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

import 'package:fis_measure/interfaces/date_types/point.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,
  ) {
    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);
    }
  }
}

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);
    }
  }
}