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.
*/
using System;
using BitMatrix = com.google.zxing.common.BitMatrix;
namespace com.google.zxing.qrcode.decoder
{
	
	/// <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>
	/// 
	/// </summary>
	/// <author>  Sean Owen
	/// </author>
	/// <author>www.Redivivus.in (suraj.supekar@redivivus.in) - Ported from ZXING Java Source 
	/// </author>
	abstract class DataMask
	{
		
		/// <summary> See ISO 18004:2006 6.8.1</summary>
		//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'"
		private static readonly DataMask[] DATA_MASKS = new DataMask[]{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> {@link DataMask} encapsulating the data mask pattern
		/// </returns>
		internal static 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 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 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 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 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 class DataMask100:DataMask
		{
			internal override bool isMasked(int i, int j)
			{
				return (((SupportClass.URShift(i, 1)) + (j / 3)) & 0x01) == 0;
			}
		}
		
		/// <summary> 101: mask bits for which xy mod 2 + xy mod 3 == 0</summary>
		private 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 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 class DataMask111:DataMask
		{
			internal override bool isMasked(int i, int j)
			{
				return ((((i + j) & 0x01) + ((i * j) % 3)) & 0x01) == 0;
			}
		}
	}
}