Java tutorial
/* * * This file is part of the iText (R) project. Copyright (c) 1998-2019 iText Group NV * Authors: Kevin Day, Bruno Lowagie, Paulo Soares, et al. * * This program is free software; you can redistribute it and/or modify * it under the terms of the GNU Affero General Public License version 3 * as published by the Free Software Foundation with the addition of the * following permission added to Section 15 as permitted in Section 7(a): * FOR ANY PART OF THE COVERED WORK IN WHICH THE COPYRIGHT IS OWNED BY * ITEXT GROUP. ITEXT GROUP DISCLAIMS THE WARRANTY OF NON INFRINGEMENT * OF THIRD PARTY RIGHTS * * This program is distributed in the hope that it will be useful, but * WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY * or FITNESS FOR A PARTICULAR PURPOSE. * See the GNU Affero General Public License for more details. * You should have received a copy of the GNU Affero General Public License * along with this program; if not, see http://www.gnu.org/licenses or write to * the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, * Boston, MA, 02110-1301 USA, or download the license from the following URL: * http://itextpdf.com/terms-of-use/ * * The interactive user interfaces in modified source and object code versions * of this program must display Appropriate Legal Notices, as required under * Section 5 of the GNU Affero General Public License. * * In accordance with Section 7(b) of the GNU Affero General Public License, * a covered work must retain the producer line in every PDF that is created * or manipulated using iText. * * You can be released from the requirements of the license by purchasing * a commercial license. Buying such a license is mandatory as soon as you * develop commercial activities involving the iText software without * disclosing the source code of your own applications. * These activities include: offering paid services to customers as an ASP, * serving PDFs on the fly in a web application, shipping iText with a closed * source product. * * For more information, please contact iText Software Corp. at this * address: sales@itextpdf.com */ package com.itextpdf.text.pdf.parser; import java.util.Arrays; /** * Keeps all the values of a 3 by 3 matrix * and allows you to do some math with matrices. * * @since 2.1.4 */ public class Matrix { /** the row=1, col=1 position ('a') in the matrix. */ public static final int I11 = 0; /** the row=1, col=2 position ('b') in the matrix. */ public static final int I12 = 1; /** the row=1, col=3 position (always 0 for 2-D) in the matrix. */ public static final int I13 = 2; /** the row=2, col=1 position ('c') in the matrix. */ public static final int I21 = 3; /** the row=2, col=2 position ('d') in the matrix. */ public static final int I22 = 4; /** the row=2, col=3 position (always 0 for 2-D) in the matrix. */ public static final int I23 = 5; /** the row=3, col=1 ('e', or X translation) position in the matrix. */ public static final int I31 = 6; /** the row=3, col=2 ('f', or Y translation) position in the matrix. */ public static final int I32 = 7; /** the row=3, col=3 position (always 1 for 2-D) in the matrix. */ public static final int I33 = 8; /** the values inside the matrix (the identity matrix by default). * <p>For reference, the indeces are as follows:<p> * I11 I12 I13<p> * I21 I22 I23<p> * I31 I32 I33<p> */ private final float[] vals = new float[] { 1, 0, 0, 0, 1, 0, 0, 0, 1 }; /** * constructs a new Matrix with identity. */ public Matrix() { } /** * Constructs a matrix that represents translation * @param tx * @param ty */ public Matrix(float tx, float