (ByVal hWnd As Long, ByRef lpRect As RECT) As Long
Private Declare Function CreateCompatibleDC Lib "gdi32.dll" (ByVal hdc As Long) As Long
Private Declare Function SelectObject Lib "gdi32.dll" (ByVal hdc As Long, ByVal hObject As Long) As Long
Private Declare Function ReleaseDC Lib "user32.dll" (ByVal hWnd As Long, ByVal hdc As Long) As Long
Private Declare Function DeleteObject Lib "gdi32.dll" (ByVal hObject As Long) As Long
Private Declare Function IsIconic Lib "user32.dll" (ByVal hWnd As Long) As Long
Private Declare Function ShowWindow Lib "user32.dll" (ByVal hWnd As Long, ByVal nCmdShow As Long) As Long
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 Declare Function UpdateWindow Lib "user32.dll" (ByVal hWnd As Long) As Long
Private Declare Function GetDC Lib "user32.dll" (ByVal hWnd As Long) As Long
Private Declare Function CreateCompatibleBitmap Lib "gdi32.dll" (ByVal hdc As Long, ByVal nWidth As Long, ByVal nHeight As Long) As Long
Private Declare Function PrintWindow Lib "user32.dll" (ByVal hWnd As Long, ByVal hdcBlt As Long, ByVal nFlags As Long) As Long
Private Declare Function DeleteDC Lib "gdi32.dll" (ByVal hdc As Long) As Long
Private Const WM_SYSCOMMAND As Long = &H112
Private Const SC_RESTORE As Long = &HF120&
Private Type RECT
Left As Long
Top As Long
Right As Long
Bottom As Long
End Type
Private Type GDIPlusStartupInput
GdiPlusVersion As Long
DebugEventCallback As Long
SuppressBackgroundThread As Long
SuppressExternalCodecs As Long
End Type
Private Type GUID
Data1 As Long
Data2 As Integer
Data3 As Integer
Data4(0 To 7) As Byte
End Type
Private Type EncoderParameter
GUID As GUID
NumberOfValues As Long
Type As Long
Value As Long
End Type
Private Type EncoderParameters
Count As Long
Parameter(15) As EncoderParameter
End Type
Private Const ImageCodecJPG = "{557CF401-1A04-11D3-9A73-0000F81EF32E}"
Private Const EncoderQuality = "{1D5BE4B5-FA4A-452D-9CDD-5DB35105E7EB}"
Private Declare Function GdiplusStartup Lib "gdiplus" (Token As Long, inputbuf As GDIPlusStartupInput, Optional ByVal outputbuf As Long = 0) As Long
Private Declare Sub GdiplusShutdown Lib "gdiplus" (ByVal Token As Long)
Private Declare Function GdipCreateBitmapFromHBITMAP Lib "GdiPlus.dll" (ByVal mHbm As Long, ByVal mhPal As Long, ByRef mBitmap As Long) As Long
Private Declare Function GdipSaveImageToFile Lib "gdiplus" (ByVal image As Long, ByVal FileName As Long, ByRef clsidEncoder As GUID, ByRef encoderParams As Any) As Long
Private Declare Function GdipDisposeImage Lib "gdiplus" (ByVal image As Long) As Long
Private Declare Function CLSIDFromString Lib "ole32" (ByVal str As Long, Id As GUID) As Long
Private Sub Form_Load()
Shell "calc.exe" 'esto es solo un ejemplo
End Sub
Private Sub Command1_Click()
Dim hWnd As Long
Dim DestPath As String
DestPath = "C:\Captura1.jpg" 'Destino donde se guardara la imagen
hWnd = FindWindow(vbNullString, "Calculadora") ' handle de la ventana mediante su caption.
If (hWnd <> 0) And (LenB(DestPath) > 0) Then
If CaptureWindow(hWnd, DestPath) Then ' funcion para capturar y guardar la ventana como una imagen.jpg
Me.Picture = LoadPicture(DestPath) ' leemos la image para mostrar el resultado.
End If
End If
End Sub
Private Function CaptureWindow(hWnd As Long, ByVal DestPath As String) As Boolean
Dim tRECT As RECT
Dim lWidth As Long, lHeight As Long
Dim DC As Long
Dim hDCMemory As Long
Dim hBmp As Long
Dim OldhBmp As Long
'Si la ventana esta minimizada la restaura
If IsIconic(hWnd) Then
SendMessage hWnd, WM_SYSCOMMAND, SC_RESTORE, ByVal 0&
DoEvents
End If
'le peta una refrescada
UpdateWindow hWnd
'obtiene las medidas
GetWindowRect hWnd, tRECT
lWidth = tRECT.Right - tRECT.Left
lHeight = tRECT.Bottom - tRECT.Top
'creamos un bitmap y un hdc
DC = GetDC(hWnd)
hDCMemory = CreateCompatibleDC(0)
hBmp = CreateCompatibleBitmap(DC, lWidth, lHeight)
SelectObject hDCMemory, hBmp
ReleaseDC hWnd, hdc
'imprimimos la ventana en el hdc
PrintWindow hWnd, hDCMemory, 0
'---------- Rutina para guardar el bmp como un jpg mediante GDI Plus
Dim gToken As Long
Dim gdiSI As GDIPlusStartupInput
Dim hImage As Long
Dim tEncoder As GUID
Dim tParams As EncoderParameters
Dim JPG_Quality As Long
JPG_Quality = 80
gdiSI.GdiPlusVersion = &H1
GdiplusStartup gToken, gdiSI
If gToken Then
If GdipCreateBitmapFromHBITMAP(hBmp, 0&, hImage) = 0 Then
CLSIDFromString StrPtr(ImageCodecJPG), tEncoder
With tParams
.Count = 1
.Parameter(0).NumberOfValues = 1&
.Parameter(0).Type = 4&
.Parameter(0).Value = VarPtr(JPG_Quality)
CLSIDFromString StrPtr(EncoderQuality), .Parameter(0).GUID
End With
If GdipSaveImageToFile(hImage, StrPtr(DestPath), tEncoder, ByVal tParams) = 0 Then
CaptureWindow = True
End If
GdipDisposeImage hImage
End If
GdiplusShutdown gToken
End If
'-----------
'Liberamos los objetos GDI
DeleteObject SelectObject(hDCMemory, OldhBmp)
DeleteDC hDCMemory
End Function
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