Here's some code I use to copy part of a bitmap image to the ClipRectangle
passed for repainting.  Note that v_BackImage is my background bitmap I
defined as a private variable in my overall class.

  Private Sub me_Paint(ByVal sender As Object, ByVal e As
System.Windows.Forms.PaintEventArgs) Handles MyBase.Paint
       Dim hdcControl As IntPtr = e.Graphics.GetHdc
       Dim hdcBitmapDC As IntPtr = gph.GetHdc
       Dim hdcBitmapHandle As IntPtr = v_BackImage.GetHbitmap  'This takes
up 85% of time
       SelectObject(hdcBitmapDC, hdcBitmapHandle)
       BitBlt(hdcControl, e.ClipRectangle.X, e.ClipRectangle.Y,
e.ClipRectangle.Width, e.ClipRectangle.Height, hdcBitmapDC,
e.ClipRectangle.X, e.ClipRectangle.Y, &HCC0020)
       DeleteObject(hdcBitmapHandle)
       gph.ReleaseHdc(hdcBitmapDC)
       e.Graphics.ReleaseHdc(hdcControl)
exit sub

       '**** Explaination of above *********
       ' BitBlt copies the graphic data to a Device Context. A Device
Context is a data structure maintained by GDI. A device context is
       'associated with a particular display device, such as a printer or
video display. For a video display, a device context is usually
       'associated with a particular window on the display, but it can also
be an offscreen display.

       'What you do, is create a Device Context and then associate a Bitmap
with the Device Context ( with SelectObject ). Then you
       ' draw to the Device Context ( using BitBlt ) to alter the Bitmap.
You can't use GDI functions to directly draw to a bitmap.

       'After using a Device Context, you need to clean stuff up ( release
and delete ) or else the device context stays locked and
       ' other attempts to draw again will fail. Also not cleaning up will
result in memory leaks.