I think, that there is a "black hole" in tracing tools. None of them (as I know) supports gradient fills. Why so? It is not such a great problem. Moreover, nice looking vectors may be produced using only a pen. Yeah, gradient fills could be realized by an appropriate pen. One needs only draw contour lines, painting is going simultaneously. On the other hand, it means that such kind of vectors could be created from raster objects, using an appropriate tracing tool. This tracer has to detect edges between differently colored regions, convert these contours to vectors and register one non-constant parameter, distributed along these contours. That's all. Vector object, created by this technology, will content only contours, what really present in the source raster. No additional contours. Moreover, there is no need to enclose each region to be painted. Contours may be open arcs as well. If someone has an interest in such technology, visit http://www.smartfills.com . Grayscales at gallery are created with this method. Download PaintingPen and try to convert some raster by yourself (or create a new one). PaintindPenDemo is an imitator, it demonstrates what happens if someone draw lines using PaintingPen