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));
43 Debug.LOG_INFO("\tApplyMaskPenaltyRule1: " + penalty);
47 // Apply mask penalty rule 2 and return the penalty. Find 2x2 blocks with the same color and give
50 // JAVAPORT: Consider using ByteMatrix.getArray() instead.
51 public static int ApplyMaskPenaltyRule2(final ByteMatrix 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. Find consecutive cells of 00001011101 or
68 // 10111010000, and give penalty to them. If we find patterns like 000010111010000, we give
69 // penalties twice (i.e. 40 * 2).
71 // JAVAPORT: This many calls to ByteMatrix.get() looks expensive. We should profile and consider
72 // adding a byte[][] ByteMatrix.getArray() method, then using that array locally.
73 public static int ApplyMaskPenaltyRule3(final ByteMatrix matrix) {
75 for (int y = 0; y < matrix.height(); ++y) {
76 for (int x = 0; x < matrix.width(); ++x) {
77 // Tried to simplify following conditions but failed.
78 if (x + 6 < matrix.width() &&
79 matrix.get(y, x + 0) == 1 &&
80 matrix.get(y, x + 1) == 0 &&
81 matrix.get(y, x + 2) == 1 &&
82 matrix.get(y, x + 3) == 1 &&
83 matrix.get(y, x + 4) == 1 &&
84 matrix.get(y, x + 5) == 0 &&
85 matrix.get(y, x + 6) == 1 &&
86 ((x + 10 < matrix.width() &&
87 matrix.get(y, x + 7) == 0 &&
88 matrix.get(y, x + 8) == 0 &&
89 matrix.get(y, x + 9) == 0 &&
90 matrix.get(y, x + 10) == 0) ||
92 matrix.get(y, x - 1) == 0 &&
93 matrix.get(y, x - 2) == 0 &&
94 matrix.get(y, x - 3) == 0 &&
95 matrix.get(y, x - 4) == 0))) {
98 if (y + 6 < matrix.height() &&
99 matrix.get(y + 0, x) == 1 &&
100 matrix.get(y + 1, x) == 0 &&
101 matrix.get(y + 2, x) == 1 &&
102 matrix.get(y + 3, x) == 1 &&
103 matrix.get(y + 4, x) == 1 &&
104 matrix.get(y + 5, x) == 0 &&
105 matrix.get(y + 6, x) == 1 &&
106 ((y + 10 < matrix.height() &&
107 matrix.get(y + 7, x) == 0 &&
108 matrix.get(y + 8, x) == 0 &&
109 matrix.get(y + 9, x) == 0 &&
110 matrix.get(y + 10, x) == 0) ||
112 matrix.get(y - 1, x) == 0 &&
113 matrix.get(y - 2, x) == 0 &&
114 matrix.get(y - 3, x) == 0 &&
115 matrix.get(y - 4, x) == 0))) {
120 Debug.LOG_INFO("\tApplyMaskPenaltyRule3: " + penalty);
124 // Apply mask penalty rule 4 and return the penalty. Calculate the ratio of dark cells and give
125 // penalty if the ratio is far from 50%. It gives 10 penalty for 5% distance. Examples:
133 public static int ApplyMaskPenaltyRule4(final ByteMatrix matrix) {
134 int num_dark_cells = 0;
135 for (int y = 0; y < matrix.height(); ++y) {
136 for (int x = 0; x < matrix.width(); ++x) {
137 if (matrix.get(y, x) == 1) {
142 final int num_total_cells = matrix.height() * matrix.width();
143 double dark_ratio = (double) num_dark_cells / num_total_cells;
144 final int penalty = Math.abs((int) (dark_ratio * 100 - 50)) / 5 * 10;
145 Debug.LOG_INFO("\tApplyMaskPenaltyRule4: " + penalty);
149 // Return the mask bit for "mask_pattern" at "x" and "y". See 8.8 of JISX0510:2004 for mask
150 // pattern conditions.
151 public static int GetDataMaskBit(final int mask_pattern, final int x, final int y) {
152 Debug.DCHECK(QRCode.IsValidMaskPattern(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;
173 Debug.LOG_ERROR("invalid mask pattern: " + mask_pattern);
177 // Helper function for ApplyMaskPenaltyRule1. We need this for doing this calculation in both
178 // vertical and horizontal orders respectively.
179 private static int ApplyMaskPenaltyRule1Internal(final ByteMatrix matrix, boolean is_horizontal) {
181 int num_same_bit_cells = 0;
184 // for (int i = 0; i < matrix.height(); ++i) {
185 // for (int j = 0; j < matrix.width(); ++j) {
186 // int bit = matrix.get(i, j);
188 // for (int i = 0; i < matrix.width(); ++i) {
189 // for (int j = 0; j < matrix.height(); ++j) {
190 // int bit = matrix.get(j, i);
191 final int i_limit = is_horizontal ? matrix.height() : matrix.width();
192 final int j_limit = is_horizontal ? matrix.width() : matrix.height();
193 for (int i = 0; i < i_limit; ++i) {
194 for (int j = 0; j < j_limit; ++j) {
195 final int bit = is_horizontal ? matrix.get(i, j) : matrix.get(j, i);
196 if (bit == prev_bit) {
197 num_same_bit_cells += 1;
198 // Found five repetitive cells with the same color (bit).
199 // We'll give penalty of 3.
200 if (num_same_bit_cells == 5) {
202 } else if (num_same_bit_cells > 5) {
203 // After five repetitive cells, we'll add the penalty one
208 num_same_bit_cells = 1; // Include the cell itself.
212 num_same_bit_cells = 0; // Clear at each row/column.