We are studying non-photo realistic rendering (NPR) with the goal of developing an image expression tool to create artworks by the NPR technique. The purpose of most NPR researches is to simulate typical painting styles, so they focus on techniques to create brushstrokes. These superficially modified images cannot deviate far from the source photo. If a rendered image is seen from a distance, it is difficult to tell the difference from the source photo. This fact makes us realize that other important elements to add artistic expression to the photographs exist. We supposed that the distribution of bright and dark parts over the painting is essential and proposed the effective way to modify that. Our novel technique is based on knowledge about human optical illusions and basic visual design rules. We integrate this technique into our NPR system, which was used to make the artworks selected by SIGGRAPH 2002 2D art gallery.

Furthermore, we present new features that allow artist to select appropriate area for extreme expressions, to create many types of brushstrokes, and to choose more than two types of brushstrokes for a single artwork.