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;
20 * @author satorux@google.com (Satoru Takabayashi) - creator
21 * @author dswitkin@google.com (Daniel Switkin) - ported from C++
23 public final class MaskUtil {
25 // The mask penalty calculation is complicated. See Table 21 of
26 // JISX0510:2004 (p.45) for details. Basically it applies four
27 // rules and summate all penalties.
28 public static int CalculateMaskPenalty(final Matrix matrix) {
30 penalty += ApplyMaskPenaltyRule1(matrix);
31 penalty += ApplyMaskPenaltyRule2(matrix);
32 penalty += ApplyMaskPenaltyRule3(matrix);
33 penalty += ApplyMaskPenaltyRule4(matrix);
37 // Apply mask penalty rule 1 and return the penalty.
38 // Find repetitive cells with the same color and give penalty to
39 // them. Example: 00000 or 11111.
40 public static int ApplyMaskPenaltyRule1(final Matrix matrix) {
41 final int penalty = (ApplyMaskPenaltyRule1Internal(matrix, true) +
42 ApplyMaskPenaltyRule1Internal(matrix, false));
43 Debug.LOG_INFO("\tApplyMaskPenaltyRule1: " + penalty);
47 // Apply mask penalty rule 2 and return the penalty.
48 // Find 2x2 blocks with the same color and give penalty to them.
50 // JAVAPORT: Consider using Matrix.getArray() instead.
51 public static int ApplyMaskPenaltyRule2(final Matrix matrix) {
53 for (int y = 0; y < matrix.height() - 1; ++y) {
54 for (int x = 0; x < matrix.width() - 1; ++x) {
55 int value = matrix.get(y, x);
56 if (value == matrix.get(y + 0, x + 1) &&
57 value == matrix.get(y + 1, x + 0) &&
58 value == matrix.get(y + 1, x + 1)) {
63 Debug.LOG_INFO("\tApplyMaskPenaltyRule2: " + penalty);
67 // Apply mask penalty rule 3 and return the penalty.
68 // Find consecutive cells of 00001011101 or 10111010000, and give
69 // penalty to them. If we find patterns like 000010111010000, we give
70 // penalties twice (i.e. 40 * 2).
72 // JAVAPORT: This many calls to Matrix.get() looks expensive. We should profile and consider
73 // adding a byte[][] Matrix.getArray() method, then using that array locally.
74 public static int ApplyMaskPenaltyRule3(final Matrix matrix) {
76 for (int y = 0; y < matrix.height(); ++y) {
77 for (int x = 0; x < matrix.width(); ++x) {
78 // Tried to simplify following conditions but failed.
79 if (x + 6 < matrix.width() &&
80 matrix.get(y, x + 0) == 1 &&
81 matrix.get(y, x + 1) == 0 &&
82 matrix.get(y, x + 2) == 1 &&
83 matrix.get(y, x + 3) == 1 &&
84 matrix.get(y, x + 4) == 1 &&
85 matrix.get(y, x + 5) == 0 &&
86 matrix.get(y, x + 6) == 1 &&
87 ((x + 10 < matrix.width() &&
88 matrix.get(y, x + 7) == 0 &&
89 matrix.get(y, x + 8) == 0 &&
90 matrix.get(y, x + 9) == 0 &&
91 matrix.get(y, x + 10) == 0) ||
93 matrix.get(y, x - 1) == 0 &&
94 matrix.get(y, x - 2) == 0 &&
95 matrix.get(y, x - 3) == 0 &&
96 matrix.get(y, x - 4) == 0))) {
99 if (y + 6 < matrix.height() &&
100 matrix.get(y + 0, x) == 1 &&
101 matrix.get(y + 1, x) == 0 &&
102 matrix.get(y + 2, x) == 1 &&
103 matrix.get(y + 3, x) == 1 &&
104 matrix.get(y + 4, x) == 1 &&
105 matrix.get(y + 5, x) == 0 &&
106 matrix.get(y + 6, x) == 1 &&
107 ((y + 10 < matrix.height() &&
108 matrix.get(y + 7, x) == 0 &&
109 matrix.get(y + 8, x) == 0 &&
110 matrix.get(y + 9, x) == 0 &&
111 matrix.get(y + 10, x) == 0) ||
113 matrix.get(y - 1, x) == 0 &&
114 matrix.get(y - 2, x) == 0 &&
115 matrix.get(y - 3, x) == 0 &&
116 matrix.get(y - 4, x) == 0))) {
121 Debug.LOG_INFO("\tApplyMaskPenaltyRule3: " + penalty);
125 // Apply mask penalty rule 4 and return the penalty.
