  In this paper, we propose dualFace, a portrait drawing interface to assist
users with different levels of drawing skills to complete recognizable and
authentic face sketches. dualFace consists of two-stage drawing assistance to
provide global and local visual guidance: global guidance, which helps users
draw contour lines of portraits (i.e., geometric structure), and local
guidance, which helps users draws details of facial parts (which conform to
user-drawn contour lines), inspired by traditional artist workflows in portrait
drawing. In the stage of global guidance, the user draws several contour lines,
and dualFace then searches several relevant images from an internal database
and displays the suggested face contour lines over the background of the
canvas. In the stage of local guidance, we synthesize detailed portrait images
with a deep generative model from user-drawn contour lines, but use the
synthesized results as detailed drawing guidance. We conducted a user study to
verify the effectiveness of dualFace, and we confirmed that dualFace
significantly helps achieve a detailed portrait sketch. see
http://www.jaist.ac.jp/~xie/dualface.html
