MaskUtil.cpp Example File

 #include "MaskUtil.h"
 #include <zxing/common/IllegalArgumentException.h>
 #include <stdlib.h>

 namespace zxing {
 namespace qrcode {

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

 /**
    * 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.
    */
 int MaskUtil::applyMaskPenaltyRule1(const ByteMatrix& matrix)
 {
     return applyMaskPenaltyRule1Internal(matrix, true) + applyMaskPenaltyRule1Internal(matrix, false);
 }

 /**
    * 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.
    */
 int MaskUtil::applyMaskPenaltyRule2(const ByteMatrix& matrix)
 {
     int penalty = 0;
     const std::vector<std::vector<byte> >& array = matrix.getArray();
     int width = matrix.getWidth();
     int height = matrix.getHeight();
     for (int y = 0; y < height - 1; y++) {
         const std::vector<byte>& arrayY = array[y];
         for (int x = 0; x < width - 1; x++) {
             int value = arrayY[x];
             if (value == arrayY[x + 1] && value == array[y + 1][x] && value == array[y + 1][x + 1]) {
                 penalty++;
             }
         }
     }
     return N2 * penalty;
 }

 /**
    * Apply mask penalty rule 3 and return the penalty. Find consecutive runs of 1:1:3:1:1:4
    * starting with black, or 4:1:1:3:1:1 starting with white, and give penalty to them.  If we
    * find patterns like 000010111010000, we give penalty once.
    */
 int MaskUtil::applyMaskPenaltyRule3(const ByteMatrix& matrix)
 {
     int numPenalties = 0;
     const std::vector<std::vector<byte> >& array = matrix.getArray();
     int width = matrix.getWidth();
     int height = matrix.getHeight();
     for (int y = 0; y < height; y++) {
         for (int x = 0; x < width; x++) {
             const std::vector<byte>& arrayY = array[y];  // We can at least optimize this access
             if (x + 6 < width &&
                     arrayY[x] == 1 &&
                     arrayY[x +  1] == 0 &&
                     arrayY[x +  2] == 1 &&
                     arrayY[x +  3] == 1 &&
                     arrayY[x +  4] == 1 &&
                     arrayY[x +  5] == 0 &&
                     arrayY[x +  6] == 1 &&
                     (isWhiteHorizontal(arrayY, x - 4, x) || isWhiteHorizontal(arrayY, x + 7, x + 11))) {
                 numPenalties++;
             }
             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 &&
                     (isWhiteVertical(array, x, y - 4, y) || isWhiteVertical(array, x, y + 7, y + 11))) {
                 numPenalties++;
             }
         }
     }
     return numPenalties * N3;
 }

 bool MaskUtil::isWhiteHorizontal(const std::vector<byte>& rowArray, int from, int to)
 {
     from = std::max(from, 0);
     to = std::min(to, (int)rowArray.size());
     for (int i = from; i < to; i++) {
         if (rowArray[i] == 1) {
             return false;
         }
     }
     return true;
 }

 bool MaskUtil::isWhiteVertical(const std::vector<std::vector<byte> > &array, int col, int from, int to)
 {
     from = std::max(from, 0);
     to = std::min(to, (int)array.size());
     for (int i = from; i < to; i++) {
         if (array[i][col] == 1) {
             return false;
         }
     }
     return true;
 }

 /**
    * 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.
    */
 int MaskUtil::applyMaskPenaltyRule4(const ByteMatrix& matrix)
 {
     int numDarkCells = 0;
     const std::vector<std::vector<byte> >& array = matrix.getArray();
     int width = matrix.getWidth();
     int height = matrix.getHeight();
     for (int y = 0; y < height; y++) {
         const std::vector<byte>& arrayY = array[y];
         for (size_t x = 0; x < width; x++) {
             if (arrayY[x] == 1) {
                 numDarkCells++;
             }
         }
     }
     int numTotalCells = matrix.getHeight() * matrix.getWidth();
     int fivePercentVariances = abs(numDarkCells * 2 - numTotalCells) * 10 / numTotalCells;
     return fivePercentVariances * N4;
 }

 /**
    * Return the mask bit for "getMaskPattern" at "x" and "y". See 8.8 of JISX0510:2004 for mask
    * pattern conditions.
    */
 bool MaskUtil::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 = ((y / 2) + (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 IllegalArgumentException("Invalid mask pattern: " + maskPattern);
     }
     return intermediate == 0;
 }

 /**
    * Helper function for applyMaskPenaltyRule1. We need this for doing this calculation in both
    * vertical and horizontal orders respectively.
    */
 int MaskUtil::applyMaskPenaltyRule1Internal(const ByteMatrix& matrix, bool isHorizontal)
 {
     int penalty = 0;
     int iLimit = isHorizontal ? matrix.getHeight() : matrix.getWidth();
     int jLimit = isHorizontal ? matrix.getWidth() : matrix.getHeight();
     const std::vector<std::vector<byte> >& array = matrix.getArray();
     for (size_t 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;
 }

 }
 }