* blotdiameter along all edges of the polygon (which is what the
* postscript routine in the backend effectively does, but on the
* shrinked polygon). --jr
+ *
+ * An extra parameter "extroversion" has been added since staying just
+ * inside of a polygon will reduce its visual size when tracing a
+ * rounded path. If extroversion is zero, the polygon is just traced
+ * as-is. If it is -1 (the default) the drawing will stay just within
+ * the given polygon. If it is 1, the traced line will stay just
+ * outside of the given polygon.
*/
Stencil
Lookup::round_filled_polygon (vector<Offset> const &points,
- Real blotdiameter)
+ Real blotdiameter,
+ Real extroversion)
{
/* TODO: Maybe print a warning if one of the above limitations
applies to the given polygon. However, this is quite complicated
return Stencil ();
if (points.size () == 1)
{
- Stencil circ = circle (0.5 * blotdiameter, 0, true);
+ Stencil circ = circle (0.5 * (1.0 + extroversion) * blotdiameter, 0, true);
circ.translate (points[0]);
return circ;
}
if (points.size () == 2)
- return Line_interface::make_line (blotdiameter, points[0], points[1]);
-
- /* shrink polygon in size by 0.5 * blotdiameter */
-
- // first we need to determine the orientation of the polygon in
- // order to decide whether shrinking means moving the polygon to the
- // left or to the right of the outline. We do that by calculating
- // (double) the oriented area of the polygon. We first determine the
- // center and do the area calculations relative to it.
- // Mathematically, the result is not affected by this shift, but
- // numerically a lot of cancellation is going on and this keeps its
- // effects in check.
-
- Offset center;
- for (vsize i = 0; i < points.size (); i++)
- center += points[i];
- center /= points.size ();
+ return Line_interface::make_line ((1.0 + extroversion) * blotdiameter, points[0], points[1]);
- Real area = 0.0;
- Offset last = points.back () - center;
+ vector<Offset> shrunk_points;
- for (vsize i = 0; i < points.size (); i++)
+ if (extroversion == 0.0)
{
- Offset here = points[i] - center;
- area += cross_product (last, here);
- last = here;
+ shrunk_points = points;
}
-
- bool ccw = area >= 0.0; // true if whole shape is counterclockwise oriented
-
- vector<Offset> shrunk_points;
- shrunk_points.resize (points.size ());
-
- for (vsize i = 0; i < points.size (); i++)
+ else
{
- int i0 = i;
- int i1 = (i + 1) % points.size ();
- int i2 = (i + 2) % points.size ();
- Offset p0 = points[i0];
- Offset p1 = points[i1];
- Offset p2 = points[i2];
- Offset p01 = p1 - p0;
- Offset p12 = p2 - p1;
- Offset inward0 = Offset(-p01[Y_AXIS], p01[X_AXIS]).direction ();
- Offset inward2 = Offset(-p12[Y_AXIS], p12[X_AXIS]).direction ();
-
- if (!ccw)
+ /* shrink polygon in size by 0.5 * blotdiameter */
+
+ // first we need to determine the orientation of the polygon in
+ // order to decide whether shrinking means moving the polygon to the
+ // left or to the right of the outline. We do that by calculating
+ // (double) the oriented area of the polygon. We first determine the
+ // center and do the area calculations relative to it.
+ // Mathematically, the result is not affected by this shift, but
+ // numerically a lot of cancellation is going on and this keeps its
+ // effects in check.
+
+ Offset center;
+ for (vsize i = 0; i < points.size (); i++)
+ center += points[i];
+ center /= points.size ();
+
+ Real area = 0.0;
+ Offset last = points.back () - center;
+
+ for (vsize i = 0; i < points.size (); i++)
{
- inward0 = -inward0;
- inward2 = -inward2;
+ Offset here = points[i] - center;
+ area += cross_product (last, here);
+ last = here;
}
- Offset middle = 0.5*(inward0 + inward2);
-
- // "middle" now is a vector in the right direction for the
- // shrinkage. Its size needs to be large enough that the
- // projection on either of the inward vectors has a size of 1.
-
- Real proj = dot_product (middle, inward0);
+ bool ccw = area >= 0.0; // true if whole shape is counterclockwise oriented
- // What's the size of proj? Assuming that we have a corner
- // angle of phi where 0 corresponds to a continuing line, the
- // length of middle is 0.5 |(1+cos phi, sin phi)| = cos (phi/2),
- // so its projection has length
- // cos^2 (phi/2) = 0.5 + 0.5 cos (phi).
- // We don't really want to move inwards more than 3 blob
- // diameters corresponding to 6 blob radii. So
- // cos (phi/2) = 1/6 gives phi ~ 161, meaning that a 20 degree
- // corner necessitates moving 3 blob diameters from the corner
- // in order to stay inside the lines. Ruler and circle agree.
- // 0.03 is close enough to 1/36. Basically we want to keep the
- // shape from inverting from pulling too far inward.
