/*
* 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;
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> srowen@google.com (Sean Owen)
/// </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 from {@link com.google.zxing.common.BitMatrix#getBits()}
/// </param>
/// <param name="dimension">dimension of QR Code, represented by bits, being unmasked
/// </param>
internal abstract void unmaskBitMatrix(int[] bits, int dimension);
/// <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 (i + j) mod 2 == 0</summary>
private class DataMask000 : DataMask
{
private const int BITMASK = 0x55555555; // = 010101...
internal override void unmaskBitMatrix(int[] bits, int dimension)
{
// This one's easy. Because the dimension of BitMatrix is always odd,
// we can merely flip every other bit
int max = bits.Length;
for (int i = 0; i < max; i++)
{
bits[i] ^= BITMASK;
}
}
}
/// <summary> 001: mask bits for which i mod 2 == 0</summary>
private class DataMask001 : DataMask
{
internal override void unmaskBitMatrix(int[] bits, int dimension)
{
int bitMask = 0;
int count = 0;
int offset = 0;
for (int j = 0; j < dimension; j++)
{
for (int i = 0; i < dimension; i++)
{
if ((i & 0x01) == 0)
{
bitMask |= 1 << count;
}
if (++count == 32)
{
bits[offset++] ^= bitMask;
count = 0;
bitMask = 0;
}
}
}
bits[offset] ^= bitMask;
}
}
/// <summary> 010: mask bits for which j mod 3 == 0</summary>
private class DataMask010 : DataMask
{
internal override void unmaskBitMatrix(int[] bits, int dimension)
{
int bitMask = 0;
int count = 0;
int offset = 0;
for (int j = 0; j < dimension; j++)
{
bool columnMasked = j % 3 == 0;
for (int i = 0; i < dimension; i++)
{
if (columnMasked)
{
bitMask |= 1 << count;
}
if (++count == 32)
{
bits[offset++] ^= bitMask;
count = 0;
bitMask = 0;
}
}
}
bits[offset] ^= bitMask;
}
}
/// <summary> 011: mask bits for which (i + j) mod 3 == 0</summary>
private class DataMask011 : DataMask
{
internal override void unmaskBitMatrix(int[] bits, int dimension)
{
int bitMask = 0;
int count = 0;
int offset = 0;
for (int j = 0; j < dimension; j++)
{
for (int i = 0; i < dimension; i++)
{
if ((i + j) % 3 == 0)
{
bitMask |= 1 << count;
}
if (++count == 32)
{
bits[offset++] ^= bitMask;
count = 0;
bitMask = 0;
}
}
}
bits[offset] ^= bitMask;
}
}
/// <summary> 100: mask bits for which (i/2 + j/3) mod 2 == 0</summary>
private class DataMask100 : DataMask
{
internal override void unmaskBitMatrix(int[] bits, int dimension)
{
int bitMask = 0;
int count = 0;
int offset = 0;
for (int j = 0; j < dimension; j++)
{
int jComponentParity = (j / 3) & 0x01;
for (int i = 0; i < dimension; i++)
{
if (((i >> 1) & 0x01) == jComponentParity)
{
bitMask |= 1 << count;
}
if (++count == 32)
{
bits[offset++] ^= bitMask;
count = 0;
bitMask = 0;
}
}
}
bits[offset] ^= bitMask;
}
}
/// <summary> 101: mask bits for which ij mod 2 + ij mod 3 == 0</summary>
private class DataMask101 : DataMask
{
internal override void unmaskBitMatrix(int[] bits, int dimension)
{
int bitMask = 0;
int count = 0;
int offset = 0;
for (int j = 0; j < dimension; j++)
{
for (int i = 0; i < dimension; i++)
{
int product = i * j;
if (((product & 0x01) == 0) && product % 3 == 0)
{
bitMask |= 1 << count;
}
if (++count == 32)
{
bits[offset++] ^= bitMask;
count = 0;
bitMask = 0;
}
}
}
bits[offset] ^= bitMask;
}
}
/// <summary> 110: mask bits for which (ij mod 2 + ij mod 3) mod 2 == 0</summary>
private class DataMask110 : DataMask
{
internal override void unmaskBitMatrix(int[] bits, int dimension)
{
int bitMask = 0;
int count = 0;
int offset = 0;
for (int j = 0; j < dimension; j++)
{
for (int i = 0; i < dimension; i++)
{
int product = i * j;
if ((((product & 0x01) + product % 3) & 0x01) == 0)
{
bitMask |= 1 << count;
}
if (++count == 32)
{
bits[offset++] ^= bitMask;
count = 0;
bitMask = 0;
}
}
}
bits[offset] ^= bitMask;
}
}
/// <summary> 111: mask bits for which ((i+j)mod 2 + ij mod 3) mod 2 == 0</summary>
private class DataMask111 : DataMask
{
internal override void unmaskBitMatrix(int[] bits, int dimension)
{
int bitMask = 0;
int count = 0;
int offset = 0;
for (int j = 0; j < dimension; j++)
{
for (int i = 0; i < dimension; i++)
{
if (((((i + j) & 0x01) + (i * j) % 3) & 0x01) == 0)
{
bitMask |= 1 << count;
}
if (++count == 32)
{
bits[offset++] ^= bitMask;
count = 0;
bitMask = 0;
}
}
}
bits[offset] ^= bitMask;
}
}
}
}