Contributions on Lineogrammer

There are two parts in this master's project report. Part 1 describes the features implemented in Lineogrammer paper submitted in April 2008. Part 2 introduces the features implemented since then. Initially, the underlying geometrical structure of the lineogrammer only has lines. In order to manipulate polygons more conveniently, the need to recognize polygons becomes essential. Once a polygon is recognized, it will be filled with the color according to its type of symmetry. Figure 1.1: Polygons with colors that correspond to their types of symmetry We use three types of symmetry: horizontal, vertical and rotational to determine the default color of a polygon. Polygons that contain all three symmetries are color coded light blue. In Figure 1.1, the circle positioned on the top left hand corner fits this description. The parallelogram on the right hand side of the circle is rotationally symmetrical and therefore is coded by the color yellow. The bottom row of figure 1.1 contains two triangles, one with a vertical symmetry and one with a horizontal symmetry. The one with vertical symmetry is color coded pink whereas the one with horizontal symmetry is color coded green. Shapes like the quadrilateral on the bottom left hand corner of figure 1.1 that contains no symmetry whatsoever are assigned the color gray. The line segments above the quadrilateral do not form a cycle and, therefore, they will not be recognized as a polygon. Scribbling on to, therefore deleting any segments from a polygon will result in the incompleteness of a cycle. Since an acyclic shape is not recognized as a polygon, the modifying options that polygons allow are not applicable. Basically, the polygon recognizer is trying to check whether there is a cycle generated after each line stroke or not. If this is the case, a polygon will be created in the underlying geometrical structure of lineogrammer and, according to its type of symmetry, a corresponding color will fill in its fill-area. However, if no cyle is generated, nothing will occur. After a polygon is recognized, it is easy to tell whether the stylus is located inside or outside the polygon. Since the fill area of a polygon presents a relatively large surface area for the stylus to tap, tapping the fill area is perhaps one of the easier methods of selecting. Re-tapping a selected polygon will deselect it. In situations where there are multiple objects, such as other