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| -rw-r--r-- | src/helper/geom-pathstroke.cpp | 1158 |
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diff --git a/src/helper/geom-pathstroke.cpp b/src/helper/geom-pathstroke.cpp new file mode 100644 index 0000000..228ea5c --- /dev/null +++ b/src/helper/geom-pathstroke.cpp @@ -0,0 +1,1158 @@ +// SPDX-License-Identifier: GPL-2.0-or-later +/* Authors: + * Liam P. White + * Tavmjong Bah + * Alexander Brock + * + * Copyright (C) 2014-2015 Authors + * + * Released under GNU GPL v2+, read the file 'COPYING' for more information. + */ + +#include <iomanip> +#include <2geom/path-sink.h> +#include <2geom/sbasis-to-bezier.h> // cubicbezierpath_from_sbasis +#include <2geom/path-intersection.h> +#include <2geom/circle.h> + +#include "helper/geom-pathstroke.h" + +namespace Geom { + +static Point intersection_point(Point origin_a, Point vector_a, Point origin_b, Point vector_b) +{ + Coord denom = cross(vector_a, vector_b); + if (!are_near(denom,0.)) { + Coord t = (cross(vector_b, origin_a) + cross(origin_b, vector_b)) / denom; + return origin_a + vector_a*t; + } + return Point(infinity(), infinity()); +} + +/** +* Find circle that touches inside of the curve, with radius matching the curvature, at time value \c t. +* Because this method internally uses unitTangentAt, t should be smaller than 1.0 (see unitTangentAt). +*/ +static Circle touching_circle( D2<SBasis> const &curve, double t, double tol=0.01 ) +{ + D2<SBasis> dM=derivative(curve); + if ( are_near(L2sq(dM(t)), tol) ) { + dM=derivative(dM); + } + if ( are_near(L2sq(dM(t)), tol) ) { // try second time + dM=derivative(dM); + } + Piecewise<D2<SBasis> > unitv = unitVector(dM,tol); + Piecewise<SBasis> dMlength = dot(Piecewise<D2<SBasis> >(dM),unitv); + Piecewise<SBasis> k = cross(derivative(unitv),unitv); + k = divide(k,dMlength,tol,3); + double curv = k(t); // note that this value is signed + + Geom::Point normal = unitTangentAt(curve, t).cw(); + double radius = 1/curv; + Geom::Point center = curve(t) + radius*normal; + return Geom::Circle(center, fabs(radius)); +} + + +// Area of triangle given three corner points +static double area( Geom::Point a, Geom::Point b, Geom::Point c ) { + + using Geom::X; + using Geom::Y; + return( 0.5 * fabs( ( a[X]*(b[Y]-c[Y]) + b[X]*(c[Y]-a[Y]) + c[X]*(a[Y]-b[Y]) ) ) ); +} + +// Alternative touching circle routine directly using Beziers. Works only at end points. +static Circle touching_circle( CubicBezier const &curve, bool start ) { + + double k = 0; + Geom::Point p; + Geom::Point normal; + if ( start ) { + double distance = Geom::distance( curve[1], curve[0] ); + k = 4.0/3.0 * area( curve[0], curve[1], curve[2] ) / + (distance * distance * distance); + if( Geom::cross(curve[0]-curve[1], curve[1]-curve[2]) < 0 ) { + k = -k; + } + p = curve[0]; + normal = Geom::Point(curve[1] - curve[0]).cw(); + normal.normalize(); + // std::cout << "Start k: " << k << " d: " << distance << " normal: " << normal << std::endl; + } else { + double distance = Geom::distance( curve[3], curve[2] ); + k = 4.0/3.0 * area( curve[1], curve[2], curve[3] ) / + (distance * distance * distance); + if( Geom::cross(curve[1]-curve[2], curve[2]-curve[3]) < 0 ) { + k = -k; + } + p = curve[3]; + normal = Geom::Point(curve[3] - curve[2]).cw(); + normal.normalize(); + // std::cout << "End k: " << k << " d: " << distance << " normal: " << normal << std::endl; + } + if( k == 0 ) { + return Geom::Circle( Geom::Point(0,std::numeric_limits<float>::infinity()), + std::numeric_limits<float>::infinity()); + } else { + double radius = 1/k; + Geom::Point center = p + normal * radius; + return Geom::Circle( center, fabs(radius) ); + } +} +} + +namespace { + +// Internal data structure + +struct join_data { + join_data(Geom::Path &_res, Geom::Path const&_outgoing, Geom::Point _in_tang, Geom::Point _out_tang, double _miter, double _width) + : res(_res), outgoing(_outgoing), in_tang(_in_tang), out_tang(_out_tang), miter(_miter), width(_width) {}; + + // contains the current path that is being built on + Geom::Path &res; + + // contains the next curve to append + Geom::Path const& outgoing; + + // input tangents + Geom::Point in_tang; + Geom::Point out_tang; + + // line parameters + double miter; + double width; // half stroke width +}; + +// Join functions must append the outgoing path + +typedef void join_func(join_data jd); + +void bevel_join(join_data jd) +{ + jd.res.appendNew<Geom::LineSegment>(jd.outgoing.initialPoint()); + jd.res.append(jd.outgoing); +} + +void round_join(join_data jd) +{ + jd.res.appendNew<Geom::EllipticalArc>(jd.width, jd.width, 0, false, jd.width <= 0, jd.outgoing.initialPoint()); + jd.res.append(jd.outgoing); +} + +void miter_join_internal(join_data const &jd, bool clip) +{ + using namespace