Saving the Windows Form to image file programmatically

There is an article found here which shows how to programmatically save the Windows Form directly to an image file. The original code is as follows:

Const SRCCOPY As Integer = &HCC0020

Public Declare Function BitBlt Lib "gdi32" ( _
ByVal hDestDC As IntPtr, _
ByVal x As Integer, _
ByVal y As Integer, _
ByVal nWidth As Integer, _
ByVal nHeight As Integer, _
ByVal hSrcDC As IntPtr, _
ByVal xSrc As Integer, _
ByVal ySrc As Integer, _
ByVal dwRop As Integer _
) As Integer

'================================================= ==================
Public Function CaptureControl(ByVal c As Control) As Bitmap

Dim bmp As Bitmap
Dim gDest, gSource As Graphics
Dim hdcSource, hdcDest As IntPtr

bmp = New Bitmap(c.Width, c.Height)

gSource = c.CreateGraphics
Try
gDest = Graphics.FromImage(bmp)
Try
hdcSource = gSource.GetHdc
Try
hdcDest = gDest.GetHdc
Try
BitBlt( _
hdcDest, 0, 0, _
c.Width, c.Height, _
hdcSource, 0, 0, SRCCOPY _
)
Finally
gDest.ReleaseHdc(hdcDest)
End Try
Finally
gSource.ReleaseHdc(hdcSource)
End Try
Finally
gDest.Dispose()
End Try
Finally
gSource.Dispose()
End Try

Return bmp
End Function

However, I had to place an offset in order to get the image to capture correctly.

My revised code is as follows:

Const SRCCOPY As Integer = &HCC0020

    Public Declare Function BitBlt Lib "gdi32" ( _
        ByVal hDestDC As IntPtr, _
        ByVal x As Integer, _
        ByVal y As Integer, _
        ByVal nWidth As Integer, _
        ByVal nHeight As Integer, _
        ByVal hSrcDC As IntPtr, _
        ByVal xSrc As Integer, _
        ByVal ySrc As Integer, _
        ByVal dwRop As Integer _
        ) As Integer

    '================================================= ==================
    Public Function CaptureControl(ByVal c As Control) As Bitmap

        Dim bmp As Bitmap
        Dim gDest, gSource As Graphics
        Dim hdcSource, hdcDest As IntPtr

        bmp = New Bitmap(c.Width, c.Height)

        gSource = c.CreateGraphics
        Try
            gDest = Graphics.FromImage(bmp)
            Try
                hdcSource = gSource.GetHdc
                Try
                    hdcDest = gDest.GetHdc
                    Try
                        BitBlt( _
                        hdcDest, 0, 0, _
                        c.Width, c.Height, _
                        hdcSource, -3, -27, SRCCOPY _
                        )
                    Finally
                        gDest.ReleaseHdc(hdcDest)
                    End Try
                Finally
                    gSource.ReleaseHdc(hdcSource)
                End Try
            Finally
                gDest.Dispose()
            End Try
        Finally
            gSource.Dispose()
        End Try

        Return bmp
    End Function

To use the code:

    Private Sub btnSave_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnSave.Click

        Dim x As Bitmap
        Me.Activate()
        x = CaptureControl(Me)
        x.Save("c:\t2.bmp", Imaging.ImageFormat.Bmp)

    End Sub