perf: simplify long lists of points

lib/src/detect_shape.dart

@@ -6,10 +6,19 @@ import 'package:interactive_shape_recognition/src/shape.dart';
 import 'package:interactive_shape_recognition/src/utils.dart';
 
 /// Detects the shape of the given [points].
+/// 
+/// If [points] has more than [simplifyTo] points,
+/// it will be simplified to [simplifyTo] points
+/// to improve performance.
+/// You can disable this by setting [simplifyTo] to `null`.
 ///
 /// Returns a [DetectedShape] object with the detected shape
 /// ([DetectedShape.shape]) and some other information.
-DetectedShape detectShape(List<Offset> points) {
+DetectedShape detectShape(List<Offset> points, {int? simplifyTo = 500}) {
+  if (simplifyTo != null && points.length > simplifyTo) {
+    points = simplify(points, simplifyTo);
+  }
+
   final hull = convexHull(
     points,
     x: (Offset p) => p.dx,

lib/src/utils.dart

@@ -3,6 +3,26 @@ import 'dart:ui';
 
 import 'package:area_polygon/area_polygon.dart';
 
+List<Offset> simplify(List<Offset> points, int targetLength) {
+  if (points.length <= targetLength) {
+    return points;
+  }
+
+  final increment = points.length / targetLength;
+
+  final simplified = <Offset>[];
+  for (int i = 0; i < targetLength; i++) {
+    final index = (i * increment).round();
+    simplified.add(points[index]);
+  }
+
+  if (simplified.last != points.last) {
+    simplified.add(points.last);
+  }
+
+  return simplified;
+}
+
 double calcPerimeter(List<Offset> points) {
   double perimeter = 0;
   for (int i = 0; i < points.length - 1; i++) {