Java tutorial
/* * Copyright 2007 ZXing authors * * 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.itextpdf.text.pdf.qrcode; /** * <p>Represents a 2D matrix of bits. In function arguments below, and throughout the common * module, x is the column position, and y is the row position. The ordering is always x, y. * The origin is at the top-left.</p> * * <p>Internally the bits are represented in a 1-D array of 32-bit ints. However, each row begins * with a new int. This is done intentionally so that we can copy out a row into a BitArray very * efficiently.</p> * * <p>The ordering of bits is row-major. Within each int, the least significant bits are used first, * meaning they represent lower x values. This is compatible with BitArray's implementation.</p> * * @author Sean Owen * @author dswitkin@google.com (Daniel Switkin) * @since 5.0.2 */ public final class BitMatrix { // TODO: Just like BitArray, these need to be public so ProGuard can inline them. public final int width; public final int height; public final int rowSize; public final int[] bits; // A helper to construct a square matrix. public BitMatrix(int dimension) { this(dimension, dimension); } public BitMatrix(int width, int height) { if (width < 1 || height < 1) { throw new IllegalArgumentException("Both dimensions must be greater than 0"); } this.width = width; this.height = height; int rowSize = width >> 5; if ((width & 0x1f) != 0) { rowSize++; } this.rowSize = rowSize; bits = new int[rowSize * height]; } /** * <p>Gets the requested bit, where true means black.</p> * * @param x The horizontal component (i.e. which column) * @param y The vertical component (i.e. which row) * @return value of given bit in matrix */ public boolean get(int x, int y) { int offset = y * rowSize + (x >> 5); return ((bits[offset] >>> (x & 0x1f)) & 1) != 0; } /** * <p>Sets the given bit to true.</p> * * @param x The horizontal component (i.e. which column) * @param y The vertical component (i.e. which row) */ public void set(int x, int y) { int offset = y * rowSize + (x >> 5); bits[offset] |= 1 << (x & 0x1f); } /** * <p>Flips the given bit.</p> * * @param x The horizontal component (i.e. which column) * @param y The vertical component (i.e. which row) */ public void flip(int x, int y) { int offset = y * rowSize + (x >> 5); bits[offset] ^= 1 << (x & 0x1f); } /** * Clears all bits (sets to false). */ public void clear() { int max = bits.length; for (int i = 0; i < max; i++) { bits[i] = 0; } } /** * <p>Sets a square region of the bit matrix to true.</p> * * @param left The horizontal position to begin at (inclusive) * @param top The vertical position to begin at (inclusive) * @param width The width of the region * @param height The height of the region */ public void setRegion(int left, int top, int width, int height) { if (top < 0 || left < 0) { throw new IllegalArgumentException("Left and top must be nonnegative"); } if (height < 1 || width < 1) { throw new IllegalArgumentException("Height and width must be at least 1"); } int right = left + width; int bottom = top + height; if (bottom > this.height || right > this.width) { throw new IllegalArgumentException("The region must fit inside the matrix"); } for (int y = top; y < bottom; y++) { int offset = y * rowSize; for (int x = left; x < right; x++) { bits[offset + (x >> 5)] |= 1 << (x & 0x1f); } } } /** * A fast method to retrieve one row of data from the matrix as a BitArray. * * @param y The row to retrieve * @param row An optional caller-allocated BitArray, will be allocated if null or too small * @return The resulting BitArray - this reference should always be used even when passing * your own row */ public BitArray getRow(int y, BitArray row) { if (row == null || row.getSize() < width) { row = new BitArray(width); } int offset = y * rowSize; for (int x = 0; x < rowSize; x++) { row.setBulk(x << 5, bits[offset + x]); } return row; } /** * @return The width of the matrix */ public int getWidth() { return width; } /** * @return The height of the matrix */ public int getHeight() { return height; } /** * This method is for compatibility with older code. It's only logical to call if the matrix * is square, so I'm throwing if that's not the case. * * @return row/column dimension of this matrix */ public int getDimension() { if (width != height) { throw new RuntimeException("Can't call getDimension() on a non-square matrix"); } return width; } public String toString() { StringBuffer result = new StringBuffer(height * (width + 1)); for (int y = 0; y < height; y++) { for (int x = 0; x < width; x++) { result.append(get(x, y) ? "X " : " "); } result.append('\n'); } return result.toString(); } }