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How do I capture a bitmap of my form

Platform: WinForms| Category: Bitmaps and Images

You can import the BitBlt API to handle this problem. Here is a solution offered by Simon Murrell and Lion Shi in the microsoft.public.dotnet.windows.forms newsgroup. The number used below, 13369376, is Int32 SRCCOPY = 0xCC0020;


You can use Gdi32 dll. You can define the BitBlt method found within the Gdi32 dll with the code below.

[System.Runtime.InteropServices.DllImportAttribute('gdi32.dll')]
private static extern bool BitBlt(
	ntPtr hdcDest, // handle to destination DC
	int nXDest,  // x-coord of destination upper-left corner
	int nYDest,  // y-coord of destination upper-left corner
	int nWidth,  // width of destination rectangle
	int nHeight, // height of destination rectangle
	IntPtr hdcSrc,  // handle to source DC
	int nXSrc,   // x-coordinate of source upper-left corner
  	int nYSrc,   // y-coordinate of source upper-left corner
	System.Int32 dwRop  // raster operation code
);

And you can then use the copy below in a button click event to save the form to an image.

	Graphics g1 = this.CreateGraphics();
	Image MyImage = new Bitmap(this.ClientRectangle.Width, this.ClientRectangle.Height, g1);
	Graphics g2 = Graphics.FromImage(MyImage);
	IntPtr dc1 = g1.GetHdc();
	IntPtr dc2 = g2.GetHdc();
	BitBlt(dc2, 0, 0, this.ClientRectangle.Width, this.ClientRectangle.Height, dc1, 0, 0, 13369376);
	g1.ReleaseHdc(dc1);
	g2.ReleaseHdc(dc2);
	MyImage.Save(@'c:\Captured.bmp', ImageFormat.Bmp);

You will need to use the System.Drawing.Imaging namespace.

Here is VB code posted by Armin Zingler in the microsoft.public.dotnet.languages.vb newsgroup.


Public Class Win32

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


	Public Declare Function GetWindowDC Lib 'user32' Alias 'GetWindowDC' _
		(ByVal hwnd As Integer) As Integer

	Public Declare Function ReleaseDC Lib 'user32' Alias 'ReleaseDC' _
		(ByVal hwnd As Integer, ByVal hdc As Integer) As Integer

	Public Const SRCCOPY As Integer = &HCC0020

End Class

Public Class Hardcopy

	Public Shared Function CreateBitmap( _
			ByVal Control As Control) _
			 As Bitmap

		Dim gDest As Graphics
		Dim hdcDest As IntPtr
		Dim hdcSrc As Integer
		Dim hWnd As Integer = Control.Handle.ToInt32

		CreateBitmap = New Bitmap(Control.Width, Control.Height)
		gDest = gDest.FromImage(CreateBitmap)

		hdcSrc = Win32.GetWindowDC(hWnd)
		hdcDest = gDest.GetHdc

		Win32.BitBlt( _
			hdcDest.ToInt32, 0, 0, Control.Width, Control.Height, _
 			hdcSrc, 0, 0, Win32.SRCCOPY _
			 )

 		gDest.ReleaseHdc(hdcDest)
	 	Win32.ReleaseDC(hWnd, hdcSrc)

	End Function

End Class

’In your Form:

Private Sub Button1_Click( _
		ByVal sender As System.Object, _
		ByVal e As System.EventArgs) _
		Handles Button1.Click

	Dim bmp As Bitmap

	bmp = Hardcopy.CreateBitmap(Me)
	bmp.Save('c:\test.bmp')

End Sub

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