1 files changed, 155 insertions, 0 deletions
diff --git a/libraries/zxing/src/com/google/zxing/qrcode/decoder/DataMask.java b/libraries/zxing/src/com/google/zxing/qrcode/decoder/DataMask.java
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index 000000000..d29dbd47f
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+++ b/libraries/zxing/src/com/google/zxing/qrcode/decoder/DataMask.java
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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;
+    }
+  }
+}