Geom; + + Curve const& incoming = jd.res.back(); + Curve const& outgoing = jd.outgoing.front(); + Path &res = jd.res; + double width = jd.width, miter = jd.miter; + + Point tang1 = jd.in_tang; + Point tang2 = jd.out_tang; + Point p = intersection_point(incoming.finalPoint(), tang1, outgoing.initialPoint(), tang2); + + bool satisfied = false; + bool inc_ls = res.back_open().degreesOfFreedom() <= 4; + + if (p.isFinite()) { + // check size of miter + Point point_on_path = incoming.finalPoint() + rot90(tang1)*width; + // SVG defines miter length as distance between inner intersection and outer intersection, + // which is twice the distance from p to point_on_path but width is half stroke width. + satisfied = distance(p, point_on_path) <= miter * width; + if (satisfied) { + // miter OK, check to see if we can do a relocation + if (inc_ls) { + res.setFinal(p); + } else { + res.appendNew<LineSegment>(p); + } + } else if (clip) { + // std::cout << " Clipping ------------ " << std::endl; + // miter needs clipping, find two points + Point bisector_versor = Line(point_on_path, p).versor(); + Point point_limit = point_on_path + miter * width * bisector_versor; + // std::cout << " bisector_versor: " << bisector_versor << std::endl; + // std::cout << " point_limit: " << point_limit << std::endl; + Point p1 = intersection_point(incoming.finalPoint(), tang1, point_limit, bisector_versor.cw()); + Point p2 = intersection_point(outgoing.initialPoint(), tang2, point_limit, bisector_versor.cw()); + // std::cout << " p1: " << p1 << std::endl; + // std::cout << " p2: " << p2 << std::endl; + if (inc_ls) { + res.setFinal(p1); + } else { + res.appendNew<LineSegment>(p1); + } + res.appendNew<LineSegment>(p2); + } + } + + res.appendNew<LineSegment>(outgoing.initialPoint()); + + // check if we can do another relocation + bool out_ls = outgoing.degreesOfFreedom() <= 4; + + if ((satisfied || clip) && out_ls) { + res.setFinal(outgoing.finalPoint()); + } else { + res.append(outgoing); + } + + // either way, add the rest of the path + res.insert(res.end(), ++jd.outgoing.begin(), jd.outgoing.end()); +} + +void miter_join(join_data jd) { miter_join_internal(jd, false); } +void miter_clip_join(join_data jd) { miter_join_internal(jd, true); } + +Geom::Point pick_solution(std::vector<Geom::ShapeIntersection> points, Geom::Point tang2, Geom::Point endPt) +{ + assert(points.size() == 2); + Geom::Point sol; + if ( dot(tang2, points[0].point() - endPt) > 0 ) { + // points[0] is bad, choose points[1] + sol = points[1]; + } else if ( dot(tang2, points[1].point() - endPt) > 0 ) { // points[0] could be good, now check points[1] + // points[1] is bad, choose points[0] + sol = points[0]; + } else { + // both points are good, choose nearest + sol = ( distanceSq(endPt, points[0].point()) < distanceSq(endPt, points[1].point()) ) + ? points[0].point() : points[1].point(); + } + return sol; +} + +// Arcs line join. If two circles don't intersect, expand inner circle. +Geom::Point expand_circle( Geom::Circle &inner_circle, Geom::Circle const &outer_circle, Geom::Point const &start_pt, Geom::Point const &start_tangent ) { + // std::cout << "expand_circle:" << std::endl; + // std::cout << " outer_circle: radius: " << outer_circle.radius() << " center: " << outer_circle.center() << std::endl; + // std::cout << " start: point: " << start_pt << " tangent: " << start_tangent << std::endl; + + if( !(outer_circle.contains(start_pt) ) ) { + // std::cout << " WARNING: Outer circle does not contain starting point!" << std::endl; + return Geom::Point(0,0); + } + + Geom::Line secant1(start_pt, start_pt + start_tangent); + std::vector<Geom::ShapeIntersection> chord1_pts = outer_circle.intersect(secant1); + // std::cout << " chord1: " << chord1_pts[0].point() << ", " << chord1_pts[1].point() << std::endl; + Geom::LineSegment chord1(chord1_pts[0].point(), chord1_pts[1].point()); + + Geom::Line bisector = make_bisector_line( chord1 ); + std::vector<Geom::ShapeIntersection> chord2_pts = outer_circle.intersect(bisector); + // std::cout << " chord2: " << chord2_pts[0].point() << ", " << chord2_pts[1].point() << std::endl; + Geom::LineSegment chord2(chord2_pts[0].point(), chord2_pts[1].point()); + + // Find D, point on chord2 and on circle closest to start point + Geom::Coord d0 = Geom::distance(chord2_pts[0].point(),start_pt); + Geom::Coord d1 = Geom::distance(chord2_pts[1].point(),start_pt); + // std::cout << " d0: " << d0 << " d1: " << d1 << std::endl; + Geom::Point d = (d0 < d1) ? chord2_pts[0].point() : chord2_pts[1].point(); + Geom::Line da(d,start_pt); + + // Chord through start point and point D + std::vector<Geom::ShapeIntersection> chord3_pts = outer_circle.intersect(da); + // std::cout << " chord3: " << chord3_pts[0].point() << ", " << chord3_pts[1].point() << std::endl; + + // Find