102 lines
3.3 KiB
Java
102 lines
3.3 KiB
Java
/*
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* Copyright (C) 2013 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 com.android.inputmethod.keyboard.internal;
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import com.android.inputmethod.annotations.UsedForTesting;
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import com.android.inputmethod.keyboard.internal.MatrixUtils.MatrixOperationFailedException;
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import android.util.Log;
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import java.util.Arrays;
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/**
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* Utilities to smooth coordinates. Currently, we calculate 3d least squares formula by using
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* Lagrangian smoothing
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*/
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@UsedForTesting
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public class SmoothingUtils {
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private static final String TAG = SmoothingUtils.class.getSimpleName();
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private static final boolean DEBUG = false;
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private SmoothingUtils() {
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// not allowed to instantiate publicly
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}
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/**
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* Find a most likely 3d least squares formula for specified coordinates.
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* "retval" should be a 1x4 size matrix.
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*/
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@UsedForTesting
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public static void get3DParameters(final float[] xs, final float[] ys,
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final float[][] retval) throws MatrixOperationFailedException {
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final int COEFF_COUNT = 4; // Coefficient count for 3d smoothing
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if (retval.length != COEFF_COUNT || retval[0].length != 1) {
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Log.d(TAG, "--- invalid length of 3d retval " + retval.length + ", "
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+ retval[0].length);
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return;
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}
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final int N = xs.length;
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// TODO: Never isntantiate the matrix
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final float[][] m0 = new float[COEFF_COUNT][COEFF_COUNT];
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final float[][] m0Inv = new float[COEFF_COUNT][COEFF_COUNT];
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final float[][] m1 = new float[COEFF_COUNT][N];
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final float[][] m2 = new float[N][1];
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// m0
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for (int i = 0; i < COEFF_COUNT; ++i) {
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Arrays.fill(m0[i], 0);
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for (int j = 0; j < COEFF_COUNT; ++j) {
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final int pow = i + j;
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for (int k = 0; k < N; ++k) {
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m0[i][j] += (float) Math.pow(xs[k], pow);
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}
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}
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}
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// m0Inv
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MatrixUtils.inverse(m0, m0Inv);
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if (DEBUG) {
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MatrixUtils.dump("m0-1", m0Inv);
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}
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// m1
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for (int i = 0; i < COEFF_COUNT; ++i) {
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for (int j = 0; j < N; ++j) {
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m1[i][j] = (i == 0) ? 1.0f : m1[i - 1][j] * xs[j];
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}
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}
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// m2
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for (int i = 0; i < N; ++i) {
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m2[i][0] = ys[i];
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}
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final float[][] m0Invxm1 = new float[COEFF_COUNT][N];
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if (DEBUG) {
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MatrixUtils.dump("a0", m0Inv);
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MatrixUtils.dump("a1", m1);
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}
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MatrixUtils.multiply(m0Inv, m1, m0Invxm1);
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if (DEBUG) {
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MatrixUtils.dump("a2", m0Invxm1);
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MatrixUtils.dump("a3", m2);
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}
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MatrixUtils.multiply(m0Invxm1, m2, retval);
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if (DEBUG) {
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MatrixUtils.dump("result", retval);
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}
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}
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}
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