Android Open Source - Android-Gestures Gesture Engine

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The source code is released under:

Copyright (c) 2010, Michael Marner (michael@20papercups.net) All rights reserved. Redistribution and use in source and binary forms, with or without modification, are permitted provided that the fol...

Java Source Code

/*
 * Copyright (c) 2010, Michael Marner (michael@20papercups.net) 
 * All rights reserved./*from www.ja  v a2 s .c om*/
 * 
 * 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 name of the <organization> 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 <COPYRIGHT HOLDER> 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.
 */

package com.michaelmarner.gestures;

import java.util.*;

public class GestureEngine {

  /**
   * The number of points paths will be resized to.
   */
  private int pathFidelity;
  private int size;
  
  private LinkedList<Gesture> gestures;
  
  public GestureEngine() {
    gestures = new LinkedList<Gesture>();
    pathFidelity = 64;
    size = 2;
  }
  
  public void addGesture(Gesture p) {
    prepare(p);
    gestures.add(p);
  }

  public GestureMatch recognise(Gesture g) {
    if (gestures.size() == 0)
      throw new RuntimeException("Gesture list is empty!");
    prepare(g);
    
    float b = Integer.MAX_VALUE;
    
    GestureMatch bestMatch = new GestureMatch();
    
    for (Gesture template : gestures) {
    
      float d = distanceAtBestAngle(g, template, -45, 45, 2);
      if (d < b) {
        b = d;
        bestMatch.gesture = template;
      }
    }
    bestMatch.confidence = (float) (1 - b / 0.5 * Math.sqrt(size*size + size*size));
    return bestMatch;
  }
  
  private float distanceAtBestAngle(Gesture path, Gesture template, float thetaA, float thetaB, float deviation) {
    float magicNumber = (float) (0.5*(-1 + Math.sqrt(5)));

    float x1 = magicNumber*thetaA + (1-magicNumber)*thetaB;
    float f1 = distanceAtAngle(path, template, x1);
    float x2 = (1-magicNumber)*thetaA + magicNumber*thetaB;
    float f2 = distanceAtAngle(path, template, x2);

    while (Math.abs(thetaB - thetaA) > deviation)
    {
      if (f1 < f2)
      {
        thetaB = x2;
        x2 = x1;
        f2 = f1;
        x1 = magicNumber*thetaA + (1-magicNumber)*thetaB;
        f1 = distanceAtAngle(path, template, x1);
      }
      else
      {
        thetaA = x1;
        x1 = x2;
        f1 = f2;
        x2 = (1-magicNumber)*thetaA + magicNumber*thetaB;
        f2 = distanceAtAngle(path, template, x2);
      }
    }
    if (f1 < f2)
      return f1;
    return f2;
  }
  
  private float distanceAtAngle(Gesture path, Gesture template, float theta) {
    Gesture newPoints = new Gesture(path);
    newPoints.rotateBy(theta);
    return newPoints.distance(template);
  }
  
  
  private void prepare(Gesture p) {
    p.resample(pathFidelity);
    p.rotateToZero();
    p.scaleToSquare(size);
    p.translateToOrigin();
  }
  

}

Java Source Code List

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