zxing/csharp/qrcode/encoder/MaskUtil.cs

using System;

/*
 * Copyright 2008 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.encoder
{

	/// <summary>
	/// @author Satoru Takabayashi
	/// @author Daniel Switkin
	/// @author Sean Owen
	/// </summary>
	internal sealed class MaskUtil
	{

	  // Penalty weights from section 6.8.2.1
	  private const int N1 = 3;
	  private const int N2 = 3;
	  private const int N3 = 40;
	  private const int N4 = 10;

	  private MaskUtil()
	  {
		// do nothing
	  }

	  /// <summary>
	  /// Apply mask penalty rule 1 and return the penalty. Find repetitive cells with the same color and
	  /// give penalty to them. Example: 00000 or 11111.
	  /// </summary>
	  internal static int applyMaskPenaltyRule1(ByteMatrix matrix)
	  {
		return applyMaskPenaltyRule1Internal(matrix, true) + applyMaskPenaltyRule1Internal(matrix, false);
	  }

	  /// <summary>
	  /// Apply mask penalty rule 2 and return the penalty. Find 2x2 blocks with the same color and give
	  /// penalty to them. This is actually equivalent to the spec's rule, which is to find MxN blocks and give a
	  /// penalty proportional to (M-1)x(N-1), because this is the number of 2x2 blocks inside such a block.
	  /// </summary>
	  internal static int applyMaskPenaltyRule2(ByteMatrix matrix)
	  {
		int penalty = 0;
		sbyte[][] array = matrix.Array;
		int width = matrix.Width;
		int height = matrix.Height;
		for (int y = 0; y < height - 1; y++)
		{
		  for (int x = 0; x < width - 1; x++)
		  {
			int value = array[y][x];
			if (value == array[y][x + 1] && value == array[y + 1][x] && value == array[y + 1][x + 1])
			{
			  penalty++;
			}
		  }
		}
		return N2 * penalty;
	  }

	  /// <summary>
	  /// Apply mask penalty rule 3 and return the penalty. Find consecutive cells of 00001011101 or
	  /// 10111010000, and give penalty to them.  If we find patterns like 000010111010000, we give
	  /// penalties twice (i.e. 40 * 2).
	  /// </summary>
	  internal static int applyMaskPenaltyRule3(ByteMatrix matrix)
	  {
		int penalty = 0;
		sbyte[][] array = matrix.Array;
		int width = matrix.Width;
		int height = matrix.Height;
		for (int y = 0; y < height; y++)
		{
		  for (int x = 0; x < width; x++)
		  {
			// Tried to simplify following conditions but failed.
			if (x + 6 < width && array[y][x] == 1 && array[y][x + 1] == 0 && array[y][x + 2] == 1 && array[y][x + 3] == 1 && array[y][x + 4] == 1 && array[y][x + 5] == 0 && array[y][x + 6] == 1 && ((x + 10 < width && array[y][x + 7] == 0 && array[y][x + 8] == 0 && array[y][x + 9] == 0 && array[y][x + 10] == 0) || (x - 4 >= 0 && array[y][x - 1] == 0 && array[y][x - 2] == 0 && array[y][x - 3] == 0 && array[y][x - 4] == 0)))
			{
			  penalty += N3;
			}
			if (y + 6 < height && array[y][x] == 1 && array[y + 1][x] == 0 && array[y + 2][x] == 1 && array[y + 3][x] == 1 && array[y + 4][x] == 1 && array[y + 5][x] == 0 && array[y + 6][x] == 1 && ((y + 10 < height && array[y + 7][x] == 0 && array[y + 8][x] == 0 && array[y + 9][x] == 0 && array[y + 10][x] == 0) || (y - 4 >= 0 && array[y - 1][x] == 0 && array[y - 2][x] == 0 && array[y - 3][x] == 0 && array[y - 4][x] == 0)))
			{
			  penalty += N3;
			}
		  }
		}
		return penalty;
	  }

	  /// <summary>
	  /// Apply mask penalty rule 4 and return the penalty. Calculate the ratio of dark cells and give
	  /// penalty if the ratio is far from 50%. It gives 10 penalty for 5% distance.
	  /// </summary>
	  internal static int applyMaskPenaltyRule4(ByteMatrix matrix)
	  {
		int numDarkCells = 0;
		sbyte[][] array = matrix.Array;
		int width = matrix.Width;
		int height = matrix.Height;
		for (int y = 0; y < height; y++)
		{
		  sbyte[] arrayY = array[y];
		  for (int x = 0; x < width; x++)
		  {
			if (arrayY[x] == 1)
			{
			  numDarkCells++;
			}
		  }
		}
		int numTotalCells = matrix.Height * matrix.Width;
		double darkRatio = (double) numDarkCells / numTotalCells;
		int fivePercentVariances = (int)(Math.Abs(darkRatio - 0.5) * 20.0); // * 100.0 / 5.0
		return fivePercentVariances * N4;
	  }

	  /// <summary>
	  /// Return the mask bit for "getMaskPattern" at "x" and "y". See 8.8 of JISX0510:2004 for mask
	  /// pattern conditions.
	  /// </summary>
	  internal static bool getDataMaskBit(int maskPattern, int x, int y)
	  {
		int intermediate;
		int temp;
		switch (maskPattern)
		{
		  case 0:
			intermediate = (y + x) & 0x1;
			break;
		  case 1:
			intermediate = y & 0x1;
			break;
		  case 2:
			intermediate = x % 3;
			break;
		  case 3:
			intermediate = (y + x) % 3;
			break;
		  case 4:
			intermediate = (((int)((uint)y >> 1)) + (x / 3)) & 0x1;
			break;
		  case 5:
			temp = y * x;
			intermediate = (temp & 0x1) + (temp % 3);
			break;
		  case 6:
			temp = y * x;
			intermediate = ((temp & 0x1) + (temp % 3)) & 0x1;
			break;
		  case 7:
			temp = y * x;
			intermediate = ((temp % 3) + ((y + x) & 0x1)) & 0x1;
			break;
		  default:
			throw new System.ArgumentException("Invalid mask pattern: " + maskPattern);
		}
		return intermediate == 0;
	  }

	  /// <summary>
	  /// Helper function for applyMaskPenaltyRule1. We need this for doing this calculation in both
	  /// vertical and horizontal orders respectively.
	  /// </summary>
	  private static int applyMaskPenaltyRule1Internal(ByteMatrix matrix, bool isHorizontal)
	  {
		int penalty = 0;
		int iLimit = isHorizontal ? matrix.Height : matrix.Width;
		int jLimit = isHorizontal ? matrix.Width : matrix.Height;
		sbyte[][] array = matrix.Array;
		for (int i = 0; i < iLimit; i++)
		{
		  int numSameBitCells = 0;
		  int prevBit = -1;
		  for (int j = 0; j < jLimit; j++)
		  {
			int bit = isHorizontal ? array[i][j] : array[j][i];
			if (bit == prevBit)
			{
			  numSameBitCells++;
			}
			else
			{
			  if (numSameBitCells >= 5)
			  {
				penalty += N1 + (numSameBitCells - 5);
			  }
			  numSameBitCells = 1; // Include the cell itself.
			  prevBit = bit;
			}
		  }
		  if (numSameBitCells > 5)
		  {
			penalty += N1 + (numSameBitCells - 5);
		  }
		}
		return penalty;
	  }

	}

}