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LibGfx: Implement cubic bezier curves by splitting them to subcurves

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This makes them significantly more nicer-looking, and fixes a FIXME :^)
This commit is contained in:
Ali Mohammad Pur 2021-09-17 18:42:30 +04:30 • committed by Ali Mohammad Pur
parent 02d949cfb6
commit 433725fef2
6 changed files with 145 additions and 12 deletions
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78
Userland/Libraries/LibGfx/Painter.cpp
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@ -1858,6 +1858,76 @@ void Painter::draw_quadratic_bezier_curve(IntPoint const& control_point, IntPoin
});
}
void Painter::for_each_line_segment_on_cubic_bezier_curve(FloatPoint const& control_point_0, FloatPoint const& control_point_1, FloatPoint const& p1, FloatPoint const& p2, Function<void(FloatPoint const&, FloatPoint const&)>&& callback)
{
for_each_line_segment_on_cubic_bezier_curve(control_point_0, control_point_1, p1, p2, callback);
}
static bool can_approximate_cubic_bezier_curve(FloatPoint const& p1, FloatPoint const& p2, FloatPoint const& control_0, FloatPoint const& control_1)
{
constexpr float tolerance = 15; // Arbitrary, seems like 10-30 produces nice results.
auto ax = 3 * control_0.x() - 2 * p1.x() - p2.x();
auto ay = 3 * control_0.y() - 2 * p1.y() - p2.y();
auto bx = 3 * control_1.x() - p1.x() - 2 * p2.x();
auto by = 3 * control_1.y() - p1.y() - 2 * p2.y();
ax *= ax;
ay *= ay;
bx *= bx;
by *= by;
return max(ax, bx) + max(ay, by) <= tolerance;
}
// static
void Painter::for_each_line_segment_on_cubic_bezier_curve(FloatPoint const& control_point_0, FloatPoint const& control_point_1, FloatPoint const& p1, FloatPoint const& p2, Function<void(FloatPoint const&, FloatPoint const&)>& callback)
{
struct ControlPair {
FloatPoint control_point_0;
FloatPoint control_point_1;
};
struct SegmentDescriptor {
ControlPair control_points;
FloatPoint p1;
FloatPoint p2;
};
static constexpr auto split_cubic_bezier_curve = [](ControlPair const& original_controls, FloatPoint const& p1, FloatPoint const& p2, auto& segments) {
Array level_1_midpoints {
(p1 + original_controls.control_point_0) / 2,
(original_controls.control_point_0 + original_controls.control_point_1) / 2,
(original_controls.control_point_1 + p2) / 2,
};
Array level_2_midpoints {
(level_1_midpoints[0] + level_1_midpoints[1]) / 2,
(level_1_midpoints[1] + level_1_midpoints[2]) / 2,
};
auto level_3_midpoint = (level_2_midpoints[0] + level_2_midpoints[1]) / 2;
segments.enqueue({ { level_1_midpoints[0], level_2_midpoints[0] }, p1, level_3_midpoint });
segments.enqueue({ { level_2_midpoints[1], level_1_midpoints[2] }, level_3_midpoint, p2 });
};
Queue<SegmentDescriptor> segments;
segments.enqueue({ { control_point_0, control_point_1 }, p1, p2 });
while (!segments.is_empty()) {
auto segment = segments.dequeue();
if (can_approximate_cubic_bezier_curve(segment.p1, segment.p2, segment.control_points.control_point_0, segment.control_points.control_point_1))
callback(segment.p1, segment.p2);
else
split_cubic_bezier_curve(segment.control_points, segment.p1, segment.p2, segments);
}
}
void Painter::draw_cubic_bezier_curve(IntPoint const& control_point_0, IntPoint const& control_point_1, IntPoint const& p1, IntPoint const& p2, Color color, int thickness, Painter::LineStyle style)
{
for_each_line_segment_on_cubic_bezier_curve(FloatPoint(control_point_0), FloatPoint(control_point_1), FloatPoint(p1), FloatPoint(p2), [&](FloatPoint const& fp1, FloatPoint const& fp2) {
draw_line(IntPoint(fp1.x(), fp1.y()), IntPoint(fp2.x(), fp2.y()), color, thickness, style);
});
}
// static
void Painter::for_each_line_segment_on_elliptical_arc(FloatPoint const& p1, FloatPoint const& p2, FloatPoint const& center, FloatPoint const radii, float x_axis_rotation, float theta_1, float theta_delta, Function<void(FloatPoint const&, FloatPoint const&)>& callback)
{
@ -1975,6 +2045,14 @@ void Painter::stroke_path(Path const& path, Color color, int thickness)
cursor = segment.point();
break;
}
case Segment::Type::CubicBezierCurveTo: {
auto& curve = static_cast<CubicBezierCurveSegment const&>(segment);
auto& through_0 = curve.through_0();
auto& through_1 = curve.through_1();
draw_cubic_bezier_curve(through_0.to_type<int>(), through_1.to_type<int>(), cursor.to_type<int>(), segment.point().to_type<int>(), color, thickness);
cursor = segment.point();
break;
}
case Segment::Type::EllipticalArcTo:
auto& arc = static_cast<EllipticalArcSegment const&>(segment);
draw_elliptical_arc(cursor.to_type<int>(), segment.point().to_type<int>(), arc.center().to_type<int>(), arc.radii(), arc.x_axis_rotation(), arc.theta_1(), arc.theta_delta(), color, thickness);