1 files changed, 102 insertions, 0 deletions
diff --git a/java/src/com/android/inputmethod/keyboard/internal/SmoothingUtils.java b/java/src/com/android/inputmethod/keyboard/internal/SmoothingUtils.java
new file mode 100644
index 000000000..e5665bcdd
--- /dev/null
+++ b/java/src/com/android/inputmethod/keyboard/internal/SmoothingUtils.java
@@ -0,0 +1,102 @@
+/*
+ * Copyright (C) 2013 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 com.android.inputmethod.keyboard.internal;
+
+import com.android.inputmethod.annotations.UsedForTesting;
+import com.android.inputmethod.keyboard.internal.MatrixUtils.MatrixOperationFailedException;
+
+import android.util.Log;
+
+import java.util.Arrays;
+
+/**
+ * Utilities to smooth coordinates. Currently, we calculate 3d least squares formula by using
+ * Lagrangian smoothing
+ */
+@UsedForTesting
+public class SmoothingUtils {
+    private static final String TAG = SmoothingUtils.class.getSimpleName();
+    private static final boolean DEBUG = false;
+
+    private SmoothingUtils() {
+        // not allowed to instantiate publicly
+    }
+
+    /**
+     * Find a most likely 3d least squares formula for specified coordinates.
+     * "retval" should be a 1x4 size matrix.
+     */
+    @UsedForTesting
+    public static void get3DParameters(final float[] xs, final float[] ys,
+            final float[][] retval) throws MatrixOperationFailedException {
+        final int COEFF_COUNT = 4; // Coefficient count for 3d smoothing
+        if (retval.length != COEFF_COUNT || retval[0].length != 1) {
+            Log.d(TAG, "--- invalid length of 3d retval " + retval.length + ", "
+                    + retval[0].length);
+            return;
+        }
+        final int N = xs.length;
+        // TODO: Never isntantiate the matrix
+        final float[][] m0 = new float[COEFF_COUNT][COEFF_COUNT];
+        final float[][] m0Inv = new float[COEFF_COUNT][COEFF_COUNT];
+        final float[][] m1 = new float[COEFF_COUNT][N];
+        final float[][] m2 = new float[N][1];
+
+        // m0
+        for (int i = 0; i < COEFF_COUNT; ++i) {
+            Arrays.fill(m0[i], 0);
+            for (int j = 0; j < COEFF_COUNT; ++j) {
+                final int pow = i + j;
+                for (int k = 0; k < N; ++k) {
+                    m0[i][j] += (float) Math.pow((double) xs[k], pow);
+                }
+            }
+        }
+        // m0Inv
+        MatrixUtils.inverse(m0, m0Inv);
+        if (DEBUG) {
+            MatrixUtils.dump("m0-1", m0Inv);
+        }
+
+        // m1
+        for (int i = 0; i < COEFF_COUNT; ++i) {
+            for (int j = 0; j < N; ++j) {
+                m1[i][j] = (i == 0) ? 1.0f : m1[i - 1][j] * xs[j];
+            }
+        }
+
+        // m2
+        for (int i = 0; i < N; ++i) {
+            m2[i][0] = ys[i];
+        }
+
+        final float[][] m0Invxm1 = new float[COEFF_COUNT][N];
+        if (DEBUG) {
+            MatrixUtils.dump("a0", m0Inv);
+            MatrixUtils.dump("a1", m1);
+        }
+        MatrixUtils.multiply(m0Inv, m1, m0Invxm1);
+        if (DEBUG) {
+            MatrixUtils.dump("a2", m0Invxm1);
+            MatrixUtils.dump("a3", m2);
+        }
+        MatrixUtils.multiply(m0Invxm1, m2, retval);
+        if (DEBUG) {
+            MatrixUtils.dump("result", retval);
+        }
+    }
+}