+bezier

lib/src/bezier.dart

@@ -0,0 +1,143 @@
+import 'dart:math';
+import 'dart:ui';
+
+double bezierLength(Bezier bezier, [double steps = 10]) {
+  assert(bezier != null && steps != 0);
+  final step = 1 / steps;
+  var c = bezier.point(0);
+  var length = 0.0;
+  for (var t = step; t <= 1; t += step) {
+    final p = bezier.point(t);
+    length += (p - c).distance;
+    c = p;
+  }
+  return length;
+}
+
+abstract class Bezier {
+  Offset point(double t);
+
+  double get length => bezierLength(this);
+}
+
+class LinearBezier extends Bezier {
+  Offset p0, p1;
+
+  LinearBezier(this.p0, this.p1);
+
+  Offset point(double t) {
+    return p0 + (p1 - p0) * t;
+  }
+
+  double get length => (p1 - p0).distance;
+}
+
+class QuadraticBezier extends Bezier {
+  double _quadraticBezier(double t, double p0, double p1, double p2) {
+    //final lt = 1 - t;
+    //return lt * (lt * p0 + t * p1) + t * (lt * p1 + t * p2);
+    //return pow(1 - t, 2) * p0 + 2 * (1 - t) * t * p1 + pow(t, 2) * p2;
+    return p1 + pow(1 - t, 2) * (p0 - p1) + pow(t, 2) * (p2 - p1);
+  }
+
+  Offset p0, p1, p2;
+
+  QuadraticBezier(this.p0, this.p1, this.p2);
+
+  Offset point(double t) {
+    return Offset(
+      _quadraticBezier(t, p0.dx, p1.dx, p2.dx),
+      _quadraticBezier(t, p0.dy, p1.dy, p2.dy),
+    );
+  }
+}
+
+class CubicBezier extends Bezier {
+  double _cubicBezier(double t, double p0, double p1, double p2, double p3) {
+    return pow(1 - t, 3) * p0 +
+        3 * t * pow(1 - t, 2) * p1 +
+        3 * pow(t, 2) * (1 - t) * p2 +
+        pow(t, 3) * p3;
+  }
+
+  Offset p0, p1, p2, p3;
+
+  CubicBezier(this.p0, this.p1, this.p2, this.p3);
+
+  Offset point(double t) => Offset(
+        _cubicBezier(t, p0.dx, p1.dx, p2.dx, p3.dx),
+        _cubicBezier(t, p0.dy, p1.dy, p2.dy, p3.dy),
+      );
+}
+
+class PathBezier extends Bezier {
+  double _length = 0;
+
+  double get length => _length;
+
+  List<Bezier> _curves = [];
+  List<double> _lens = [];
+
+  final Offset p0;
+  Offset _p0;
+
+  PathBezier(this.p0) : _p0 = p0;
+
+  static PathBezier roundedRect(RRect rrect) {
+    return PathBezier(Offset(rrect.left + rrect.tlRadiusX, rrect.top))
+      ..lineTo(Offset(rrect.right - rrect.trRadiusX, rrect.top))
+      ..quadTo(
+          Offset(rrect.right, rrect.top), Offset(rrect.right, rrect.trRadiusY))
+      ..lineTo(Offset(rrect.right, rrect.bottom - rrect.brRadiusY))
+      ..quadTo(Offset(rrect.right, rrect.bottom),
+          Offset(rrect.right - rrect.brRadiusX, rrect.bottom))
+      ..lineTo(Offset(rrect.left + rrect.brRadiusX, rrect.bottom))
+      ..quadTo(Offset(rrect.left, rrect.bottom),
+          Offset(rrect.left, rrect.bottom - rrect.blRadiusY))
+      ..lineTo(Offset(rrect.left, rrect.top + rrect.tlRadiusX))
+      ..quadTo(Offset(rrect.left, rrect.top),
+          Offset(rrect.left + rrect.tlRadiusX, rrect.top));
+  }
+
+  _add(Bezier bezier, Offset pn) {
+    _curves.add(bezier);
+    final bl = bezierLength(bezier);
+    _lens.add(bl);
+    _length += bl;
+    _p0 = pn;
+  }
+
+  lineTo(Offset p1) => _add(LinearBezier(_p0, p1), p1);
+
+  quadTo(Offset p1, Offset p2) => _add(QuadraticBezier(_p0, p1, p2), p2);
+
+  cubeTo(Offset p1, Offset p2, Offset p3) =>
+      _add(CubicBezier(_p0, p1, p2, p3), p3);
+
+  relativeLineTo(Offset p1) => lineTo(
+        p1 + _p0,
+      );
+
+  relativeQuadTo(Offset p1, Offset p2) => quadTo(
+        p1 + p0,
+        p1 + p2 + p0,
+      );
+
+  relativeCubeTo(Offset p1, Offset p2, Offset p3) => cubeTo(
+        p0 + p1,
+        p0 + p1 + p2,
+        p0 + p1 + p2 + p3,
+      );
+
+  Offset point(double t) {
+    if (_length == 0) return p0;
+    var distance = _length * t;
+    var index = 0;
+    while (index < _lens.length && distance > _lens[index]) {
+      distance -= _lens[index];
+      index++;
+    }
+    if (index == _lens.length) return _p0;
+    return _curves[index].point(distance / _lens[index]);
+  }
+}