You probably just need to change its settings, especially the Dark-White slider.

The Picture Stencil Maker won't be able to give a great result with every image. You can try its different settings. If none work well enough, you can u...

The Vectorizer is for when you need to convert an image to a vector file: SVG, DXF, etc. If you don't need that, stick to the Picture Stencil tool.