Other gimp tricks at http://www.instructables.com/id/Enhancing-female-photos/.
Update: I changed the intent of the instructable. (removed a few steps for other content.)
Step 1: Typical instructable photo
Step 2: Get the Gimp
Step 4: Do it to it and your done.
Note: you can only see the difference if you have a failing monitor. Updated picture with newer monitor.
Step 5: Fixing schematics
Open up the picture with the Gimp. Go to "Colors" menu and then click on "Value invert". That is it, except for saving the picture.
Step 6: Removing the squares.
You may have to convert it to gray scale first.