Abstract: Apparatus that smoothes the discontinuities between serial parallel straight line segments by adding auxiliary dots of lesser diameter below the larger main dots forming a first line segment in a given row and adding the same size auxiliary dots above the main dots of an adjacent line segment when the latter are in a row below the given row. Should the adjacent line segment be above the given row, auxiliary dots are formed below it, some of the auxiliary dots previously formed below the end portion of the first line segment are erased, and auxiliary dots are placed above the main dots for the end portion of the first line segment so as to smooth the discontinuity. In the latter situation, smaller auxiliary dots are preferably placed above and below the central portion of the main dots for the first line segment. More than three different sized dots can be used.