farthest point on chord3 and on circle (could be more robust) + Geom::Coord d2 = Geom::distance(chord3_pts[0].point(),d); + Geom::Coord d3 = Geom::distance(chord3_pts[1].point(),d); + // std::cout << " d2: " << d2 << " d3: " << d3 << std::endl; + + // Find point P, the intersection of outer circle and new inner circle + Geom::Point p = (d2 > d3) ? chord3_pts[0].point() : chord3_pts[1].point(); + + // Find center of new circle: it is at the intersection of the bisector + // of the chord defined by the start point and point P and a line through + // the start point and parallel to the first bisector. + Geom::LineSegment chord4(start_pt,p); + Geom::Line bisector2 = make_bisector_line( chord4 ); + Geom::Line diameter = make_parallel_line( start_pt, bisector ); + std::vector<Geom::ShapeIntersection> center_new = bisector2.intersect( diameter ); + // std::cout << " center_new: " << center_new[0].point() << std::endl; + Geom::Coord r_new = Geom::distance( center_new[0].point(), start_pt ); + // std::cout << " r_new: " << r_new << std::endl; + + inner_circle.setCenter( center_new[0].point() ); + inner_circle.setRadius( r_new ); + return p; +} + +// Arcs line join. If two circles don't intersect, adjust both circles so they just touch. +// Increase (decrease) the radius of circle 1 and decrease (increase) of circle 2 by the same amount keeping the given points and tangents fixed. +Geom::Point adjust_circles( Geom::Circle &circle1, Geom::Circle &circle2, Geom::Point const &point1, Geom::Point const &point2, Geom::Point const &tan1, Geom::Point const &tan2 ) { + + Geom::Point n1 = (circle1.center() - point1).normalized(); // Always points towards center + Geom::Point n2 = (circle2.center() - point2).normalized(); + Geom::Point sum_n = n1 + n2; + + double r1 = circle1.radius(); + double r2 = circle2.radius(); + double delta_r = r2 - r1; + Geom::Point c1 = circle1.center(); + Geom::Point c2 = circle2.center(); + Geom::Point delta_c = c2 - c1; + + // std::cout << "adjust_circles:" << std::endl; + // std::cout << " norm: " << n1 << "; " << n2 << std::endl; + // std::cout << " sum_n: " << sum_n << std::endl; + // std::cout << " delta_r: " << delta_r << std::endl; + // std::cout << " delta_c: " << delta_c << std::endl; + + // Quadratic equation + double A = 4 - sum_n.length() * sum_n.length(); + double B = 4.0 * delta_r - 2.0 * Geom::dot( delta_c, sum_n ); + double C = delta_r * delta_r - delta_c.length() * delta_c.length(); + + double s1 = 0; + double s2 = 0; + + if( fabs(A) < 0.01 ) { + // std::cout << " A near zero! $$$$$$$$$$$$$$$$$$" << std::endl; + if( B != 0 ) { + s1 = -C/B; + s2 = -s1; + } + } else { + s1 = (-B + sqrt(B*B - 4*A*C))/(2*A); + s2 = (-B - sqrt(B*B - 4*A*C))/(2*A); + } + + double dr = (fabs(s1)<=fabs(s2)?s1:s2); + + // std::cout << " A: " << A << std::endl; + // std::cout << " B: " << B << std::endl; + // std::cout << " C: " << C << std::endl; + // std::cout << " s1: " << s1 << " s2: " << s2 << " dr: " << dr << std::endl; + + circle1 = Geom::Circle( c1 - dr*n1, r1-dr ); + circle2 = Geom::Circle( c2 + dr*n2, r2+dr ); + + // std::cout << " C1: " << circle1 << std::endl; + // std::cout << " C2: " << circle2 << std::endl; + // std::cout << " d': " << Geom::Point( circle1.center() - circle2.center() ).length() << std::endl; + + Geom::Line bisector( circle1.center(), circle2.center() ); + std::vector<Geom::ShapeIntersection> points = circle1.intersect( bisector ); + Geom::Point p0 = points[0].point(); + Geom::Point p1 = points[1].point(); + // std::cout << " points: " << p0 << "; " << p1 << std::endl; + if( std::abs( Geom::distance( p0, circle2.center() ) - circle2.radius() ) < + std::abs( Geom::distance( p1, circle2.center() ) - circle2.radius() ) ) { + return p0; + } else { + return p1; + } +} + +void extrapolate_join_internal(join_data const &jd, int alternative) +{ + // std::cout << "\nextrapolate_join: entrance: alternative: " << alternative << std::endl; + using namespace Geom; + + Geom::Path &res = jd.res; + Geom::Curve const& incoming = res.back(); + Geom::Curve const& outgoing = jd.outgoing.front(); + Geom::Point startPt = incoming.finalPoint(); + Geom::Point endPt = outgoing.initialPoint(); + Geom::Point tang1 = jd.in_tang; + Geom::Point tang2 = jd.out_tang; + // width is half stroke-width + double width = jd.width, miter = jd.miter; + + // std::cout << " startPt: " << startPt << " endPt: " << endPt << std::endl; + // std::cout << " tang1: " << tang1 << " tang2: " << tang2 << std::endl; + // std::cout << " dot product: " << Geom::dot( tang1, tang2 ) << std::endl; + // std::cout << " width: " << width << std::endl; + + // CIRCLE CALCULATION TESTING + Geom::Circle circle1 = touching_circle(Geom::reverse(incoming.toSBasis()), 0.); + Geom::Circle circle2 = touching_circle(outgoing.toSBasis(), 