John; "MAKE SURE YOU HAVE A SAVED COPY OF YOUR FILE THAT YOU WILL NOT TOUCH"
Open the image. When the image is on screen, blow the image up to where the pen fills the full screen. Select the tool that looks like a pair of scissors. It is the "Scissors Select Tool". Now click on the edge of the pen. Release the mouse button and move the mouse cursor down the pen. Do this until you have "outlined" the pen entirely. If a line doesn't get draw where you want it, click down on the mouse and drag any line portion to where it should be. Now press <ENTER> to set the selection to the pen. On the menu bar, click on "Select", and "Invert". The selects the background (ie non-pen part of the image). Now click on the "Bucket Flood Fill" tool it looks like a spilling pain can. Make sure the foreground color is black. Position the mouse cursor anywhere on the background and click the mouse. It will take a few seconds to change the background.
You may have to try this several times to get the actions down pat. If you don't succeed the first time, close the image without saving the changes you made and try again.
This is easy to do and difficult to describe.
