2 * Copyright 2007 ZXing authors
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4 * Licensed under the Apache License, Version 2.0 (the "License");
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5 * you may not use this file except in compliance with the License.
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6 * You may obtain a copy of the License at
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8 * http://www.apache.org/licenses/LICENSE-2.0
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10 * Unless required by applicable law or agreed to in writing, software
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11 * distributed under the License is distributed on an "AS IS" BASIS,
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12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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13 * See the License for the specific language governing permissions and
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14 * limitations under the License.
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17 package com.google.zxing.qrcode.decoder;
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19 import com.google.zxing.common.BitMatrix;
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22 * <p>Encapsulates data masks for the data bits in a QR code, per ISO 18004:2006 6.8. Implementations
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23 * of this class can un-mask a raw BitMatrix. For simplicity, they will unmask the entire BitMatrix,
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24 * including areas used for finder patterns, timing patterns, etc. These areas should be unused
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25 * after the point they are unmasked anyway.</p>
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27 * <p>Note that the diagram in section 6.8.1 is misleading since it indicates that i is column position
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28 * and j is row position. In fact, as the text says, i is row position and j is column position.</p>
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32 abstract class DataMask {
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35 * See ISO 18004:2006 6.8.1
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37 private static final DataMask[] DATA_MASKS = {
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48 private DataMask() {
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52 * <p>Implementations of this method reverse the data masking process applied to a QR Code and
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53 * make its bits ready to read.</p>
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55 * @param bits representation of QR Code bits
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56 * @param dimension dimension of QR Code, represented by bits, being unmasked
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58 final void unmaskBitMatrix(BitMatrix bits, int dimension) {
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59 for (int i = 0; i < dimension; i++) {
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60 for (int j = 0; j < dimension; j++) {
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61 if (isMasked(i, j)) {
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68 abstract boolean isMasked(int i, int j);
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71 * @param reference a value between 0 and 7 indicating one of the eight possible
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72 * data mask patterns a QR Code may use
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73 * @return {@link DataMask} encapsulating the data mask pattern
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75 static DataMask forReference(int reference) {
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76 if (reference < 0 || reference > 7) {
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77 throw new IllegalArgumentException();
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79 return DATA_MASKS[reference];
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83 * 000: mask bits for which (x + y) mod 2 == 0
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85 private static class DataMask000 extends DataMask {
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86 boolean isMasked(int i, int j) {
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87 return ((i + j) & 0x01) == 0;
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92 * 001: mask bits for which x mod 2 == 0
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94 private static class DataMask001 extends DataMask {
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95 boolean isMasked(int i, int j) {
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96 return (i & 0x01) == 0;
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101 * 010: mask bits for which y mod 3 == 0
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103 private static class DataMask010 extends DataMask {
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104 boolean isMasked(int i, int j) {
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110 * 011: mask bits for which (x + y) mod 3 == 0
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112 private static class DataMask011 extends DataMask {
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113 boolean isMasked(int i, int j) {
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114 return (i + j) % 3 == 0;
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119 * 100: mask bits for which (x/2 + y/3) mod 2 == 0
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121 private static class DataMask100 extends DataMask {
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122 boolean isMasked(int i, int j) {
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123 return (((i >>> 1) + (j /3)) & 0x01) == 0;
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128 * 101: mask bits for which xy mod 2 + xy mod 3 == 0
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130 private static class DataMask101 extends DataMask {
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131 boolean isMasked(int i, int j) {
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133 return (temp & 0x01) + (temp % 3) == 0;
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138 * 110: mask bits for which (xy mod 2 + xy mod 3) mod 2 == 0
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140 private static class DataMask110 extends DataMask {
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141 boolean isMasked(int i, int j) {
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143 return (((temp & 0x01) + (temp % 3)) & 0x01) == 0;
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148 * 111: mask bits for which ((x+y)mod 2 + xy mod 3) mod 2 == 0
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150 private static class DataMask111 extends DataMask {
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151 boolean isMasked(int i, int j) {
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152 return ((((i + j) & 0x01) + ((i * j) % 3)) & 0x01) == 0;
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