zxing/csharp/qrcode/encoder/MaskUtil.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 System.Text;
using com.google.zxing;
using com.google.zxing.common;
using com.google.zxing.qrcode.decoder;
using com.google.zxing.qrcode;

namespace com.google.zxing.qrcode.encoder
{

    public sealed class MaskUtil
    {
        private MaskUtil()
        {
            // do nothing
        }

        // 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.
        public static int applyMaskPenaltyRule1(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.
        public static int applyMaskPenaltyRule2(ByteMatrix matrix)
        {
            int penalty = 0;
            sbyte[][] array = matrix.getArray();
            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 += 3;
                    }
                }
            }
            return penalty;
        }

        // 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).
        public static int applyMaskPenaltyRule3(ByteMatrix matrix)
        {
            int penalty = 0;
            sbyte[][] array = matrix.getArray();
            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 += 40;
                    }
                    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 += 40;
                    }
                }
            }
            return penalty;
        }

        // 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. Examples:
        // -   0% => 100
        // -  40% =>  20
        // -  45% =>  10
        // -  50% =>   0
        // -  55% =>  10
        // -  55% =>  20
        // - 100% => 100
        public static int applyMaskPenaltyRule4(ByteMatrix matrix)
        {
            int numDarkCells = 0;
            sbyte[][] array = matrix.getArray();
            int width = matrix.width();
            int height = matrix.height();
            for (int y = 0; y < height; ++y)
            {
                for (int x = 0; x < width; ++x)
                {
                    if (array[y][x] == 1)
                    {
                        numDarkCells += 1;
                    }
                }
            }
            int numTotalCells = matrix.height() * matrix.width();
            double darkRatio = (double)numDarkCells / numTotalCells;
            return Math.Abs((int)(darkRatio * 100 - 50)) / 5 * 10;
        }

        // Return the mask bit for "getMaskPattern" at "x" and "y". See 8.8 of JISX0510:2004 for mask
        // pattern conditions.
        public static int getDataMaskBit(int maskPattern, int x, int y)
        {
            if (!QRCode.isValidMaskPattern(maskPattern))
            {
                throw new ArgumentException("Invalid mask pattern");
            }
            switch (maskPattern)
            {
                case 0:
                    return ((y + x) % 2 == 0) ? 1 : 0;
                case 1:
                    return (y % 2 == 0) ? 1 : 0;
                case 2:
                    return (x % 3 == 0) ? 1 : 0;
                case 3:
                    return ((y + x) % 3 == 0) ? 1 : 0;
                case 4:
                    return (((y / 2) + (x / 3)) % 2 == 0) ? 1 : 0;
                case 5:
                    return (((y * x) % 2) + ((y * x) % 3) == 0) ? 1 : 0;
                case 6:
                    return ((((y * x) % 2) + ((y * x) % 3)) % 2 == 0) ? 1 : 0;
                case 7:
                    return ((((y * x) % 3) + ((y + x) % 2)) % 2 == 0) ? 1 : 0;
            }
            throw new ArgumentException("invalid mask pattern: " + maskPattern);
        }

        // Helper function for applyMaskPenaltyRule1. We need this for doing this calculation in both
        // vertical and horizontal orders respectively.
        private static int applyMaskPenaltyRule1Internal(ByteMatrix matrix, bool isHorizontal)
        {
            int penalty = 0;
            int numSameBitCells = 0;
            int prevBit = -1;
            // Horizontal mode:
            //   for (int i = 0; i < matrix.height(); ++i) {
            //     for (int j = 0; j < matrix.width(); ++j) {
            //       int bit = matrix.get(i, j);
            // Vertical mode:
            //   for (int i = 0; i < matrix.width(); ++i) {
            //     for (int j = 0; j < matrix.height(); ++j) {
            //       int bit = matrix.get(j, i);
            int iLimit = isHorizontal ? matrix.height() : matrix.width();
            int jLimit = isHorizontal ? matrix.width() : matrix.height();
            sbyte[][] array = matrix.getArray();
            for (int i = 0; i < iLimit; ++i)
            {
                for (int j = 0; j < jLimit; ++j)
                {
                    int bit = isHorizontal ? array[i][j] : array[j][i];
                    if (bit == prevBit)
                    {
                        numSameBitCells += 1;
                        // Found five repetitive cells with the same color (bit).
                        // We'll give penalty of 3.
                        if (numSameBitCells == 5)
                        {
                            penalty += 3;
                        }
                        else if (numSameBitCells > 5)
                        {
                            // After five repetitive cells, we'll add the penalty one
                            // by one.
                            penalty += 1;
                        }
                    }
                    else
                    {
                        numSameBitCells = 1;  // Include the cell itself.
                        prevBit = bit;
                    }
                }
                numSameBitCells = 0;  // Clear at each row/column.
            }
            return penalty;
        }
    }
}