Watercolour Robotic Painting: a Novel Automatic System for Artistic Rendering

Non-Photorealistic Rendering Techniques for Artistic Robotic Painting

“…The image processing algorithms, i.e., the non-photorealistic rendering techniques, are applied to a digital input image that is processed in order to extract the contours, the details and the backgrounds that have to be reproduced on paper. Several different algorithms have been developed for Busker Robot [1,2]: it is the artists responsibility to choose which technique, or combination of techniques, has to be applied case by case. The output of the artistic rendering is a structured list of points that identify the processed image.…”

“…Similarly to [1], the algorithms here presented are based on a thresholding process that is applied to a grey-scale version of the original image. For a given threshold I T , i.e., the value of a specific grey intensity level (between 0 and 1), each pixel of the original image with intensity I(P i ), is transformed into white if I(P i ) ≥ I T , or into black, otherwise.…”

“…The paths resulting from the algorithms are then overlapped to obtain the final result. The NPR algorithms can be used for the processing of the areas with uniform grey intensity level of an image; furthermore, contours and details can also be added to the final result by adopting other techniques such as Canny Edge Detector, Hough Transform or Difference of Gaussians [1,2,32]. The Canny Edge Detector algorithm has been adopted in this work.…”

“…Busker Robot, which name refers to street artists, has been previously presented in [1,2] and has been showcased for the first time in 2016 at the exhibition "Art, Science, Technology, Robotics" in Trieste, Italy. Then, it was shown at the SPS IPC Drives Italy 2017, at the "Algorithmic Arts and Robotics" exhibition during the international event Trieste Next 2017, at "Piccolo Teatro" in Milan, 2017, and, more recently, at the international festival "Robotics" in Trieste, 2018 ( Figure 1) [3].…”

“…Furthermore, it took part to the 2018 International Robotic Art Competition (RobotArt), a context where 19 teams from all over the world competed and more than 100 artworks were created by painting robots; Busker Robot won an Honorable Mention [4]. With respect to previously published works [1,2], in this paper: (a) we present two novel non-photorealistic rendering techniques, cross-hatching and Random Splines, which are adopted for the artistic rendering of light and shades on an image, and (b) we employ non-diluted black Indian ink, instead of the previously adopted watercolor and gouache techniques.…”