User blog comment:CitizenA/Paint.NET silhouette plugin/@comment-7927437-20130410151332/@comment-5153132-20130411204210

One thing that MIGHT be a problem is the color scheme of the original image. If you look at Thomas' images they have a bug that part disapear because they are black.

Else try taking a look at the marco's travels (1) sidestory. It seem that that story does what you want so you could take a look and see if you see any differences.