zxing/csharp/qrcode/decoder/DataMask.cs

/*
 * 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.
 */

namespace com.google.zxing.qrcode.decoder
{

	using BitMatrix = com.google.zxing.common.BitMatrix;

	/// <summary>
	/// <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
	/// </summary>
	internal abstract class DataMask
	{

	  /// <summary>
	  /// See ISO 18004:2006 6.8.1
	  /// </summary>
	  private static readonly DataMask[] DATA_MASKS = {new DataMask000(), new DataMask001(), new DataMask010(), new DataMask011(), new DataMask100(), new DataMask101(), new DataMask110(), new DataMask111()};

	  private DataMask()
	  {
	  }

	  /// <summary>
	  /// <p>Implementations of this method reverse the data masking process applied to a QR Code and
	  /// make its bits ready to read.</p>
	  /// </summary>
	  /// <param name="bits"> representation of QR Code bits </param>
	  /// <param name="dimension"> dimension of QR Code, represented by bits, being unmasked </param>
	  internal 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);
			}
		  }
		}
	  }

	  internal abstract bool isMasked(int i, int j);

	  /// <param name="reference"> a value between 0 and 7 indicating one of the eight possible
	  /// data mask patterns a QR Code may use </param>
	  /// <returns> DataMask encapsulating the data mask pattern </returns>
	  static internal DataMask forReference(int reference)
	  {
		if (reference < 0 || reference > 7)
		{
		  throw new System.ArgumentException();
		}
		return DATA_MASKS[reference];
	  }

	  /// <summary>
	  /// 000: mask bits for which (x + y) mod 2 == 0
	  /// </summary>
	  private sealed class DataMask000 : DataMask
	  {
		internal override bool isMasked(int i, int j)
		{
		  return ((i + j) & 0x01) == 0;
		}
	  }

	  /// <summary>
	  /// 001: mask bits for which x mod 2 == 0
	  /// </summary>
	  private sealed class DataMask001 : DataMask
	  {
		internal override bool isMasked(int i, int j)
		{
		  return (i & 0x01) == 0;
		}
	  }

	  /// <summary>
	  /// 010: mask bits for which y mod 3 == 0
	  /// </summary>
	  private sealed class DataMask010 : DataMask
	  {
		internal override bool isMasked(int i, int j)
		{
		  return j % 3 == 0;
		}
	  }

	  /// <summary>
	  /// 011: mask bits for which (x + y) mod 3 == 0
	  /// </summary>
	  private sealed class DataMask011 : DataMask
	  {
		internal override bool isMasked(int i, int j)
		{
		  return (i + j) % 3 == 0;
		}
	  }

	  /// <summary>
	  /// 100: mask bits for which (x/2 + y/3) mod 2 == 0
	  /// </summary>
	  private sealed class DataMask100 : DataMask
	  {
		internal override bool isMasked(int i, int j)
		{
		  return ((((int)((uint)i >> 1)) + (j / 3)) & 0x01) == 0;
		}
	  }

	  /// <summary>
	  /// 101: mask bits for which xy mod 2 + xy mod 3 == 0
	  /// </summary>
	  private sealed class DataMask101 : DataMask
	  {
		internal override bool isMasked(int i, int j)
		{
		  int temp = i * j;
		  return (temp & 0x01) + (temp % 3) == 0;
		}
	  }

	  /// <summary>
	  /// 110: mask bits for which (xy mod 2 + xy mod 3) mod 2 == 0
	  /// </summary>
	  private sealed class DataMask110 : DataMask
	  {
		internal override bool isMasked(int i, int j)
		{
		  int temp = i * j;
		  return (((temp & 0x01) + (temp % 3)) & 0x01) == 0;
		}
	  }

	  /// <summary>
	  /// 111: mask bits for which ((x+y)mod 2 + xy mod 3) mod 2 == 0
	  /// </summary>
	  private sealed class DataMask111 : DataMask
	  {
		internal override bool isMasked(int i, int j)
		{
		  return ((((i + j) & 0x01) + ((i * j) % 3)) & 0x01) == 0;
		}
	  }
	}

}