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/*
* Copyright (C) 2008-2009 The Android Open Source Project
*
* 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.
*/
package android.gesture;
import android.graphics.Matrix;
/**
* An instance represents a sample if the label is available or a query if the
* label is null.
*/
class Instance {
private static final int SEQUENCE_SAMPLE_SIZE = 16;
private static final int PATCH_SAMPLE_SIZE = 16;
private final static float[] ORIENTATIONS = {
0, 45, 90, 135, 180, -0, -45, -90, -135, -180
};
// the feature vector
final float[] vector;
// the label can be null
final String label;
// the id of the instance
final long id;
private Instance(long id, float[] sample, String sampleName) {
this.id = id;
vector = sample;
label = sampleName;
}
private void normalize() {
float[] sample = vector;
float sum = 0;
int size = sample.length;
for (int i = 0; i < size; i++) {
sum += sample[i] * sample[i];
}
float magnitude = (float) Math.sqrt(sum);
for (int i = 0; i < size; i++) {
sample[i] /= magnitude;
}
}
/**
* create a learning instance for a single stroke gesture
*
* @param gesture
* @param label
* @return the instance
*/
static Instance createInstance(int samplingType, Gesture gesture, String label) {
float[] pts;
Instance instance;
if (samplingType == GestureLibrary.SEQUENCE_SENSITIVE) {
pts = temporalSampler(samplingType, gesture);
instance = new Instance(gesture.getID(), pts, label);
instance.normalize();
} else {
pts = spatialSampler(gesture);
instance = new Instance(gesture.getID(), pts, label);
}
return instance;
}
private static float[] spatialSampler(Gesture gesture) {
return GestureUtilities.spatialSampling(gesture, PATCH_SAMPLE_SIZE);
}
private static float[] temporalSampler(int samplingType, Gesture gesture) {
float[] pts = GestureUtilities.temporalSampling(gesture.getStrokes().get(0),
SEQUENCE_SAMPLE_SIZE);
float[] center = GestureUtilities.computeCentroid(pts);
float orientation = (float) Math.atan2(pts[1] - center[1], pts[0] - center[0]);
orientation *= 180 / Math.PI;
float adjustment = -orientation;
if (samplingType == GestureLibrary.ORIENTATION_SENSITIVE) {
int count = ORIENTATIONS.length;
for (int i = 0; i < count; i++) {
float delta = ORIENTATIONS[i] - orientation;
if (Math.abs(delta) < Math.abs(adjustment)) {
adjustment = delta;
}
}
}
Matrix m = new Matrix();
m.setTranslate(-center[0], -center[1]);
m.postRotate(adjustment);
m.mapPoints(pts);
return pts;
}
}
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