- // 3 diameters is pretty much a handwaving guess.
+ shrunk_points.resize (points.size ());
- if (abs (proj) < 0.03)
- proj = proj < 0 ? -0.03 : 0.03;
+ for (vsize i = 0; i < points.size (); i++)
+ {
+ int i0 = i;
+ int i1 = (i + 1) % points.size ();
+ int i2 = (i + 2) % points.size ();
+ Offset p0 = points[i0];
+ Offset p1 = points[i1];
+ Offset p2 = points[i2];
+ Offset p01 = p1 - p0;
+ Offset p12 = p2 - p1;
+ Offset inward0 = Offset(-p01[Y_AXIS], p01[X_AXIS]).direction ();
+ Offset inward2 = Offset(-p12[Y_AXIS], p12[X_AXIS]).direction ();
+
+ if (!ccw)
+ {
+ inward0 = -inward0;
+ inward2 = -inward2;
+ }
- shrunk_points[i1] = p1 + (0.5 * blotdiameter / proj) * middle;
+ Offset middle = 0.5*(inward0 + inward2);
+
+ // "middle" now is a vector in the right direction for the
+ // shrinkage. Its size needs to be large enough that the
+ // projection on either of the inward vectors has a size of 1.
+
+ Real proj = dot_product (middle, inward0);
+
+ // What's the size of proj? Assuming that we have a corner
+ // angle of phi where 0 corresponds to a continuing line, the
+ // length of middle is 0.5 |(1+cos phi, sin phi)| = cos (phi/2),
+ // so its projection has length
+ // cos^2 (phi/2) = 0.5 + 0.5 cos (phi).
+ // We don't really want to move inwards more than 3 blob
+ // diameters corresponding to 6 blob radii. So
+ // cos (phi/2) = 1/6 gives phi ~ 161, meaning that a 20 degree
+ // corner necessitates moving 3 blob diameters from the corner
+ // in order to stay inside the lines. Ruler and circle agree.
+ // 0.03 is close enough to 1/36. Basically we want to keep the
+ // shape from inverting from pulling too far inward.
+ // 3 diameters is pretty much a handwaving guess.
+
+ if (abs (proj) < 0.03)
+ proj = proj < 0 ? -0.03 : 0.03;
+
+ shrunk_points[i1] = p1 - (0.5 * blotdiameter / proj) * middle
+ * extroversion;
+ }
}
/* build scm expression and bounding box */
SCM shrunk_points_scm = SCM_EOL;
Box box;
+ Box shrunk_box;
for (vsize i = 0; i < shrunk_points.size (); i++)
{
SCM x = scm_from_double (shrunk_points[i][X_AXIS]);
SCM y = scm_from_double (shrunk_points[i][Y_AXIS]);
shrunk_points_scm = scm_cons (x, scm_cons (y, shrunk_points_scm));
box.add_point (points[i]);
+ shrunk_box.add_point (shrunk_points[i]);
}
+ shrunk_box.widen (0.5*blotdiameter, 0.5*blotdiameter);
+ box.unite (shrunk_box);
SCM polygon_scm = scm_list_n (ly_symbol2scm ("polygon"),
ly_quote_scm (shrunk_points_scm),
scm_from_double (blotdiameter),
SCM_UNDEFINED);
Stencil polygon = Stencil (box, polygon_scm);
- shrunk_points.clear ();
return polygon;
}
}
LY_DEFINE (ly_round_filled_polygon, "ly:round-filled-polygon",
- 2, 0, 0,
- (SCM points, SCM blot),
+ 2, 1, 0,
+ (SCM points, SCM blot, SCM extroversion),
"Make a @code{Stencil} object that prints a black polygon with"
" corners at the points defined by @var{points} (list of coordinate"
- " pairs) and roundness @var{blot}.")
+ " pairs) and roundness @var{blot}. Optional"
+ "@var{extroversion} shifts the outline outward, with the"
+ "default of@tie{}@code{-1.0} keeping the outer boundary of"
+ "the outline just inside of the polygon.")
{
SCM_ASSERT_TYPE (scm_ilength (points) > 0, points, SCM_ARG1, __FUNCTION__, "list of coordinate pairs");
LY_ASSERT_TYPE (scm_is_number, blot, 2);
+ Real ext = -1;
+ if (!SCM_UNBNDP (extroversion))
+ {
+ LY_ASSERT_TYPE (scm_is_number, extroversion, 3);
+ ext = scm_to_double (extroversion);
+ }
vector<Offset> pts;
for (SCM p = points; scm_is_pair (p); p = scm_cdr (p))
{
// TODO: Print out warning
}
}
- return Lookup::round_filled_polygon (pts, scm_to_double (blot)).smobbed_copy ();
+ return Lookup::round_filled_polygon (pts, scm_to_double (blot), ext)
+ .smobbed_copy ();
}
LY_DEFINE (ly_register_stencil_expression, "ly:register-stencil-expression",
projects / lilypond.git / commitdiff