Como copiar a tela do Windows via código em delphi

procedure PrintScreen(Image: TBitmap);
var
DC: HDC;
begin
DC:= GetDC(GetDesktopWindow);
try
Image.Width:= GetDeviceCaps(DC, HorzRes);
Image.Height:= GetDeviceCaps(DC, VertRes);
BitBlt(Image.Canvas.Handle, 0, 0, Image.Width, Image.Height, DC, 0, 0, SRCCOPY);
finally
ReleaseDC(GetDesktopWindow, DC);
end;
end;
Utilize o procedimento assim:
begin
Image1.Picture:= nil;
PrintScreen(Image1.Picture.Bitmap);
end;