110 строки
3.3 KiB
C#
110 строки
3.3 KiB
C#
// Licensed to the .NET Foundation under one or more agreements.
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// The .NET Foundation licenses this file to you under the MIT license.
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// See the LICENSE file in the project root for more information.
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using System;
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using System.Collections.Generic;
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using Windows.Foundation;
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namespace Microsoft.Toolkit.Uwp.Input.GazeInteraction
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{
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/// <summary>
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/// Provides basic stats for eye gaze
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/// </summary>
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internal class GazeStats
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{
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/// <summary>
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/// Initializes a new instance of the <see cref="GazeStats"/> class.
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/// </summary>
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/// <param name="maxHistoryLen">Defines the size of the circular history for the calculations of stats</param>
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public GazeStats(int maxHistoryLen)
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{
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_maxHistoryLen = maxHistoryLen;
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_history = new List<Point>();
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}
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/// <summary>
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/// Resets the history, and stats
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/// </summary>
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public void Reset()
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{
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_sumX = 0;
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_sumY = 0;
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_sumSquaredX = 0;
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_sumSquaredY = 0;
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_history.Clear();
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}
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/// <summary>
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/// Adds a new item to the history
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/// </summary>
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/// <param name="x">X axis of the new point</param>
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/// <param name="y">Y axis of the new point</param>
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public void Update(float x, float y)
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{
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var pt = new Point(x, y);
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_history.Add(pt);
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if (_history.Count > _maxHistoryLen)
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{
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var oldest = _history[0];
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_history.RemoveAt(0);
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_sumX -= oldest.X;
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_sumY -= oldest.Y;
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_sumSquaredX -= oldest.X * oldest.X;
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_sumSquaredY -= oldest.Y * oldest.Y;
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}
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_sumX += x;
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_sumY += y;
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_sumSquaredX += x * x;
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_sumSquaredY += y * y;
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}
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/// <summary>
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/// Gets the mean of the history of points
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/// </summary>
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public Point Mean
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{
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get
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{
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var count = _history.Count;
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if (count < _maxHistoryLen)
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{
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return new Point(0.0f, 0.0f);
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}
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return new Point((float)_sumX / count, (float)_sumY / count);
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}
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}
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/// <summary>
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/// Gets the StandardDeviation of the items on the history => sqrt(Variance) = sqrt(E[X^2] – (E[X])^2)
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/// </summary>
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public Point StandardDeviation
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{
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get
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{
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var count = _history.Count;
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if (count < _maxHistoryLen)
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{
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return new Point(0.0f, 0.0f);
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}
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double meanX = _sumX / count;
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double meanY = _sumY / count;
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float stddevX = (float)Math.Sqrt((_sumSquaredX / count) - (meanX * meanX));
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float stddevY = (float)Math.Sqrt((_sumSquaredY / count) - (meanY * meanY));
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return new Point(stddevX, stddevY);
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}
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}
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private readonly int _maxHistoryLen;
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private readonly List<Point> _history;
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private double _sumX;
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private double _sumY;
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private double _sumSquaredX;
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private double _sumSquaredY;
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}
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} |