/**
* The $P Point-Cloud Recognizer (.NET Framework 4.0 C# version)
*
* Radu-Daniel Vatavu, Ph.D.
* University Stefan cel Mare of Suceava
* Suceava 720229, Romania
* vatavu@eed.usv.ro
*
* Lisa Anthony, Ph.D.
* UMBC
* Information Systems Department
* 1000 Hilltop Circle
* Baltimore, MD 21250
* lanthony@umbc.edu
*
* Jacob O. Wobbrock, Ph.D.
* The Information School
* University of Washington
* Seattle, WA 98195-2840
* wobbrock@uw.edu
*
* The academic publication for the $P recognizer, and what should be
* used to cite it, is:
*
* Vatavu, R.-D., Anthony, L. and Wobbrock, J.O. (2012).
* Gestures as point clouds: A $P recognizer for user interface
* prototypes. Proceedings of the ACM Int'l Conference on
* Multimodal Interfaces (ICMI '12). Santa Monica, California
* (October 22-26, 2012). New York: ACM Press, pp. 273-280.
*
* This software is distributed under the "New BSD License" agreement:
*
* Copyright (c) 2012, Radu-Daniel Vatavu, Lisa Anthony, and
* Jacob O. Wobbrock. All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions are met:
* * Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* * Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
* * Neither the names of the University Stefan cel Mare of Suceava,
* University of Washington, nor UMBC, nor the names of its contributors
* may be used to endorse or promote products derived from this software
* without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS
* IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
* THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
* PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL Radu-Daniel Vatavu OR Lisa Anthony
* OR Jacob O. Wobbrock BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
* EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT
* OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
* INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
* STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
* SUCH DAMAGE.
**/
using System;
namespace PDollarGestureRecognizer
{
/// <summary>
/// Implements a gesture as a cloud of points (i.e., an unordered set of points).
/// Gestures are normalized with respect to scale, translated to origin, and resampled into a fixed number of 32 points.
/// </summary>
public class Gesture
{
public Point[] Points = null; // gesture points (normalized)
public string Name = ""; // gesture class
private const int SAMPLING_RESOLUTION = 32;
/// <summary>
/// Constructs a gesture from an array of points
/// </summary>
/// <param name="points"></param>
public Gesture(Point[] points, string gestureName = "")
{
this.Name = gestureName;
// normalizes the array of points with respect to scale, origin, and number of points
this.Points = Scale(points);
this.Points = TranslateTo(Points, Centroid(Points));
this.Points = Resample(Points, SAMPLING_RESOLUTION);
}
#region gesture pre-processing steps: scale normalization, translation to origin, and resampling
/// <summary>
/// Performs scale normalization with shape preservation into [0..1]x[0..1]
/// </summary>
/// <param name="points"></param>
/// <returns></returns>
private Point[] Scale(Point[] points)
{
float minx = float.MaxValue, miny = float.MaxValue, maxx = float.MinValue, maxy = float.MinValue;
for (int i = 0; i < points.Length; i++)
{
if (minx > points[i].X) minx = points[i].X;
if (miny > points[i].Y) miny = points[i].Y;
if (maxx < points[i].X) maxx = points[i].X;
if (maxy < points[i].Y) maxy = points[i].Y;
}
Point[] newPoints = new Point[points.Length];
float scale = Math.Max(maxx - minx, maxy - miny);
for (int i = 0; i < points.Length; i++)
newPoints[i] = new Point((points[i].X - minx) / scale, (points[i].Y - miny) / scale, points[i].StrokeID);
return newPoints;
}
/// <summary>
/// Translates the array of points by p
/// </summary>
/// <param name="points"></param>
/// <param name="p"></param>
/// <returns></returns>
private Point[] TranslateTo(Point[] points, Point p)
{
Point[] newPoints = new Point[points.Length];
for (int i = 0; i < points.Length; i++)
newPoints[i] = new Point(points[i].X - p.X, points[i].Y - p.Y, points[i].StrokeID);
return newPoints;
}
/// <summary>
/// Computes the centroid for an array of points
/// </summary>
/// <param name="points"></param>
/// <returns></returns>
private Point Centroid(Point[] points)
{
float cx = 0, cy = 0;
for (int i = 0; i < points.Length; i++)
{
cx += points[i].X;
cy += points[i].Y;
}
return new Point(cx / points.Length, cy / points.Length, 0);
}
/// <summary>
/// Resamples the array of points into n equally-distanced points
/// </summary>
/// <param name="points"></param>
/// <param name="n"></param>
/// <returns></returns>
public Point[] Resample(Point[] points, int n)
{
Point[] newPoints = new Point[n];
newPoints[0] = new Point(points[0].X, points[0].Y, points[0].StrokeID);
int numPoints = 1;
float I = PathLength(points) / (n - 1); // computes interval length
float D = 0;
for (int i = 1; i < points.Length; i++)
{
if (points[i].StrokeID == points[i - 1].StrokeID)
{
float d = Geometry.EuclideanDistance(points[i - 1], points[i]);
if (D + d >= I)
{
Point firstPoint = points[i - 1];
while (D + d >= I)
{
// add interpolated point
float t = Math.Min(Math.Max((I - D) / d, 0.0f), 1.0f);
if (float.IsNaN(t)) t = 0.5f;
newPoints[numPoints++] = new Point(
(1.0f - t) * firstPoint.X + t * points[i].X,
(1.0f - t) * firstPoint.Y + t * points[i].Y,
points[i].StrokeID
);
// update partial length
d = D + d - I;
D = 0;
firstPoint = newPoints[numPoints - 1];
}
D = d;
}
else D += d;
}
}
if (numPoints == n - 1) // sometimes we fall a rounding-error short of adding the last point, so add it if so
newPoints[numPoints++] = new Point(points[points.Length - 1].X, points[points.Length - 1].Y, points[points.Length - 1].StrokeID);
return newPoints;
}
/// <summary>
/// Computes the path length for an array of points
/// </summary>
/// <param name="points"></param>
/// <returns></returns>
private float PathLength(Point[] points)
{
float length = 0;
for (int i = 1; i < points.Length; i++)
if (points[i].StrokeID == points[i - 1].StrokeID)
length += Geometry.EuclideanDistance(points[i - 1], points[i]);
return length;
}
#endregion
}
}