2 * Licensed under the Apache License, Version 2.0 (the "License");
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3 * you may not use this file except in compliance with the License.
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4 * You may obtain a copy of the License at
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6 * http://www.apache.org/licenses/LICENSE-2.0
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8 * Unless required by applicable law or agreed to in writing, software
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9 * distributed under the License is distributed on an "AS IS" BASIS,
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10 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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11 * See the License for the specific language governing permissions and
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12 * limitations under the License.
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16 namespace com.google.zxing.qrcode.decoder
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19 /// <summary> <p>Encapsulates data masks for the data bits in a QR code, per ISO 18004:2006 6.8. Implementations
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20 /// of this class can un-mask a raw BitMatrix. For simplicity, they will unmask the entire BitMatrix,
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21 /// including areas used for finder patterns, timing patterns, etc. These areas should be unused
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22 /// after the point they are unmasked anyway.</p>
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24 /// <p>Note that the diagram in section 6.8.1 is misleading since it indicates that i is column position
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25 /// 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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28 /// <author> srowen@google.com (Sean Owen)
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30 abstract class DataMask
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33 /// <summary> See ISO 18004:2006 6.8.1</summary>
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34 //UPGRADE_NOTE: Final was removed from the declaration of 'DATA_MASKS '. "ms-help://MS.VSCC.v80/dv_commoner/local/redirect.htm?index='!DefaultContextWindowIndex'&keyword='jlca1003'"
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35 private static readonly DataMask[] DATA_MASKS = new DataMask[] { new DataMask000(), new DataMask001(), new DataMask010(), new DataMask011(), new DataMask100(), new DataMask101(), new DataMask110(), new DataMask111() };
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41 /// <summary> <p>Implementations of this method reverse the data masking process applied to a QR Code and
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42 /// make its bits ready to read.</p>
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45 /// <param name="bits">representation of QR Code bits from {@link com.google.zxing.common.BitMatrix#getBits()}
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47 /// <param name="dimension">dimension of QR Code, represented by bits, being unmasked
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49 internal abstract void unmaskBitMatrix(int[] bits, int dimension);
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51 /// <param name="reference">a value between 0 and 7 indicating one of the eight possible
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52 /// data mask patterns a QR Code may use
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54 /// <returns> {@link DataMask} encapsulating the data mask pattern
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56 internal static DataMask forReference(int reference)
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58 if (reference < 0 || reference > 7)
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60 throw new System.ArgumentException();
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62 return DATA_MASKS[reference];
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65 /// <summary> 000: mask bits for which (i + j) mod 2 == 0</summary>
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66 private class DataMask000 : DataMask
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68 private const int BITMASK = 0x55555555; // = 010101...
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70 internal override void unmaskBitMatrix(int[] bits, int dimension)
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72 // This one's easy. Because the dimension of BitMatrix is always odd,
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73 // we can merely flip every other bit
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74 int max = bits.Length;
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75 for (int i = 0; i < max; i++)
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82 /// <summary> 001: mask bits for which i mod 2 == 0</summary>
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83 private class DataMask001 : DataMask
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85 internal override void unmaskBitMatrix(int[] bits, int dimension)
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90 for (int j = 0; j < dimension; j++)
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92 for (int i = 0; i < dimension; i++)
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94 if ((i & 0x01) == 0)
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96 bitMask |= 1 << count;
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100 bits[offset++] ^= bitMask;
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106 bits[offset] ^= bitMask;
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110 /// <summary> 010: mask bits for which j mod 3 == 0</summary>
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111 private class DataMask010 : DataMask
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113 internal override void unmaskBitMatrix(int[] bits, int dimension)
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118 for (int j = 0; j < dimension; j++)
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120 bool columnMasked = j % 3 == 0;
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121 for (int i = 0; i < dimension; i++)
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125 bitMask |= 1 << count;
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129 bits[offset++] ^= bitMask;
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135 bits[offset] ^= bitMask;
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139 /// <summary> 011: mask bits for which (i + j) mod 3 == 0</summary>
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140 private class DataMask011 : DataMask
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142 internal override void unmaskBitMatrix(int[] bits, int dimension)
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147 for (int j = 0; j < dimension; j++)
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149 for (int i = 0; i < dimension; i++)
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151 if ((i + j) % 3 == 0)
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153 bitMask |= 1 << count;
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157 bits[offset++] ^= bitMask;
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163 bits[offset] ^= bitMask;
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167 /// <summary> 100: mask bits for which (i/2 + j/3) mod 2 == 0</summary>
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168 private class DataMask100 : DataMask
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170 internal override void unmaskBitMatrix(int[] bits, int dimension)
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175 for (int j = 0; j < dimension; j++)
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177 int jComponentParity = (j / 3) & 0x01;
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178 for (int i = 0; i < dimension; i++)
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180 if (((i >> 1) & 0x01) == jComponentParity)
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182 bitMask |= 1 << count;
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186 bits[offset++] ^= bitMask;
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192 bits[offset] ^= bitMask;
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196 /// <summary> 101: mask bits for which ij mod 2 + ij mod 3 == 0</summary>
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197 private class DataMask101 : DataMask
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199 internal override void unmaskBitMatrix(int[] bits, int dimension)
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204 for (int j = 0; j < dimension; j++)
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206 for (int i = 0; i < dimension; i++)
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208 int product = i * j;
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209 if (((product & 0x01) == 0) && product % 3 == 0)
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211 bitMask |= 1 << count;
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215 bits[offset++] ^= bitMask;
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221 bits[offset] ^= bitMask;
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225 /// <summary> 110: mask bits for which (ij mod 2 + ij mod 3) mod 2 == 0</summary>
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226 private class DataMask110 : DataMask
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228 internal override void unmaskBitMatrix(int[] bits, int dimension)
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233 for (int j = 0; j < dimension; j++)
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235 for (int i = 0; i < dimension; i++)
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237 int product = i * j;
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238 if ((((product & 0x01) + product % 3) & 0x01) == 0)
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240 bitMask |= 1 << count;
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244 bits[offset++] ^= bitMask;
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250 bits[offset] ^= bitMask;
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254 /// <summary> 111: mask bits for which ((i+j)mod 2 + ij mod 3) mod 2 == 0</summary>
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255 private class DataMask111 : DataMask
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257 internal override void unmaskBitMatrix(int[] bits, int dimension)
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262 for (int j = 0; j < dimension; j++)
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264 for (int i = 0; i < dimension; i++)
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266 if (((((i + j) & 0x01) + (i * j) % 3) & 0x01) == 0)
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268 bitMask |= 1 << count;
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272 bits[offset++] ^= bitMask;
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278 bits[offset] ^= bitMask;
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