It is impossible to make an embroidery design (such as .jef files for Janome machines) from a bitmap source (.jpg for example) with just a simple graphics editor. That is because embroidery files are special vector based images that also have special instructions for the stitching machine so it can be sewn on the piece of cloth.
However, an experienced graphics designer might be able to create embroidery design from some image. This is done with usually expensive digitizer software. Some embroidery software can also possess basic digitizing function that can convert raster image to embroidery, but that's usually far from perfect. You just need to look for one that supports Janome formats.
Updated: August 1, 2016