126 // Calculate the ratio of dark cells and give penalty if the ratio
127 // is far from 50%. It gives 10 penalty for 5% distance.
136 public static int ApplyMaskPenaltyRule4(final Matrix matrix) {
137 int num_dark_cells = 0;
138 for (int y = 0; y < matrix.height(); ++y) {
139 for (int x = 0; x < matrix.width(); ++x) {
140 if (matrix.get(y, x) == 1) {
145 final int num_total_cells = matrix.height() * matrix.width();
146 double dark_ratio = (double) num_dark_cells / num_total_cells;
147 final int penalty = Math.abs((int) (dark_ratio * 100 - 50)) / 5 * 10;
148 Debug.LOG_INFO("\tApplyMaskPenaltyRule4: " + penalty);
152 // Return the mask bit for "mask_pattern" at "x" and "y".
153 // See 8.8 of JISX0510:2004 for mask pattern conditions.
154 public static int GetDataMaskBit(final int mask_pattern, final int x, final int y) {
155 Debug.DCHECK(QRCode.IsValidMaskPattern(mask_pattern));
156 switch (mask_pattern) {
158 return ((y + x) % 2 == 0) ? 1 : 0;
160 return (y % 2 == 0) ? 1 : 0;
162 return (x % 3 == 0) ? 1 : 0;
164 return ((y + x) % 3 == 0) ? 1 : 0;
166 return (((y / 2) + (x / 3)) % 2 == 0) ? 1 : 0;
168 return (((y * x) % 2) + ((y * x) % 3) == 0) ? 1 : 0;
170 return ((((y * x) % 2) + ((y * x) % 3)) % 2 == 0) ? 1 : 0;
172 return ((((y * x) % 3) + ((y + x) % 2)) % 2 == 0) ? 1 : 0;
176 Debug.LOG_ERROR("invalid mask pattern: " + mask_pattern);
180 // Helper function for ApplyMaskPenaltyRule1. We need this for doing
181 // this calculation in both vertical and horizontal orders
183 private static int ApplyMaskPenaltyRule1Internal(final Matrix matrix, boolean is_horizontal) {
185 int num_same_bit_cells = 0;
188 // for (int i = 0; i < matrix.height(); ++i) {
189 // for (int j = 0; j < matrix.width(); ++j) {
190 // int bit = matrix.get(i, j);
192 // for (int i = 0; i < matrix.width(); ++i) {
193 // for (int j = 0; j < matrix.height(); ++j) {
194 // int bit = matrix.get(j, i);
195 final int i_limit = is_horizontal ? matrix.height() : matrix.width();
196 final int j_limit = is_horizontal ? matrix.width() : matrix.height();
197 for (int i = 0; i < i_limit; ++i) {
198 for (int j = 0; j < j_limit; ++j) {
199 final int bit = is_horizontal ? matrix.get(i, j) : matrix.get(j, i);
200 if (bit == prev_bit) {
201 num_same_bit_cells += 1;
202 // Found five repetitive cells with the same color (bit).
203 // We'll give penalty of 3.
204 if (num_same_bit_cells == 5) {
206 } else if (num_same_bit_cells > 5) {
207 // After five repetitive cells, we'll add the penalty one
212 num_same_bit_cells = 1; // Include the cell itself.
216 num_same_bit_cells = 0; // Clear at each row/column.