feat: add TransformedAnimation

Author: gonuit

lib/src/utils/transformed_animation.dart

@@ -0,0 +1,62 @@
+import 'package:flutter/animation.dart';
+
+/// An animation that transforms the value of another animation from a certain range to another.
+///
+/// This animation proxies the parent animation, but enforces the minimum and maximum values
+/// in the [toMin] and [toMax] range.
+///
+/// *From* values should be less than *max* values.
+///
+/// Example usage:
+/// ```dart
+/// final TransformedAnimation animation = TransformedAnimation(
+///   parent: parent,
+///   fromMin: 0.0,
+///   fromMax: 1.0,
+///   toMin: 0.0,
+///   toMax: 10.0,
+/// );
+/// ```
+/// Here `animation.value` will always be between 0.0 and 10.0, inclusive.
+class TransformedAnimation extends Animation<double> with AnimationWithParentMixin<double> {
+  /// Creates a transformed animation with an invariant range.
+  ///
+  /// The [parent] animation is the source of values for this animation.
+  /// The [fromMin] and [fromMax] parameters specify the range of the parent animation value that should be transformed.
+  /// The [toMin] and [toMax] parameters specify the range to which the animation value should be transformed.
+  ///
+  /// The constructor asserts that [fromMin] is less than [fromMax] and [toMin] is less than [toMax].
+  const TransformedAnimation({
+    required this.parent,
+    required this.fromMin,
+    required this.fromMax,
+    required this.toMin,
+    required this.toMax,
+  })  : assert(fromMin < fromMax, 'The fromMin value must be less than the fromMax value.'),
+        assert(toMin < toMax, 'The toMin value must be less than the toMax value.');
+
+  /// The animation that this clamped animation is based on.
+  @override
+  final Animation<double> parent;
+
+  /// The minimum value of the current range.
+  final double fromMin;
+
+  /// The maximum value of the current range.
+  final double fromMax;
+
+  /// The minimum value of the transformed range.
+  final double toMin;
+
+  /// The maximum value of the transformed range.
+  final double toMax;
+
+  /// Gets the current value of the parent animation transformed from the range [fromMin] -> [toMax] to [toMin] -> [toMax].
+  @override
+  double get value {
+    return (parent.value - fromMin) / (fromMax - fromMin) * (toMax - toMin) + toMin;
+  }
+
+  @override
+  String toString() => 'TransformedAnimation(min: $toMin, max: $toMax)';
+}

lib/src/utils/utils.dart

@@ -1 +1,2 @@
 export 'clamped_animation.dart';
+export 'transformed_animation.dart';