0); + // std::cout << " circle1: " << circle1 << std::endl; + // std::cout << " circle2: " << circle2 << std::endl; + if( Geom::CubicBezier const * in_bezier = dynamic_cast<Geom::CubicBezier const*>(&incoming) ) { + Geom::Circle circle_test1 = touching_circle(*in_bezier, false); + if( !Geom::are_near( circle1, circle_test1, 0.01 ) ) { + // std::cout << " Circle 1 error!!!!!!!!!!!!!!!!!" << std::endl; + // std::cout << " " << circle_test1 << std::endl; + } + } + if( Geom::CubicBezier const * out_bezier = dynamic_cast<Geom::CubicBezier const*>(&outgoing) ) { + Geom::Circle circle_test2 = touching_circle(*out_bezier, true); + if( !Geom::are_near( circle2, circle_test2, 0.01 ) ) { + // std::cout << " Circle 2 error!!!!!!!!!!!!!!!!!" << std::endl; + // std::cout << " " << circle_test2 << std::endl; + } + } + // END TESTING + + Geom::Point center1 = circle1.center(); + double side1 = tang1[Geom::X]*(startPt[Geom::Y]-center1[Geom::Y]) - tang1[Geom::Y]*(startPt[Geom::X]-center1[Geom::X]); + // std::cout << " side1: " << side1 << std::endl; + + bool inc_ls = !circle1.center().isFinite(); + bool out_ls = !circle2.center().isFinite(); + + std::vector<Geom::ShapeIntersection> points; + + Geom::EllipticalArc *arc1 = nullptr; + Geom::EllipticalArc *arc2 = nullptr; + Geom::LineSegment *seg1 = nullptr; + Geom::LineSegment *seg2 = nullptr; + Geom::Point sol; + Geom::Point p1; + Geom::Point p2; + + if (!inc_ls && !out_ls) { + // std::cout << " two circles" << std::endl; + + // See if tangent is backwards (radius < width/2 and circle is inside stroke). + Geom::Point node_on_path = startPt + Geom::rot90(tang1)*width; + // std::cout << " node_on_path: " << node_on_path << " -------------- " << std::endl; + bool b1 = false; + bool b2 = false; + if (circle1.radius() < width && distance( circle1.center(), node_on_path ) < width) { + b1 = true; + } + if (circle2.radius() < width && distance( circle2.center(), node_on_path ) < width) { + b2 = true; + } + // std::cout << " b1: " << (b1?"true":"false") + // << " b2: " << (b2?"true":"false") << std::endl; + + // Two circles + points = circle1.intersect(circle2); + + if (points.size() != 2) { + // std::cout << " Circles do not intersect, do backup" << std::endl; + switch (alternative) { + case 1: + { + // Fallback to round if one path has radius smaller than half line width. + if(b1 || b2) { + // std::cout << "At one least path has radius smaller than half line width." << std::endl; + return( round_join(jd) ); + } + + Point p; + if( circle2.contains( startPt ) && !circle1.contains( endPt ) ) { + // std::cout << "Expand circle1" << std::endl; + p = expand_circle( circle1, circle2, startPt, tang1 ); + points.emplace_back( 0, 0, p ); + points.emplace_back( 0, 0, p ); + } else if( circle1.contains( endPt ) && !circle2.contains( startPt ) ) { + // std::cout << "Expand circle2" << std::endl; + p = expand_circle( circle2, circle1, endPt, tang2 ); + points.emplace_back( 0, 0, p ); + points.emplace_back( 0, 0, p ); + } else { + // std::cout << "Either both points inside or both outside" << std::endl; + return( miter_clip_join(jd) ); + } + break; + + } + case 2: + { + // Fallback to round if one path has radius smaller than half line width. + if(b1 || b2) { + // std::cout << "At one least path has radius smaller than half line width." << std::endl; + return( round_join(jd) ); + } + + if( ( circle2.contains( startPt ) && !circle1.contains( endPt ) ) || + ( circle1.contains( endPt ) && !circle2.contains( startPt ) ) ) { + + Geom::Point apex = adjust_circles( circle1, circle2, startPt, endPt, tang1, tang2 ); + points.emplace_back( 0, 0, apex ); + points.emplace_back( 0, 0, apex ); + } else { + // std::cout << "Either both points inside or both outside" << std::endl; + return( miter_clip_join(jd) ); + } + + break; + } + case 3: + if( side1 > 0 ) { + Geom::Line secant(startPt, startPt + tang1); + points = circle2.intersect(secant); + circle1.setRadius(std::numeric_limits<float>::infinity()); + circle1.setCenter(Geom::Point(0,std::numeric_limits<float>::infinity())); + } else { + Geom::Line secant(endPt, endPt + tang2); + points = circle1.intersect(secant); + circle2.setRadius(std::numeric_limits<float>::infinity()); + circle2.setCenter(Geom::Point(0,std::numeric_limits<float>::infinity())); + } + break; + + + case 0: + default: + // Do nothing + break; + } + } + + if (points.size() == 2) { + sol = pick_solution(points, tang2, endPt); + if( circle1.radius() != std::numeric_limits<float>::infinity() ) { + arc1 = circle1.arc(startPt, 0.5*(startPt+sol), sol); + } else { + seg1 = new Geom::LineSegment(startPt, sol); + } + if( circle2.radius() != std::numeric_limits<float>::infinity() ) { + arc2 = circle2.arc(sol, 0.5*(sol+endPt), endPt); + } else { + seg2 = new