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diff --git a/ink_stroke_modeler/internal/wobble_smoother.h b/ink_stroke_modeler/internal/wobble_smoother.h
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+/*
+ * Copyright 2022 Google LLC
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#ifndef INK_STROKE_MODELER_INTERNAL_WOBBLE_SMOOTHER_H_
+#define INK_STROKE_MODELER_INTERNAL_WOBBLE_SMOOTHER_H_
+
+#include <deque>
+
+#include "ink_stroke_modeler/params.h"
+#include "ink_stroke_modeler/types.h"
+
+namespace ink {
+namespace stroke_model {
+
+// This class smooths "wobble" in input positions from high-frequency noise. It
+// does so by maintaining a moving average of the positions, and interpolating
+// between the given input and the moving average based on how quickly it's
+// moving. When moving at a speed above the ceiling in the WobbleSmootherParams,
+// the result will be the unmodified input; when moving at a speed below the
+// floor, the result will be the moving average.
+class WobbleSmoother {
+ public:
+  void Reset(const WobbleSmootherParams &params, Vec2 position, Time time);
+
+  // Updates the average position and speed, and returns the smoothed position.
+  Vec2 Update(Vec2 position, Time time);
+
+ private:
+  struct Sample {
+    Vec2 position{0};
+    float speed{0};
+    Time time{0};
+  };
+  std::deque<Sample> samples_;
+  Vec2 position_sum_{0};
+  float speed_sum_{0};
+
+  WobbleSmootherParams params_;
+};
+
+}  // namespace stroke_model
+}  // namespace ink
+
+#endif  // INK_STROKE_MODELER_INTERNAL_WOBBLE_SMOOTHER_H_