Generating pencil drawings and oil paintings using anisotropic filters

We present a non-photorealistic rendering (NPR) method for generating pencil drawings and oil paintings from photographs. Strokes were generated using anisotropic smoothing filters (ASF). These filters were preliminarily reviewed and extended to NPR methods. In an NPR method for pencil drawings, the original photograph was transformed into a stippled image, which was then filtered by ASFs. Orientation of strokes was aligned with a gradient in luminance or with that of depth values. Cross-hatching type drawings and colored pencil drawings were also presented. In an NPR for oil paintings, random noises were added to the original photograph, which was then filtered by the ASF. Spatial weights in the filter were extended to bandpass characteristics for enhancing strokes. Two types of oil paintings were given. The first one used the gradient of the original photograph and another one used the gradient of the photograph after noise addition.