Geom::LineSegment(sol, endPt); + } + } + } else if (inc_ls && !out_ls) { + // Line and circle + // std::cout << " line circle" << std::endl; + points = circle2.intersect(Line(incoming.initialPoint(), incoming.finalPoint())); + if (points.size() == 2) { + sol = pick_solution(points, tang2, endPt); + arc2 = circle2.arc(sol, 0.5*(sol+endPt), endPt); + } + } else if (!inc_ls && out_ls) { + // Circle and line + // std::cout << " circle line" << std::endl; + points = circle1.intersect(Line(outgoing.initialPoint(), outgoing.finalPoint())); + if (points.size() == 2) { + sol = pick_solution(points, tang2, endPt); + arc1 = circle1.arc(startPt, 0.5*(sol+startPt), sol); + } + } + if (points.size() != 2) { + // std::cout << " no solutions" << std::endl; + // no solutions available, fall back to miter + return miter_join(jd); + } + + // We have a solution, thus sol is defined. + p1 = sol; + + // See if we need to clip. Miter length is measured along a circular arc that is tangent to the + // bisector of the incoming and out going angles and passes through the end point (sol) of the + // line join. + + // Center of circle is intersection of a line orthogonal to bisector and a line bisecting + // a chord connecting the path end point (point_on_path) and the join end point (sol). + Geom::Point point_on_path = startPt + Geom::rot90(tang1)*width; + Geom::Line bisector = make_angle_bisector_line(startPt, point_on_path, endPt); + Geom::Line ortho = make_orthogonal_line(point_on_path, bisector); + + Geom::LineSegment chord(point_on_path, sol); + Geom::Line bisector_chord = make_bisector_line(chord); + + Geom::Line limit_line; + double miter_limit = width * miter; + bool clipped = false; + + if (are_parallel(bisector_chord, ortho)) { + // No intersection (can happen if curvatures are equal but opposite) + if (Geom::distance(point_on_path, sol) > miter_limit) { + clipped = true; + Geom::Point temp = bisector.versor(); + Geom::Point limit_point = point_on_path + miter_limit * temp; + limit_line = make_parallel_line( limit_point, ortho ); + } + } else { + Geom::Point center = + Geom::intersection_point( bisector_chord.pointAt(0), bisector_chord.versor(), + ortho.pointAt(0), ortho.versor() ); + Geom::Coord radius = distance(center, point_on_path); + Geom::Circle circle_center(center, radius); + + double limit_angle = miter_limit / radius; + + Geom::Ray start_ray(center, point_on_path); + Geom::Ray end_ray(center, sol); + Geom::Line limit_line(center, 0); // Angle set below + + if (Geom::cross(start_ray.versor(), end_ray.versor()) < 0) { + limit_line.setAngle(start_ray.angle() - limit_angle); + } else { + limit_line.setAngle(start_ray.angle() + limit_angle); + } + + Geom::EllipticalArc *arc_center = circle_center.arc(point_on_path, 0.5*(point_on_path + sol), sol); + if (arc_center && arc_center->sweepAngle() > limit_angle) { + // We need to clip + clipped = true; + + if (!inc_ls) { + // Incoming circular + points = circle1.intersect(limit_line); + if (points.size() == 2) { + p1 = pick_solution(points, tang2, endPt); + delete arc1; + arc1 = circle1.arc(startPt, 0.5*(p1+startPt), p1); + } + } else { + p1 = Geom::intersection_point(startPt, tang1, limit_line.pointAt(0), limit_line.versor()); + } + + if (!out_ls) { + // Outgoing circular + points = circle2.intersect(limit_line); + if (points.size() == 2) { + p2 = pick_solution(points, tang1, endPt); + delete arc2; + arc2 = circle2.arc(p2, 0.5*(p2+endPt), endPt); + } + } else { + p2 = Geom::intersection_point(endPt, tang2, limit_line.pointAt(0), limit_line.versor()); + } + } + } + + // Add initial + if (arc1) { + res.append(*arc1); + } else if (seg1 ) { + res.append(*seg1); + } else { + // Straight line segment: move last point + res.setFinal(p1); + } + + if (clipped) { + res.appendNew<Geom::LineSegment>(p2); + } + + // Add outgoing + if (arc2) { + res.append(*arc2); + res.append(outgoing); + } else if (seg2 ) { + res.append(*seg2); + res.append(outgoing); + } else { + // Straight line segment: + res.appendNew<Geom::LineSegment>(outgoing.finalPoint()); + } + + // add the rest of the path + res.insert(res.end(), ++jd.outgoing.begin(), jd.outgoing.end()); + + delete arc1; + delete arc2; + delete seg1; + delete seg2; +} + +void extrapolate_join( join_data jd) { extrapolate_join_internal(jd, 0); } +void extrapolate_join_alt1(join_data jd) { extrapolate_join_internal(jd, 1); } +void extrapolate_join_alt2(join_data jd) { extrapolate_join_internal(jd, 2); } +void extrapolate_join_alt3(join_data jd) { extrapolate_join_internal(jd, 3); } + + +void tangents(Geom::Point tang[2], Geom::Curve const& incoming, Geom::Curve const& outgoing) +{ + Geom::Point tang1 = Geom::unitTangentAt(reverse(incoming.toSBasis()), 0.); + Geom::Point tang2 = outgoing.unitTangentAt(0.); + tang[0] = tang1, tang[1] = tang2; +} + +// Offsetting