Constrained 2D sketch generation based on image contour detect

We proposed a method to auto-extract contour sketch from color image. Firstly, we get binary image through OTSU method, and then trace the contour of the binary image. Secondly, map the contour to the specified sketch plane. We use Hough Transform to detect all possible line segments in the contour, use Randomized Circle Detection algorithm to get all possible circular arcs, and then determine the break points of the contour according to the constraints between the fitted line segments and circular arcs. Finally, we refit the curve set by the global constraint formula based on the estimated curve type and constraints. Examples show that the method can recognize the curve type and corresponding constraints accurately, and can extract contour sketch from the color image as expected.