There are a few things that you can do, but none are to read in the image file into GibbsCAM. It would be very nice though.
I have several customers using a program called scan2cad. This seems to work very well. It is designed specificly for manufacturing and design. You can convert images and scaned drawings to DXF files.
There are a few different options but they start at (or are around) $275 - $300 range.
Check them out at
www.softcover.com
As for WinTopo, I tried it and did not have the best of luck, even though it did work.
GG