In digital illustration, there exist painting styles that combine multiple visual effects specific to painting materials. While these styles offer a wide range of artistic expressions and make illustrations more fascinating, they require artistic expertise in terms of how to apply and harmonize the effects of each painting material. In this study, we define these painting styles as Mixed Painting Material Style, and present an NPR framework to retouch an input image to the style. The framework partitions the input image into multiple regions, and converts the regions with high saliency to oil painting and the regions with low saliency to watercolor. This article also includes a few application examples to verify the effect of the present NPR framework.

input(left), output(right)


NameAffiliationWeb site
Tomoya KobayashiKeio University




  1. Tomoya Kobayashi, Issei Fujishiro: “Photo retouching for mixed painting material style in digital illustrations with verification of its visual effects,” in Proceedings of Expressive Japan 2022 (The Institute of Image Information and Television Engineers Technical Report, Vol. 46, No. 10), AIT2022-61 (pp. 91–94), online, March 8, 2022 (in Japanese).
  2. Tomoya KobayashiIssei Fujishiro: “Photo retouching for mixed painting material style in digital illustrations,” in Proceedings of the 84th National Convention of International Processing Society of Japan, Vol. 4, pp. 345―346 (6ZG-03), Ehime University, Online & Onsite Hybrid, March 5, 2022 (in Japanese).


  1. Grant-in-Aid for Challenging Research (Pioneering): 20K20481 (2021―2022)

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