Grazie per la risposta. Ho apportato delle altre modifiche al codice perché continuava a dare errori e alla fine sono riuscito a farla funzionare! posto l'intera classe nel caso possa essere d'aiuto ad altri:
Inserire in un file di classe nel progetto il seguente codice:
codice:
Imports System
Imports System.Runtime.InteropServices
Imports System.Drawing
Imports System.Drawing.Imaging
Namespace ScreenShotDemo
_
'/ <summary>
'/ Provides functions to capture the entire screen, or a particular window, and save it to a file.
'/ </summary>
Public Class ScreenCapture
'/ <summary>
'/ Creates an Image object containing a screen shot of the entire desktop
'/ </summary>
'/ <returns></returns>
Public Function CaptureScreen() As Image
Return CaptureWindow(User32.GetDesktopWindow())
End Function 'CaptureScreen
'/ <summary>
'/ Creates an Image object containing a screen shot of a specific window
'/ </summary>
'/ <param name="handle">The handle to the window. (In windows forms, this is obtained by the Handle property)</param>
'/ <returns></returns>
Public Function CaptureWindow(ByVal handle As IntPtr) As Image
' get te hDC of the target window
Dim hdcSrc As IntPtr = User32.GetWindowDC(handle)
' get the size
Dim windowRect As New User32.RECT()
User32.GetWindowRect(handle, windowRect)
Dim width As Integer = windowRect.right - windowRect.left
Dim height As Integer = windowRect.bottom - windowRect.top
' create a device context we can copy to
Dim hdcDest As IntPtr = GDI32.CreateCompatibleDC(hdcSrc)
' create a bitmap we can copy it to,
' using GetDeviceCaps to get the width/height
Dim hBitmap As IntPtr = GDI32.CreateCompatibleBitmap(hdcSrc, width, height)
' select the bitmap object
Dim hOld As IntPtr = GDI32.SelectObject(hdcDest, hBitmap)
' bitblt over
GDI32.BitBlt(hdcDest, 0, 0, width, height, hdcSrc, 0, 0, GDI32.SRCCOPY)
' restore selection
GDI32.SelectObject(hdcDest, hOld)
' clean up
GDI32.DeleteDC(hdcDest)
User32.ReleaseDC(handle, hdcSrc)
' get a .NET image object for it
Dim img As Image = Image.FromHbitmap(hBitmap)
' free up the Bitmap object
GDI32.DeleteObject(hBitmap)
Return img
End Function 'CaptureWindow
'/ <summary>
'/ Captures a screen shot of a specific window, and saves it to a file
'/ </summary>
'/ <param name="handle"></param>
'/ <param name="filename"></param>
'/ <param name="format"></param>
Public Sub CaptureWindowToFile(ByVal handle As IntPtr, ByVal filename As String, ByVal format As ImageFormat)
Dim img As Image = CaptureWindow(handle)
img.Save(filename, format)
End Sub 'CaptureWindowToFile
'/ <summary>
'/ Captures a screen shot of the entire desktop, and saves it to a file
'/ </summary>
'/ <param name="filename"></param>
'/ <param name="format"></param>
Public Sub CaptureScreenToFile(ByVal filename As String, ByVal format As ImageFormat)
Dim img As Image = CaptureScreen()
img.Save(filename, format)
End Sub 'CaptureScreenToFile
_
'/ <summary>
'/ Helper class containing Gdi32 API functions
'/ </summary>
Private Class GDI32
Public Shared SRCCOPY As Integer = &HCC0020
' BitBlt dwRop parameter
<DllImport("gdi32.dll")> _
Public Shared Function CreateCompatibleBitmap(ByVal hDC As IntPtr, ByVal nWidth As Integer, ByVal nHeight As Integer) As IntPtr
End Function
<DllImport("gdi32.dll")> _
Public Shared Function BitBlt(ByVal hObject As IntPtr, ByVal nXDest As Integer, ByVal nYDest As Integer, ByVal nWidth As Integer, ByVal nHeight As Integer, ByVal hObjectSource As IntPtr, ByVal nXSrc As Integer, ByVal nYSrc As Integer, ByVal dwRop As Integer) As Boolean
End Function
<DllImport("gdi32.dll")> _
Public Shared Function CreateCompatibleDC(ByVal hDC As IntPtr) As IntPtr
End Function
<DllImport("gdi32.dll")> _
Public Shared Function DeleteDC(ByVal hDC As IntPtr) As Boolean
End Function
<DllImport("gdi32.dll")> _
Public Shared Function DeleteObject(ByVal hObject As IntPtr) As Boolean
End Function
<DllImport("gdi32.dll")> _
Public Shared Function SelectObject(ByVal hDC As IntPtr, ByVal hObject As IntPtr) As IntPtr
End Function
End Class 'GDI32
_
'/ <summary>
'/ Helper class containing User32 API functions
'/ </summary>
Private Class User32
<StructLayout(LayoutKind.Sequential)> _
Public Structure RECT
Public left As Integer
Public top As Integer
Public right As Integer
Public bottom As Integer
End Structure 'RECT
<DllImport("user32.dll")> _
Public Shared Function GetDesktopWindow() As IntPtr
End Function
<DllImport("user32.dll")> _
Public Shared Function GetWindowDC(ByVal hWnd As IntPtr) As IntPtr
End Function
<DllImport("user32.dll")> _
Public Shared Function ReleaseDC(ByVal hWnd As IntPtr, ByVal hDC As IntPtr) As IntPtr
End Function
<DllImport("user32.dll")> _
Public Shared Function GetWindowRect(ByVal hWnd As IntPtr, ByRef rect As RECT) As IntPtr
End Function
End Class 'User32
End Class 'ScreenCapture
End Namespace 'ScreenShotDemo
Un esempio dell'utilizzo della classe è:
codice:
Dim sc As New ScreenCapture()
sc.CaptureScreenToFile("C:\temp2.gif", Imaging.ImageFormat.gif)
Ps. cosa strana è che anche AspAlliance traduce il codice C# della classe originale nel codice Vb.Net che mi dava tanti errori. Sarà che anche la classe in c# abbia errori?
Ciao e grazie tante a MItaly.
(ma penso che si fosse capito :P )
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