a line segment is mathematically stable and quick to do +Geom::LineSegment offset_line(Geom::LineSegment const& l, double width) +{ + Geom::Point tang1 = Geom::rot90(l.unitTangentAt(0)); + Geom::Point tang2 = Geom::rot90(unitTangentAt(reverse(l.toSBasis()), 0.)); + + Geom::Point start = l.initialPoint() + tang1 * width; + Geom::Point end = l.finalPoint() - tang2 * width; + + return Geom::LineSegment(start, end); +} + +void get_cubic_data(Geom::CubicBezier const& bez, double time, double& len, double& rad) +{ + // get derivatives + std::vector<Geom::Point> derivs = bez.pointAndDerivatives(time, 3); + + Geom::Point der1 = derivs[1]; // first deriv (tangent vector) + Geom::Point der2 = derivs[2]; // second deriv (tangent's tangent) + double l = Geom::L2(der1); // length + + len = rad = 0; + + // TODO: we might want to consider using Geom::touching_circle to determine the + // curvature radius here. Less code duplication, but slower + + if (Geom::are_near(l, 0, 1e-4)) { + l = Geom::L2(der2); + Geom::Point der3 = derivs.at(3); // try second time + if (Geom::are_near(l, 0, 1e-4)) { + l = Geom::L2(der3); + if (Geom::are_near(l, 0)) { + return; // this isn't a segment... + } + rad = 1e8; + } else { + rad = -l * (Geom::dot(der2, der2) / Geom::cross(der2, der3)); + } + } else { + rad = -l * (Geom::dot(der1, der1) / Geom::cross(der1, der2)); + } + len = l; +} + +double _offset_cubic_stable_sub( + Geom::CubicBezier const& bez, + Geom::CubicBezier& c, + const Geom::Point& start_normal, + const Geom::Point& end_normal, + const Geom::Point& start_new, + const Geom::Point& end_new, + const double start_rad, + const double end_rad, + const double start_len, + const double end_len, + const double width, + const double width_correction) { + using Geom::X; + using Geom::Y; + + double start_off = 1, end_off = 1; + // correction of the lengths of the tangent to the offset + if (!Geom::are_near(start_rad, 0)) + start_off += (width + width_correction) / start_rad; + if (!Geom::are_near(end_rad, 0)) + end_off += (width + width_correction) / end_rad; + + // We don't change the direction of the control points + if (start_off < 0) { + start_off = 0; + } + if (end_off < 0) { + end_off = 0; + } + start_off *= start_len; + end_off *= end_len; + // -------- + + Geom::Point mid1_new = start_normal.ccw()*start_off; + mid1_new = Geom::Point(start_new[X] + mid1_new[X]/3., start_new[Y] + mid1_new[Y]/3.); + Geom::Point mid2_new = end_normal.ccw()*end_off; + mid2_new = Geom::Point(end_new[X] - mid2_new[X]/3., end_new[Y] - mid2_new[Y]/3.); + + // create the estimate curve + c = Geom::CubicBezier(start_new, mid1_new, mid2_new, end_new); + + // check the tolerance for our estimate to be a parallel curve + + double worst_residual = 0; + for (size_t ii = 3; ii <= 7; ii+=2) { + const double t = static_cast<double>(ii) / 10; + const Geom::Point req = bez.pointAt(t); + const Geom::Point chk = c.pointAt(c.nearestTime(req)); + const double current_residual = (chk-req).length() - std::abs(width); + if (std::abs(current_residual) > std::abs(worst_residual)) { + worst_residual = current_residual; + } + } + return worst_residual; +} + +void offset_cubic(Geom::Path& p, Geom::CubicBezier const& bez, double width, double tol, size_t levels) +{ + using Geom::X; + using Geom::Y; + + const Geom::Point start_pos = bez.initialPoint(); + const Geom::Point end_pos = bez.finalPoint(); + + const Geom::Point start_normal = Geom::rot90(bez.unitTangentAt(0)); + const Geom::Point end_normal = -Geom::rot90(Geom::unitTangentAt(Geom::reverse(bez.toSBasis()), 0.)); + + // offset the start and end control points out by the width + const Geom::Point start_new = start_pos + start_normal*width; + const Geom::Point end_new = end_pos + end_normal*width; + + // -------- + double start_rad, end_rad; + double start_len, end_len; // tangent lengths + get_cubic_data(bez, 0, start_len, start_rad); + get_cubic_data(bez, 1, end_len, end_rad); + + + Geom::CubicBezier c; + + double best_width_correction = 0; + double best_residual = _offset_cubic_stable_sub( + bez, c, + start_normal, end_normal, + start_new, end_new, + start_rad, end_rad, + start_len, end_len, + width, best_width_correction); + double stepsize = std::abs(width)/2; + bool seen_success = false; + double stepsize_threshold = 0; + // std::cout << "Residual from " << best_residual << " "; + size_t ii = 0; + for (; ii < 100 && stepsize > stepsize_threshold; ++ii) { + bool success = false; + const double width_correction = best_width_correction - (best_residual > 0 ? 