Real-time Coloring to Freehand Line Drawings in Online

Abstract

We present a method for real-time coloring to freehand line drawings in parallel with being drawn on a tablet in online. The proposed method is based on our previous one for coloring to freehand drawings so that it allows general users including beginners to complete art-like works in a short time. For freehand lines that a user draws onto a photograph as a reference image, coloring is accomplished by a Delaunay triangulation for the set of sampling points on the drawn lines, sampling of color in each triangle on the reference image, smoothing of color among neighboring triangles, and painting of each triangle with the smoothed color. In real-time coloring, the coloring result is displayed and updated every time a freehand stroke is added to the drawings.