"Shin-hanga" Filter with Improved Contour Lines and Gradation

The filter simulates "Shinhanga," multi-colored woodblock print, which was once popular in Japan around one hundred years ago. We expect that the filter sheds light again on this fascinating art style. The filter follows three steps to simulate contour lines and gradation, which characterize "Shinhanga"; The filter extracts contour lines based on hue of an original image, then determines the direction of color gradient in each region either vertically or horizontally, based on the amount and the direction of variation of hue in each region. We improved the contour lines and gradation process from the previous filter to broaden its applicability and conducted an experiment to assess it. The result suggests that the filter has less dependency to the types of images comparing to our previously proposed method.