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 {
27 // The mask penalty calculation is complicated. See Table 21 of JISX0510:2004 (p.45) for details.
28 // Basically it applies four rules and summate all penalties.
29 public static int CalculateMaskPenalty(final ByteMatrix matrix) {
31 penalty += ApplyMaskPenaltyRule1(matrix);
32 penalty += ApplyMaskPenaltyRule2(matrix);
33 penalty += ApplyMaskPenaltyRule3(matrix);
34 penalty += ApplyMaskPenaltyRule4(matrix);
38 // Apply mask penalty rule 1 and return the penalty. Find repetitive cells with the same color and
39 // give penalty to them. Example: 00000 or 11111.
40 public static int ApplyMaskPenaltyRule1(final ByteMatrix matrix) {
41 final int penalty = (ApplyMaskPenaltyRule1Internal(matrix, true) +
42 ApplyMaskPenaltyRule1Internal(matrix, false));
46 // Apply mask penalty rule 2 and return the penalty. Find 2x2 blocks with the same color and give
48 public static int ApplyMaskPenaltyRule2(final ByteMatrix matrix) {
50 byte[][] array = matrix.getArray();
51 int width = matrix.width();
52 int height = matrix.height();
53 for (int y = 0; y < height - 1; ++y) {
54 for (int x = 0; x < width - 1; ++x) {
55 int value = array[y][x];
56 if (value == array[y][x + 1] && value == array[y + 1][x] && value == array[y + 1][x + 1]) {
64 // Apply mask penalty rule 3 and return the penalty. Find consecutive cells of 00001011101 or
65 // 10111010000, and give penalty to them. If we find patterns like 000010111010000, we give
66 // penalties twice (i.e. 40 * 2).
67 public static int ApplyMaskPenaltyRule3(final ByteMatrix matrix) {
69 byte[][] array = matrix.getArray();
70 int width = matrix.width();
71 int height = matrix.height();
72 for (int y = 0; y < height; ++y) {
73 for (int x = 0; x < width; ++x) {
74 // Tried to simplify following conditions but failed.
77 array[y][x + 1] == 0 &&
78 array[y][x + 2] == 1 &&
79 array[y][x + 3] == 1 &&
80 array[y][x + 4] == 1 &&
81 array[y][x + 5] == 0 &&
82 array[y][x + 6] == 1 &&
84 array[y][x + 7] == 0 &&
85 array[y][x + 8] == 0 &&
86 array[y][x + 9] == 0 &&
87 array[y][x + 10] == 0) ||
89 array[y][x - 1] == 0 &&
90 array[y][x - 2] == 0 &&
91 array[y][x - 3] == 0 &&
92 array[y][x - 4] == 0))) {
97 array[y + 1][x] == 0 &&
98 array[y + 2][x] == 1 &&
99 array[y + 3][x] == 1 &&
100 array[y + 4][x] == 1 &&
101 array[y + 5][x] == 0 &&
102 array[y + 6][x] == 1 &&
104 array[y + 7][x] == 0 &&
105 array[y + 8][x] == 0 &&
106 array[y + 9][x] == 0 &&
107 array[y + 10][x] == 0) ||
109 array[y - 1][x] == 0 &&
110 array[y - 2][x] == 0 &&
111 array[y - 3][x] == 0 &&
112 array[y - 4][x] == 0))) {
120 // Apply mask penalty rule 4 and return the penalty. Calculate the ratio of dark cells and give
121 // penalty if the ratio is far from 50%. It gives 10 penalty for 5% distance. Examples:
129 public static int ApplyMaskPenaltyRule4(final ByteMatrix matrix) {
130 int num_dark_cells = 0;
131 byte[][] array = matrix.getArray();
132 int width = matrix.width();
133 int height = matrix.height();
134 for (int y = 0; y < height; ++y) {
135 for (int x = 0; x < width; ++x) {
136 if (array[y][x] == 1) {
141 final int num_total_cells = matrix.height() * matrix.width();
142 double dark_ratio = (double) num_dark_cells / num_total_cells;
143 final int penalty = Math.abs((int) (dark_ratio * 100 - 50)) / 5 * 10;
147 // Return the mask bit for "mask_pattern" at "x" and "y". See 8.8 of JISX0510:2004 for mask
148 // pattern conditions.
149 public static int GetDataMaskBit(final int mask_pattern, final int x, final int y) {
150 if (!QRCode.IsValidMaskPattern(mask_pattern)) {
151 throw new IllegalArgumentException("Invalid mask pattern");
153 switch (mask_pattern) {
155 return ((y + x) % 2 == 0) ? 1 : 0;
157 return (y % 2 == 0) ? 1 : 0;
159 return (x % 3 == 0) ? 1 : 0;
161 return ((y + x) % 3 == 0) ? 1 : 0;
163 return (((y / 2) + (x / 3)) % 2 == 0) ? 1 : 0;
165 return (((y * x) % 2) + ((y * x) % 3) == 0) ? 1 : 0;
167 return ((((y * x) % 2) + ((y * x) % 3)) % 2 == 0) ? 1 : 0;
169 return ((((y * x) % 3) + ((y + x) % 2)) % 2 == 0) ? 1 : 0;
171 throw new IllegalArgumentException("invalid mask pattern: " + mask_pattern);
174 // Helper function for ApplyMaskPenaltyRule1. We need this for doing this calculation in both
175 // vertical and horizontal orders respectively.
176 private static int ApplyMaskPenaltyRule1Internal(final ByteMatrix matrix, boolean is_horizontal) {
178 int num_same_bit_cells = 0;
181 // for (int i = 0; i < matrix.height(); ++i) {
182 // for (int j = 0; j < matrix.width(); ++j) {
183 // int bit = matrix.get(i, j);
185 // for (int i = 0; i < matrix.width(); ++i) {
186 // for (int j = 0; j < matrix.height(); ++j) {
187 // int bit = matrix.get(j, i);
188 final int i_limit = is_horizontal ? matrix.height() : matrix.width();
189 final int j_limit = is_horizontal ? matrix.width() : matrix.height();
190 byte[][] array = matrix.getArray();
191 for (int i = 0; i < i_limit; ++i) {
192 for (int j = 0; j < j_limit; ++j) {
193 final int bit = is_horizontal ? array[i][j] : array[j][i];
194 if (bit == prev_bit) {
195 num_same_bit_cells += 1;
196 // Found five repetitive cells with the same color (bit).
197 // We'll give penalty of 3.
198 if (num_same_bit_cells == 5) {
200 } else if (num_same_bit_cells > 5) {
201 // After five repetitive cells, we'll add the penalty one
206 num_same_bit_cells = 1; // Include the cell itself.
210 num_same_bit_cells = 0; // Clear at each row/column.