114 lines
3.5 KiB
Java
114 lines
3.5 KiB
Java
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/*
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* Copyright (C) 2008-2009 The Android Open Source Project
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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package android.gesture;
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/**
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* An instance represents a sample if the label is available or a query if the
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* label is null.
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*/
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class Instance {
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private static final int SEQUENCE_SAMPLE_SIZE = 16;
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private static final int PATCH_SAMPLE_SIZE = 16;
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private final static float[] ORIENTATIONS = {
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0, (float) (Math.PI / 4), (float) (Math.PI / 2), (float) (Math.PI * 3 / 4),
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(float) Math.PI, -0, (float) (-Math.PI / 4), (float) (-Math.PI / 2),
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(float) (-Math.PI * 3 / 4), (float) -Math.PI
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};
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// the feature vector
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final float[] vector;
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// the label can be null
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final String label;
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// the id of the instance
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final long id;
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private Instance(long id, float[] sample, String sampleName) {
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this.id = id;
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vector = sample;
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label = sampleName;
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}
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private void normalize() {
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float[] sample = vector;
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float sum = 0;
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int size = sample.length;
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for (int i = 0; i < size; i++) {
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sum += sample[i] * sample[i];
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}
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float magnitude = (float)Math.sqrt(sum);
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for (int i = 0; i < size; i++) {
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sample[i] /= magnitude;
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}
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}
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/**
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* create a learning instance for a single stroke gesture
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*
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* @param gesture
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* @param label
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* @return the instance
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*/
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static Instance createInstance(int sequenceType, int orientationType, Gesture gesture, String label) {
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float[] pts;
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Instance instance;
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if (sequenceType == GestureStore.SEQUENCE_SENSITIVE) {
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pts = temporalSampler(orientationType, gesture);
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instance = new Instance(gesture.getID(), pts, label);
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instance.normalize();
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} else {
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pts = spatialSampler(gesture);
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instance = new Instance(gesture.getID(), pts, label);
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}
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return instance;
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}
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private static float[] spatialSampler(Gesture gesture) {
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return GestureUtils.spatialSampling(gesture, PATCH_SAMPLE_SIZE, false);
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}
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private static float[] temporalSampler(int orientationType, Gesture gesture) {
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float[] pts = GestureUtils.temporalSampling(gesture.getStrokes().get(0),
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SEQUENCE_SAMPLE_SIZE);
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float[] center = GestureUtils.computeCentroid(pts);
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float orientation = (float)Math.atan2(pts[1] - center[1], pts[0] - center[0]);
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float adjustment = -orientation;
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if (orientationType != GestureStore.ORIENTATION_INVARIANT) {
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int count = ORIENTATIONS.length;
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for (int i = 0; i < count; i++) {
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float delta = ORIENTATIONS[i] - orientation;
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if (Math.abs(delta) < Math.abs(adjustment)) {
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adjustment = delta;
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}
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}
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}
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GestureUtils.translate(pts, -center[0], -center[1]);
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GestureUtils.rotate(pts, adjustment);
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return pts;
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}
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}
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