1 : -1) * stepsize; + Geom::CubicBezier current_curve; + const double residual = _offset_cubic_stable_sub( + bez, current_curve, + start_normal, end_normal, + start_new, end_new, + start_rad, end_rad, + start_len, end_len, + width, width_correction); + if (std::abs(residual) < std::abs(best_residual)) { + best_residual = residual; + best_width_correction = width_correction; + c = current_curve; + success = true; + if (std::abs(best_residual) < tol/4) { + break; + } + } + + if (success) { + if (!seen_success) { + seen_success = true; + //std::cout << "Stepsize factor: " << std::abs(width) / stepsize << std::endl; + stepsize_threshold = stepsize / 1000; + } + } + else { + stepsize /= 2; + } + if (std::abs(best_width_correction) >= std::abs(width)/2) { + //break; // Seems to prevent some numerical instabilities, not clear if useful + } + } + + // reached maximum recursive depth + // don't bother with any more correction + if (levels == 0) { + try { + p.append(c); + } + catch (...) { + if ((p.finalPoint() - c.initialPoint()).length() < 1e-6) { + c.setInitial(p.finalPoint()); + } + else { + auto line = Geom::LineSegment(p.finalPoint(), c.initialPoint()); + p.append(line); + } + p.append(c); + } + + return; + } + + // We find the point on our new curve (c) for which the distance between + // (c) and (bez) differs the most from the desired distance (width). + double worst_err = std::abs(best_residual); + double worst_time = .5; + for (size_t ii = 1; ii <= 9; ++ii) { + const double t = static_cast<double>(ii) / 10; + const Geom::Point req = bez.pointAt(t); + // We use the exact solution with nearestTime because it is numerically + // much more stable than simply assuming that the point on (c) closest + // to bez.pointAt(t) is given by c.pointAt(t) + const Geom::Point chk = c.pointAt(c.nearestTime(req)); + + Geom::Point const diff = req - chk; + const double err = std::abs(diff.length() - std::abs(width)); + if (err > worst_err) { + worst_err = err; + worst_time = t; + } + } + + if (worst_err < tol) { + if (Geom::are_near(start_new, p.finalPoint())) { + p.setFinal(start_new); // if it isn't near, we throw + } + + // we're good, curve is accurate enough + p.append(c); + return; + } else { + // split the curve in two + std::pair<Geom::CubicBezier, Geom::CubicBezier> s = bez.subdivide(worst_time); + offset_cubic(p, s.first, width, tol, levels - 1); + offset_cubic(p, s.second, width, tol, levels - 1); + } +} + +void offset_quadratic(Geom::Path& p, Geom::QuadraticBezier const& bez, double width, double tol, size_t levels) +{ + // cheat + // it's faster + // seriously + std::vector<Geom::Point> points = bez.controlPoints(); + Geom::Point b1 = points[0] + (2./3) * (points[1] - points[0]); + Geom::Point b2 = b1 + (1./3) * (points[2] - points[0]); + Geom::CubicBezier cub = Geom::CubicBezier(points[0], b1, b2, points[2]); + offset_cubic(p, cub, width, tol, levels); +} + +void offset_curve(Geom::Path& res, Geom::Curve const* current, double width, double tolerance) +{ + size_t levels = 8; + + if (current->isDegenerate()) return; // don't do anything + + // TODO: we can handle SVGEllipticalArc here as well, do that! + + if (Geom::BezierCurve const *b = dynamic_cast<Geom::BezierCurve const*>(current)) { + size_t order = b->order(); + switch (order) { + case 1: + res.append(offset_line(static_cast<Geom::LineSegment const&>(*current), width)); + break; + case 2: { + Geom::QuadraticBezier const& q = static_cast<Geom::QuadraticBezier const&>(*current); + offset_quadratic(res, q, width, tolerance, levels); + break; + } + case 3: { + Geom::CubicBezier const& cb = static_cast<Geom::CubicBezier const&>(*current); + offset_cubic(res, cb, width, tolerance, levels); + break; + } + default: { + Geom::Path sbasis_path = Geom::cubicbezierpath_from_sbasis(current->toSBasis(), tolerance); + for (const auto & i : sbasis_path) + offset_curve(res, &i, width, tolerance); + break; + } + } + } else { + Geom::Path sbasis_path = Geom::cubicbezierpath_from_sbasis(current->toSBasis(), 0.1); + for (const auto & i : sbasis_path) + offset_curve(res, &i, width, tolerance); + } +} + +typedef void cap_func(Geom::PathBuilder& res, Geom::Path const& with_dir, Geom::Path const& against_dir, double width); + +void flat_cap(Geom::PathBuilder& res, Geom::Path const&, Geom::Path const& against_dir, double) +{ + res.lineTo(against_dir.initialPoint()); +} + +void round_cap(Geom::PathBuilder& res, Geom::Path const&, Geom::Path const& against_dir, double width) +{ + res.arcTo(width / 2., width / 2., 0., true, false, against_dir.initialPoint()); +} + +void square_cap(Geom::PathBuilder& res, Geom::Path const& with_dir, Geom::Path const& against_dir, double width) +{ + width /= 2.; + Geom::Point normal_1 = -Geom::unitTangentAt(Geom::reverse(with_dir.back().toSBasis()), 0.); + Geom::Point normal_2 = -against_dir[0].unitTangentAt(0.); + res.lineTo(with_dir.finalPoint() + normal_1*width); + res.lineTo(against_dir.initialPoint() + normal_2*width); + res.lineTo(against_dir.initialPoint()); +} + +void peak_cap(Geom::PathBuilder& res, Geom::Path