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authornicolasroard <nicolasroard@google.com>2013-06-19 11:36:46 -0700
committernicolasroard <nicolasroard@google.com>2013-06-19 11:36:46 -0700
commitd4702d8906274c64f7e7b08c7ecccf891e8a1a6e (patch)
tree257175d834faf93d75a06eef19271b0e4b64bf27 /src/com/android/gallery3d
parent8b0498d0cfed3e4cd5aa874760c222826bff64c6 (diff)
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Add a MatrixFit class
Change-Id: I67d2eb92fe5bbdff56ff50330c7eed48e7593f75
Diffstat (limited to 'src/com/android/gallery3d')
-rw-r--r--src/com/android/gallery3d/filtershow/tools/MatrixFit.java200
1 files changed, 200 insertions, 0 deletions
diff --git a/src/com/android/gallery3d/filtershow/tools/MatrixFit.java b/src/com/android/gallery3d/filtershow/tools/MatrixFit.java
new file mode 100644
index 000000000..3b815673c
--- /dev/null
+++ b/src/com/android/gallery3d/filtershow/tools/MatrixFit.java
@@ -0,0 +1,200 @@
+/*
+ * 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.gallery3d.filtershow.tools;
+
+import android.util.Log;
+
+public class MatrixFit {
+ // Simple implementation of a matrix fit in N dimensions.
+
+ private static final String LOGTAG = "MatrixFit";
+
+ private double[][] mMatrix;
+ private int mDimension;
+ private boolean mValid = false;
+ private static double sEPS = 1.0f/10000000000.0f;
+
+ public MatrixFit(double[][] from, double[][] to) {
+ mValid = fit(from, to);
+ }
+
+ public int getDimension() {
+ return mDimension;
+ }
+
+ public boolean isValid() {
+ return mValid;
+ }
+
+ public double[][] getMatrix() {
+ return mMatrix;
+ }
+
+ public boolean fit(double[][] from, double[][] to) {
+ if ((from.length != to.length) || (from.length < 1)) {
+ Log.e(LOGTAG, "from and to must be of same size");
+ return false;
+ }
+
+ mDimension = from[0].length;
+ mMatrix = new double[mDimension +1][mDimension + mDimension +1];
+
+ if (from.length < mDimension) {
+ Log.e(LOGTAG, "Too few points => under-determined system");
+ return false;
+ }
+
+ double[][] q = new double[from.length][mDimension];
+ for (int i = 0; i < from.length; i++) {
+ for (int j = 0; j < mDimension; j++) {
+ q[i][j] = from[i][j];
+ }
+ }
+
+ double[][] p = new double[to.length][mDimension];
+ for (int i = 0; i < to.length; i++) {
+ for (int j = 0; j < mDimension; j++) {
+ p[i][j] = to[i][j];
+ }
+ }
+
+ // Make an empty (dim) x (dim + 1) matrix and fill it
+ double[][] c = new double[mDimension+1][mDimension];
+ for (int j = 0; j < mDimension; j++) {
+ for (int k = 0; k < mDimension + 1; k++) {
+ for (int i = 0; i < q.length; i++) {
+ double qt = 1;
+ if (k < mDimension) {
+ qt = q[i][k];
+ }
+ c[k][j] += qt * p[i][j];
+ }
+ }
+ }
+
+ // Make an empty (dim+1) x (dim+1) matrix and fill it
+ double[][] Q = new double[mDimension+1][mDimension+1];
+ for (int qi = 0; qi < q.length; qi++) {
+ double[] qt = new double[mDimension + 1];
+ for (int i = 0; i < mDimension; i++) {
+ qt[i] = q[qi][i];
+ }
+ qt[mDimension] = 1;
+ for (int i = 0; i < mDimension + 1; i++) {
+ for (int j = 0; j < mDimension + 1; j++) {
+ Q[i][j] += qt[i] * qt[j];
+ }
+ }
+ }
+
+ // Use a gaussian elimination to solve the linear system
+ for (int i = 0; i < mDimension + 1; i++) {
+ for (int j = 0; j < mDimension + 1; j++) {
+ mMatrix[i][j] = Q[i][j];
+ }
+ for (int j = 0; j < mDimension; j++) {
+ mMatrix[i][mDimension + 1 + j] = c[i][j];
+ }
+ }
+ if (!gaussianElimination(mMatrix)) {
+ return false;
+ }
+ return true;
+ }
+
+ public double[] apply(double[] point) {
+ if (mDimension != point.length) {
+ return null;
+ }
+ double[] res = new double[mDimension];
+ for (int j = 0; j < mDimension; j++) {
+ for (int i = 0; i < mDimension; i++) {
+ res[j] += point[i] * mMatrix[i][j+ mDimension +1];
+ }
+ res[j] += mMatrix[mDimension][j+ mDimension +1];
+ }
+ return res;
+ }
+
+ public void printEquation() {
+ for (int j = 0; j < mDimension; j++) {
+ String str = "x" + j + "' = ";
+ for (int i = 0; i < mDimension; i++) {
+ str += "x" + i + " * " + mMatrix[i][j+mDimension+1] + " + ";
+ }
+ str += mMatrix[mDimension][j+mDimension+1];
+ Log.v(LOGTAG, str);
+ }
+ }
+
+ private void printMatrix(String name, double[][] matrix) {
+ Log.v(LOGTAG, "name: " + name);
+ for (int i = 0; i < matrix.length; i++) {
+ String str = "";
+ for (int j = 0; j < matrix[0].length; j++) {
+ str += "" + matrix[i][j] + " ";
+ }
+ Log.v(LOGTAG, str);
+ }
+ }
+
+ /*
+ * Transforms the given matrix into a row echelon matrix
+ */
+ private boolean gaussianElimination(double[][] m) {
+ int h = m.length;
+ int w = m[0].length;
+
+ for (int y = 0; y < h; y++) {
+ int maxrow = y;
+ for (int y2 = y + 1; y2 < h; y2++) { // Find max pivot
+ if (Math.abs(m[y2][y]) > Math.abs(m[maxrow][y])) {
+ maxrow = y2;
+ }
+ }
+ // swap
+ for (int i = 0; i < mDimension; i++) {
+ double t = m[y][i];
+ m[y][i] = m[maxrow][i];
+ m[maxrow][i] = t;
+ }
+
+ if (Math.abs(m[y][y]) <= sEPS) { // Singular Matrix
+ return false;
+ }
+ for (int y2 = y + 1; y2 < h; y2++) { // Eliminate column y
+ double c = m[y2][y] / m[y][y];
+ for (int x = y; x < w; x++) {
+ m[y2][x] -= m[y][x] * c;
+ }
+ }
+ }
+ for (int y = h -1; y > -1; y--) { // Back substitution
+ double c = m[y][y];
+ for (int y2 = 0; y2 < y; y2++) {
+ for (int x = w - 1; x > y - 1; x--) {
+ m[y2][x] -= m[y][x] * m[y2][y] / c;
+ }
+ }
+ m[y][y] /= c;
+ for (int x = h; x < w; x++) { // Normalize row y
+ m[y][x] /= c;
+ }
+ }
+ return true;
+ }
+}