2 * Copyright 2008 ZXing authors
4 * Licensed under the Apache License, Version 2.0 (the "License");
5 * you may not use this file except in compliance with the License.
6 * You may obtain a copy of the License at
8 * http://www.apache.org/licenses/LICENSE-2.0
10 * Unless required by applicable law or agreed to in writing, software
11 * distributed under the License is distributed on an "AS IS" BASIS,
12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13 * See the License for the specific language governing permissions and
14 * limitations under the License.
17 package com.google.zxing.qrcode.encoder;
19 import com.google.zxing.common.ByteMatrix;
22 * @author satorux@google.com (Satoru Takabayashi) - creator
23 * @author dswitkin@google.com (Daniel Switkin) - ported from C++
25 public final class MaskUtil {
31 // Apply mask penalty rule 1 and return the penalty. Find repetitive cells with the same color and
32 // give penalty to them. Example: 00000 or 11111.
33 public static int applyMaskPenaltyRule1(ByteMatrix matrix) {
34 return applyMaskPenaltyRule1Internal(matrix, true) + applyMaskPenaltyRule1Internal(matrix, false);
37 // Apply mask penalty rule 2 and return the penalty. Find 2x2 blocks with the same color and give
39 public static int applyMaskPenaltyRule2(ByteMatrix matrix) {
41 byte[][] array = matrix.getArray();
42 int width = matrix.width();
43 int height = matrix.height();
44 for (int y = 0; y < height - 1; ++y) {
45 for (int x = 0; x < width - 1; ++x) {
46 int value = array[y][x];
47 if (value == array[y][x + 1] && value == array[y + 1][x] && value == array[y + 1][x + 1]) {
55 // Apply mask penalty rule 3 and return the penalty. Find consecutive cells of 00001011101 or
56 // 10111010000, and give penalty to them. If we find patterns like 000010111010000, we give
57 // penalties twice (i.e. 40 * 2).
58 public static int applyMaskPenaltyRule3(ByteMatrix matrix) {
60 byte[][] array = matrix.getArray();
61 int width = matrix.width();
62 int height = matrix.height();
63 for (int y = 0; y < height; ++y) {
64 for (int x = 0; x < width; ++x) {
65 // Tried to simplify following conditions but failed.
68 array[y][x + 1] == 0 &&
69 array[y][x + 2] == 1 &&
70 array[y][x + 3] == 1 &&
71 array[y][x + 4] == 1 &&
72 array[y][x + 5] == 0 &&
73 array[y][x + 6] == 1 &&
75 array[y][x + 7] == 0 &&
76 array[y][x + 8] == 0 &&
77 array[y][x + 9] == 0 &&
78 array[y][x + 10] == 0) ||
80 array[y][x - 1] == 0 &&
81 array[y][x - 2] == 0 &&
82 array[y][x - 3] == 0 &&
83 array[y][x - 4] == 0))) {
88 array[y + 1][x] == 0 &&
89 array[y + 2][x] == 1 &&
90 array[y + 3][x] == 1 &&
91 array[y + 4][x] == 1 &&
92 array[y + 5][x] == 0 &&
93 array[y + 6][x] == 1 &&
95 array[y + 7][x] == 0 &&
96 array[y + 8][x] == 0 &&
97 array[y + 9][x] == 0 &&
98 array[y + 10][x] == 0) ||
100 array[y - 1][x] == 0 &&
101 array[y - 2][x] == 0 &&
102 array[y - 3][x] == 0 &&
103 array[y - 4][x] == 0))) {
111 // Apply mask penalty rule 4 and return the penalty. Calculate the ratio of dark cells and give
112 // penalty if the ratio is far from 50%. It gives 10 penalty for 5% distance. Examples:
120 public static int applyMaskPenaltyRule4(ByteMatrix matrix) {
121 int numDarkCells = 0;
122 byte[][] array = matrix.getArray();
123 int width = matrix.width();
124 int height = matrix.height();
125 for (int y = 0; y < height; ++y) {
126 for (int x = 0; x < width; ++x) {
127 if (array[y][x] == 1) {
132 int numTotalCells = matrix.height() * matrix.width();
133 double darkRatio = (double) numDarkCells / numTotalCells;
134 return Math.abs((int) (darkRatio * 100 - 50)) / 5 * 10;
137 // Return the mask bit for "getMaskPattern" at "x" and "y". See 8.8 of JISX0510:2004 for mask
138 // pattern conditions.
139 public static int getDataMaskBit(int maskPattern, int x, int y) {
140 if (!QRCode.isValidMaskPattern(maskPattern)) {
141 throw new IllegalArgumentException("Invalid mask pattern");
143 switch (maskPattern) {
145 return ((y + x) % 2 == 0) ? 1 : 0;
147 return (y % 2 == 0) ? 1 : 0;
149 return (x % 3 == 0) ? 1 : 0;
151 return ((y + x) % 3 == 0) ? 1 : 0;
153 return (((y / 2) + (x / 3)) % 2 == 0) ? 1 : 0;
155 return (((y * x) % 2) + ((y * x) % 3) == 0) ? 1 : 0;
157 return ((((y * x) % 2) + ((y * x) % 3)) % 2 == 0) ? 1 : 0;
159 return ((((y * x) % 3) + ((y + x) % 2)) % 2 == 0) ? 1 : 0;
161 throw new IllegalArgumentException("invalid mask pattern: " + maskPattern);
164 // Helper function for applyMaskPenaltyRule1. We need this for doing this calculation in both
165 // vertical and horizontal orders respectively.
166 private static int applyMaskPenaltyRule1Internal(ByteMatrix matrix, boolean isHorizontal) {
168 int numSameBitCells = 0;
171 // for (int i = 0; i < matrix.height(); ++i) {
172 // for (int j = 0; j < matrix.width(); ++j) {
173 // int bit = matrix.get(i, j);
175 // for (int i = 0; i < matrix.width(); ++i) {
176 // for (int j = 0; j < matrix.height(); ++j) {
177 // int bit = matrix.get(j, i);
178 int iLimit = isHorizontal ? matrix.height() : matrix.width();
179 int jLimit = isHorizontal ? matrix.width() : matrix.height();
180 byte[][] array = matrix.getArray();
181 for (int i = 0; i < iLimit; ++i) {
182 for (int j = 0; j < jLimit; ++j) {
183 int bit = isHorizontal ? array[i][j] : array[j][i];
184 if (bit == prevBit) {
185 numSameBitCells += 1;
186 // Found five repetitive cells with the same color (bit).
187 // We'll give penalty of 3.
188 if (numSameBitCells == 5) {
190 } else if (numSameBitCells > 5) {
191 // After five repetitive cells, we'll add the penalty one
196 numSameBitCells = 1; // Include the cell itself.
200 numSameBitCells = 0; // Clear at each row/column.