xp[0] = x + w + 4; yp[0] = y - a + 1;
xp[1] = x + w; yp[1] = y + d;
xp[2] = x + w - 2; yp[2] = y + (d - a)/2 + 2;
xp[3] = x + w - 5; yp[3] = y + (d - a)/2 + 4;
xp[0] = x + w + 4; yp[0] = y - a + 1;
xp[1] = x + w; yp[1] = y + d;
xp[2] = x + w - 2; yp[2] = y + (d - a)/2 + 2;
xp[3] = x + w - 5; yp[3] = y + (d - a)/2 + 4;