const& with_dir, Geom::Path const& against_dir, double width) +{ + width /= 2.; + Geom::Point normal_1 = -Geom::unitTangentAt(Geom::reverse(with_dir.back().toSBasis()), 0.); + Geom::Point normal_2 = -against_dir[0].unitTangentAt(0.); + Geom::Point midpoint = ((with_dir.finalPoint() + normal_1*width) + (against_dir.initialPoint() + normal_2*width)) * 0.5; + res.lineTo(midpoint); + res.lineTo(against_dir.initialPoint()); +} + +} // namespace + +namespace Inkscape { + +Geom::PathVector outline( + Geom::Path const& input, + double width, + double miter, + LineJoinType join, + LineCapType butt, + double tolerance) +{ + if (input.size() == 0) return Geom::PathVector(); // nope, don't even try + + Geom::PathBuilder res; + Geom::Path with_dir = half_outline(input, width/2., miter, join, tolerance); + Geom::Path against_dir = half_outline(input.reversed(), width/2., miter, join, tolerance); + res.moveTo(with_dir[0].initialPoint()); + res.append(with_dir); + + cap_func *cf; + switch (butt) { + case BUTT_ROUND: + cf = &round_cap; + break; + case BUTT_SQUARE: + cf = &square_cap; + break; + case BUTT_PEAK: + cf = &peak_cap; + break; + default: + cf = &flat_cap; + } + + // glue caps + if (!input.closed()) { + cf(res, with_dir, against_dir, width); + } else { + res.closePath(); + res.moveTo(against_dir.initialPoint()); + } + + res.append(against_dir); + + if (!input.closed()) { + cf(res, against_dir, with_dir, width); + } + + res.closePath(); + res.flush(); + return res.peek(); +} + +Geom::Path half_outline( + Geom::Path const& input, + double width, + double miter, + LineJoinType join, + double tolerance) +{ + if (tolerance <= 0) { + if (std::abs(width) > 0) { + tolerance = 5.0 * (std::abs(width)/100); + } + else { + tolerance = 1e-4; + } + } + Geom::Path res; + if (input.size() == 0) return res; + + Geom::Point tang1 = input[0].unitTangentAt(0); + Geom::Point start = input.initialPoint() + tang1 * width; + Geom::Path temp; + Geom::Point tang[2]; + + res.setStitching(true); + temp.setStitching(true); + + res.start(start); + + // Do two curves at a time for efficiency, since the join function needs to know the outgoing curve as well + const Geom::Curve &closingline = input.back_closed(); + const size_t k = (are_near(closingline.initialPoint(), closingline.finalPoint()) && input.closed() ) + ?input.size_open():input.size_default(); + + for (size_t u = 0; u < k; u += 2) { + temp.clear(); + + offset_curve(temp, &input[u], width, tolerance); + + // on the first run through, there isn't a join + if (u == 0) { + res.append(temp); + } else { + tangents(tang, input[u-1], input[u]); + outline_join(res, temp, tang[0], tang[1], width, miter, join); + } + + // odd number of paths + if (u < k - 1) { + temp.clear(); + offset_curve(temp, &input[u+1], width, tolerance); + tangents(tang, input[u], input[u+1]); + outline_join(res, temp, tang[0], tang[1], width, miter, join); + } + } + if (input.closed()) { + Geom::Curve const &c1 = res.back(); + Geom::Curve const &c2 = res.front(); + temp.clear(); + temp.append(c1); + Geom::Path temp2; + temp2.append(c2); + tangents(tang, input.back(), input.front()); + outline_join(temp, temp2, tang[0], tang[1], width, miter, join); + res.erase(res.begin()); + res.erase_last(); + res.append(temp); + res.close(); + } + return res; +} + +void outline_join(Geom::Path &res, Geom::Path const& temp, Geom::Point in_tang, Geom::Point out_tang, double width, double miter, Inkscape::LineJoinType join) +{ + if (res.size() == 0 || temp.size() == 0) + return; + Geom::Curve const& outgoing = temp.front(); + if (Geom::are_near(res.finalPoint(), outgoing.initialPoint(), 0.01)) { + // if the points are /that/ close, just ignore this one + res.setFinal(temp.initialPoint()); + res.append(temp); + return; + } + + join_data jd(res, temp, in_tang, out_tang, miter, width); + if (!(Geom::cross(in_tang, out_tang) > 0)) { + join = Inkscape::JOIN_BEVEL; + } + join_func *jf; + switch (join) { + case Inkscape::JOIN_BEVEL: + jf = &bevel_join; + break; + case Inkscape::JOIN_ROUND: + jf = &round_join; + break; + case Inkscape::JOIN_EXTRAPOLATE: + jf = &extrapolate_join; + break; + case Inkscape::JOIN_EXTRAPOLATE1: + jf = &extrapolate_join_alt1; + break; + case Inkscape::JOIN_EXTRAPOLATE2: + jf = &extrapolate_join_alt2; + break; + case Inkscape::JOIN_EXTRAPOLATE3: + jf = &extrapolate_join_alt3; + break; + case Inkscape::JOIN_MITER_CLIP: + jf = &miter_clip_join; + break; + default: + jf = &miter_join; + } + jf(jd); + } + +} // namespace Inkscape + +/* + Local Variables: + mode:c++ + c-file-style:"stroustrup" + c-file-offsets:((innamespace . 0)(inline-open . 0)(case-label . +)) + indent-tabs-mode:nil + fill-column:99 + End: +*/ +// vim: filetype=cpp:expandtab:shiftwidth=4:tabstop=8:softtabstop=4:fileencoding=utf-8 : |