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/*
* 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.google.zxing.qrcode.decoder;
import com.google.zxing.common.BitMatrix;
/**
* <p>Encapsulates data masks for the data bits in a QR code, per ISO 18004:2006 6.8. Implementations
* of this class can un-mask a raw BitMatrix. For simplicity, they will unmask the entire BitMatrix,
* including areas used for finder patterns, timing patterns, etc. These areas should be unused
* after the point they are unmasked anyway.</p>
*
* <p>Note that the diagram in section 6.8.1 is misleading since it indicates that i is column position
* and j is row position. In fact, as the text says, i is row position and j is column position.</p>
*
* @author Sean Owen
*/
abstract class DataMask {
/**
* See ISO 18004:2006 6.8.1
*/
private static final DataMask[] DATA_MASKS = {
new DataMask000(),
new DataMask001(),
new DataMask010(),
new DataMask011(),
new DataMask100(),
new DataMask101(),
new DataMask110(),
new DataMask111(),
};
private DataMask() {
}
/**
* <p>Implementations of this method reverse the data masking process applied to a QR Code and
* make its bits ready to read.</p>
*
* @param bits representation of QR Code bits
* @param dimension dimension of QR Code, represented by bits, being unmasked
*/
final void unmaskBitMatrix(BitMatrix bits, int dimension) {
for (int i = 0; i < dimension; i++) {
for (int j = 0; j < dimension; j++) {
if (isMasked(i, j)) {
bits.flip(j, i);
}
}
}
}
abstract boolean isMasked(int i, int j);
/**
* @param reference a value between 0 and 7 indicating one of the eight possible
* data mask patterns a QR Code may use
* @return DataMask encapsulating the data mask pattern
*/
static DataMask forReference(int reference) {
if (reference < 0 || reference > 7) {
throw new IllegalArgumentException();
}
return DATA_MASKS[reference];
}
/**
* 000: mask bits for which (x + y) mod 2 == 0
*/
private static class DataMask000 extends DataMask {
boolean isMasked(int i, int j) {
return ((i + j) & 0x01) == 0;
}
}
/**
* 001: mask bits for which x mod 2 == 0
*/
private static class DataMask001 extends DataMask {
boolean isMasked(int i, int j) {
return (i & 0x01) == 0;
}
}
/**
* 010: mask bits for which y mod 3 == 0
*/
private static class DataMask010 extends DataMask {
boolean isMasked(int i, int j) {
return j % 3 == 0;
}
}
/**
* 011: mask bits for which (x + y) mod 3 == 0
*/
private static class DataMask011 extends DataMask {
boolean isMasked(int i, int j) {
return (i + j) % 3 == 0;
}
}
/**
* 100: mask bits for which (x/2 + y/3) mod 2 == 0
*/
private static class DataMask100 extends DataMask {
boolean isMasked(int i, int j) {
return (((i >>> 1) + (j /3)) & 0x01) == 0;
}
}
/**
* 101: mask bits for which xy mod 2 + xy mod 3 == 0
*/
private static class DataMask101 extends DataMask {
boolean isMasked(int i, int j) {
int temp = i * j;
return (temp & 0x01) + (temp % 3) == 0;
}
}
/**
* 110: mask bits for which (xy mod 2 + xy mod 3) mod 2 == 0
*/
private static class DataMask110 extends DataMask {
boolean isMasked(int i, int j) {
int temp = i * j;
return (((temp & 0x01) + (temp % 3)) & 0x01) == 0;
}
}
/**
* 111: mask bits for which ((x+y)mod 2 + xy mod 3) mod 2 == 0
*/
private static class DataMask111 extends DataMask {
boolean isMasked(int i, int j) {
return ((((i + j) & 0x01) + ((i * j) % 3)) & 0x01) == 0;
}
}
}
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