Instance.java revision 436466d75edb5f6fd848504d998f244426ea5a09 
1/*
2 * Copyright (C) 2008-2009 The Android Open Source Project
3 *
4 * Licensed under the Apache License, Version 2.0 (the "License");
5 * you may not use this file except in compliance with the License.
6 * You may obtain a copy of the License at
7 *
8 *      http://www.apache.org/licenses/LICENSE-2.0
9 *
10 * Unless required by applicable law or agreed to in writing, software
11 * distributed under the License is distributed on an "AS IS" BASIS,
12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13 * See the License for the specific language governing permissions and
14 * limitations under the License.
15 */
16
17package android.gesture;
18
19import android.graphics.Matrix;
20
21/**
22 * An instance represents a sample if the label is available or a query if the
23 * label is null.
24 */
25class Instance {
26    private static final int SEQUENCE_SAMPLE_SIZE = 16;
27
28    private static final int PATCH_SAMPLE_SIZE = 16;
29
30    private final static float[] ORIENTATIONS = {
31            0, 45, 90, 135, 180, -0, -45, -90, -135, -180
32    };
33
34    // the feature vector
35    final float[] vector;
36
37    // the label can be null
38    final String label;
39
40    // the id of the instance
41    final long id;
42
43    private Instance(long id, float[] sample, String sampleName) {
44        this.id = id;
45        vector = sample;
46        label = sampleName;
47    }
48
49    private void normalize() {
50        float[] sample = vector;
51        float sum = 0;
52
53        int size = sample.length;
54        for (int i = 0; i < size; i++) {
55            sum += sample[i] * sample[i];
56        }
57
58        float magnitude = (float) Math.sqrt(sum);
59        for (int i = 0; i < size; i++) {
60            sample[i] /= magnitude;
61        }
62    }
63
64    /**
65     * create a learning instance for a single stroke gesture
66     *
67     * @param gesture
68     * @param label
69     * @return the instance
70     */
71    static Instance createInstance(int samplingType, Gesture gesture, String label) {
72        float[] pts;
73        Instance instance;
74        if (samplingType == GestureLibrary.SEQUENCE_SENSITIVE) {
75            pts = temporalSampler(samplingType, gesture);
76            instance = new Instance(gesture.getID(), pts, label);
77            instance.normalize();
78        } else {
79            pts = spatialSampler(gesture);
80            instance = new Instance(gesture.getID(), pts, label);
81        }
82        return instance;
83    }
84
85    private static float[] spatialSampler(Gesture gesture) {
86        return GestureUtilities.spatialSampling(gesture, PATCH_SAMPLE_SIZE);
87    }
88
89    private static float[] temporalSampler(int samplingType, Gesture gesture) {
90        float[] pts = GestureUtilities.temporalSampling(gesture.getStrokes().get(0),
91                SEQUENCE_SAMPLE_SIZE);
92        float[] center = GestureUtilities.computeCentroid(pts);
93        float orientation = (float) Math.atan2(pts[1] - center[1], pts[0] - center[0]);
94        orientation *= 180 / Math.PI;
95
96        float adjustment = -orientation;
97        if (samplingType == GestureLibrary.ORIENTATION_SENSITIVE) {
98            int count = ORIENTATIONS.length;
99            for (int i = 0; i < count; i++) {
100                float delta = ORIENTATIONS[i] - orientation;
101                if (Math.abs(delta) < Math.abs(adjustment)) {
102                    adjustment = delta;
103                }
104            }
105        }
106
107        Matrix m = new Matrix();
108        m.setTranslate(-center[0], -center[1]);
109        m.postRotate(adjustment);
110        m.mapPoints(pts);
111
112        return pts;
113    }
114
115}
116