fis_lib_measure/lib/process/primitives/utils/line.dart

import 'package:fis_measure/interfaces/date_types/point.dart';
import 'package:fis_measure/interfaces/date_types/vector.dart';

class LineUtils {
  // 计算两条直线是否有交点
  static DPoint? calculateIntersection(
    DPoint startA,
    DPoint endA,
    DPoint startB,
    DPoint endB,
  ) {
    return _getIntersectionPointCloneCSharp(startA, endA, startB, endB);
    // final lineA = _IntersectionTempLine.fromPoints(startA, endA);
    // final lineB = _IntersectionTempLine.fromPoints(startB, endB);

    // if (lineA.isVertical && lineB.isVertical) {
    //   // 两条直线都是垂直线，没有交点
    //   return null;
    // } else if (lineA.isVertical) {
    //   // 第一条直线是垂直线，交点的x坐标是第一条直线的x坐标
    //   return DPoint(
    //       lineA.intercept, lineB.slope * lineA.intercept + lineB.intercept);
    // } else if (lineB.isVertical) {
    //   // 第二条直线是垂直线，交点的x坐标是第二条直线的x坐标
    //   return DPoint(
    //       lineB.intercept, lineA.slope * lineB.intercept + lineA.intercept);
    // } else if (lineA.slope == lineB.slope) {
    //   // 斜率相同，直线平行或重合，没有交点
    //   return null;
    // } else {
    //   // 斜率不同，计算交点
    //   double x =
    //       (lineB.intercept - lineA.intercept) / (lineA.slope - lineB.slope);
    //   double y = lineA.slope * x + lineA.intercept;
    //   return DPoint(x, y);
    // }
  }

  static bool isPointOnLine(DPoint p1, DPoint p2, DPoint point) {
    // 计算向量v和w
    DVector v = p2 - p1;
    DVector w = point - p1;

    // 计算叉积和点积
    double crossProduct = v.x * w.y - v.y * w.x;
    double dotProduct = _dotVector(v, w);

    // 判断点是否在线上
    // 叉积接近0表示点在与线垂直的线上，点积在0到v的模的平方之间表示点在p1和p2之间
    return crossProduct.abs() < 1e-10 &&
        dotProduct >= 0 &&
        dotProduct <= _dotVector(v, v);
  }

  static double _dotVector(DVector a, DVector b) {
    return a.x * b.x + a.y * b.y;
  }

  static DPoint? _getIntersectionPointCloneCSharp(
      DPoint p1, DPoint p2, DPoint p3, DPoint p4) {
    double denom =
        (p4.x - p3.x) * (p2.y - p1.y) - (p2.x - p1.x) * (p4.y - p3.y);
    if (denom == 0) return null;
    double t1 =
        ((p3.x - p1.x) * (p3.y - p4.y) - (p3.y - p1.y) * (p3.x - p4.x)) / denom;
    return DPoint(p1.x + t1 * (p2.x - p1.x), p1.y + t1 * (p2.y - p1.y));
  }
}

class _IntersectionTempLine {
  final double slope;
  final double intercept;
  final bool isVertical;

  _IntersectionTempLine(this.slope, this.intercept, this.isVertical);

// 根据两个端点创建直线对象
  factory _IntersectionTempLine.fromPoints(DPoint p1, DPoint p2) {
    if (p1.x == p2.x) {
      // 垂直线
      return _IntersectionTempLine(double.nan, p1.x, true);
    } else {
      // 斜率
      double m = (p2.y - p1.y) / (p2.x - p1.x);
      // y轴截距
      double b = p1.y - m * p1.x;
      return _IntersectionTempLine(m, b, false);
    }
  }
}