//-------------------------------------------------------calc_polygon_area public static double calc_polygon_area(VertexSequence st) { int i; double sum = 0.0; double x = st[0].x; double y = st[0].y; double xs = x; double ys = y; for (i = 1; i < st.size(); i++) { VertexDistance v = st[i]; sum += x * v.y - y * v.x; x = v.x; y = v.y; } return((sum + x * ys - y * xs) * 0.5); }
static public void shorten_path(VertexSequence vs, double s, int closed) { if (s > 0.0 && vs.size() > 1) { double d; int n = (int)(vs.size() - 2); while (n != 0) { d = vs[n].dist; if (d > s) { break; } vs.RemoveLast(); s -= d; --n; } if (vs.size() < 2) { vs.remove_all(); } else { n = (int)vs.size() - 1; VertexDistance prev = vs[n - 1]; VertexDistance last = vs[n]; d = (prev.dist - s) / prev.dist; double x = prev.x + (last.x - prev.x) * d; double y = prev.y + (last.y - prev.y) * d; last.x = x; last.y = y; if (!prev.IsEqual(last)) { vs.RemoveLast(); } vs.close(closed != 0); } } }