Hegron, GerardC.E. Vandoni2015-09-292015-09-2919851017-4656https://doi.org/10.2312/eg.19851022In this report, we propose to present most of the treatments about convex and nonconvex colored shapes from a data structure of their contour which is the general approach of contour tracking . Contour filling and oblique cross-hatching take advantage of the coherence between adjacent scan lines and adjacent hatching lines. The position of a point with respect to a nonconvex polygon is solved from filling logic, and the clipping of a line segment by a nonconvex polygon uses the slant cross-hatching idea. We present the clipping of the two nonconvex polygon set. From the area filling of non polygonal blobs, contour tracking is generalized to three geometric problems : position of a point, clipping of a line segment and of a circular arc by a non-polygonal contour, Finally, we discuss the general advantages of contour tracking and application in the writing of a text in a nonconvex polygon.10.2312/eg.19851022