fis_lib_measure/lib/process/calcuators/area.dart

import 'dart:math' as math;
import 'package:fis_measure/interfaces/date_types/point.dart';
import 'package:fis_measure/interfaces/process/calculators/output.dart';
import 'package:fis_measure/interfaces/process/items/measure_terms.dart';
import 'package:fis_measure/process/primitives/ellipse.dart';
import 'package:vid/us/vid_us_unit.dart';

import '../primitives/poyline.dart';
import 'calculator.dart';

class PolyLineAreaCal extends Calculator<PolyLine, double> {
  PolyLineAreaCal(PolyLine ref) : super(ref);

  @override
  void calculate() {
    if (ref.feature == null) return;

    // TODO:xxx
    final viewport = ref.feature!.hostVisualArea!.viewport!;
    final points =
        ref.feature!.innerPoints.map((e) => viewport.convert(e)).toList();

    double value = clacArea(points);
    final outputItem = createOutput(MeasureTerms.Area, value, VidUsUnit.cm2);
    final description = "${ref.description}: ${roundDouble(value)}cm²";
    outputItem.updateDescription(description: description);
    output = outputItem;
  }

  static double clacArea(List<DPoint> points) {
    if (points.isEmpty) {
      return 0;
    }

    double sum = 0;
    var ax = points[0].x;
    var ay = points[0].y;
    for (var i = 1; i < points.length - 1; i++) {
      var bx = points[i].x;
      var by = points[i].y;
      var cx = points[i + 1].x;
      var cy = points[i + 1].y;
      sum += ax * by - ay * bx + ay * cx - ax * cy + bx * cy - cx * by;
    }
    return (-sum / 2).abs();
  }
}