ty) { vals[I31] = tx; vals[I32] = ty; } /** * Creates a Matrix with 6 specified entries * @param a * @param b * @param c * @param d * @param e * @param f */ public Matrix(float a, float b, float c, float d, float e, float f) { vals[I11] = a; vals[I12] = b; vals[I13] = 0; vals[I21] = c; vals[I22] = d; vals[I23] = 0; vals[I31] = e; vals[I32] = f; vals[I33] = 1; } /** * Gets a specific value inside the matrix. * * <p>For reference, the indeces are as follows:<p> * I11 I12 I13<p> * I21 I22 I23<p> * I31 I32 I33<p> * * @param index an array index corresponding with a value inside the matrix * @return the value at that specific position. */ public float get(int index) { return vals[index]; } /** * multiplies this matrix by 'b' and returns the result * See http://en.wikipedia.org/wiki/Matrix_multiplication * @param by The matrix to multiply by * @return the resulting matrix */ public Matrix multiply(Matrix by) { Matrix rslt = new Matrix(); float[] a = vals; float[] b = by.vals; float[] c = rslt.vals; c[I11] = a[I11] * b[I11] + a[I12] * b[I21] + a[I13] * b[I31]; c[I12] = a[I11] * b[I12] + a[I12] * b[I22] + a[I13] * b[I32]; c[I13] = a[I11] * b[I13] + a[I12] * b[I23] + a[I13] * b[I33]; c[I21] = a[I21] * b[I11] + a[I22] * b[I21] + a[I23] * b[I31]; c[I22] = a[I21] * b[I12] + a[I22] * b[I22] + a[I23] * b[I32]; c[I23] = a[I21] * b[I13] + a[I22] * b[I23] + a[I23] * b[I33]; c[I31] = a[I31] * b[I11] + a[I32] * b[I21] + a[I33] * b[I31]; c[I32] = a[I31] * b[I12] + a[I32] * b[I22] + a[I33] * b[I32]; c[I33] = a[I31] * b[I13] + a[I32] * b[I23] + a[I33] * b[I33]; return rslt; } /** * Subtracts a matrix from this matrix and returns the results * @param arg the matrix to subtract from this matrix * @return a Matrix object */ public Matrix subtract(Matrix arg) { Matrix rslt = new Matrix(); float[] a = vals; float[] b = arg.vals; float[] c = rslt.vals; c[I11] = a[I11] - b[I11]; c[I12] = a[I12] - b[I12]; c[I13] = a[I13] - b[I13]; c[I21] = a[I21] - b[I21]; c[I22] = a[I22] - b[I22]; c[I23] = a[I23] - b[I23]; c[I31] = a[I31] - b[I31]; c[I32] = a[I32] - b[I32]; c[I33] = a[I33] - b[I33]; return rslt; } /** * Computes the determinant of the matrix. * @return the determinant of the matrix * @since 5.0.3 */ public float getDeterminant() { // ref http://en.wikipedia.org/wiki/Determinant // note that in PDF, I13 and I23 are always 0 and I33 is always 1 // so this could be simplified/faster return vals[I11] * vals[I22] * vals[I33] + vals[I12] * vals[I23] * vals[I31] + vals[I13] * vals[I21] * vals[I32] - vals[I11] * vals[I23] * vals[I32] - vals[I12] * vals[I21] * vals[I33] - vals[I13] * vals[I22] * vals[I31]; } /** * Checks equality of matrices. * @param obj the other Matrix that needs to be compared with this matrix. * @return true if both matrices are equal * @see java.lang.Object#equals(java.lang.Object) */ public boolean equals(Object obj) { if (!(obj instanceof Matrix)) return false; return Arrays.equals(vals, ((Matrix) obj).vals); } /** * Generates a hash code for this object. * @return the hash code of this object * @see java.lang.Object#hashCode() */ public int hashCode() { //return Arrays.hashCode(vals); // JDK 5 code, replaced with the following int result = 1; for (int i = 0; i < vals.length; i++) result = 31 * result + Float.floatToIntBits(vals[i]); return result; } /** * Generates a String representation of the matrix. * @return the values, delimited with tabs and newlines. * @see java.lang.Object#toString() */ public String toString() { return vals[I11] + "\t" + vals[I12] + "\t" + vals[I13] + "\n" + vals[I21] + "\t" + vals[I22] + "\t" + vals[I13] + "\n" + vals[I31] + "\t" + vals[I32] + "\t" + vals[I33]; } }