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 {
29 // Apply mask penalty rule 1 and return the penalty. Find repetitive cells with the same color and
30 // give penalty to them. Example: 00000 or 11111.
31 public static int applyMaskPenaltyRule1(ByteMatrix matrix) {
32 return applyMaskPenaltyRule1Internal(matrix, true) + applyMaskPenaltyRule1Internal(matrix, false);
35 // Apply mask penalty rule 2 and return the penalty. Find 2x2 blocks with the same color and give
37 public static int applyMaskPenaltyRule2(ByteMatrix matrix) {
39 byte[][] array = matrix.getArray();
40 int width = matrix.getWidth();
41 int height = matrix.getHeight();
42 for (int y = 0; y < height - 1; ++y) {
43 for (int x = 0; x < width - 1; ++x) {
44 int value = array[y][x];
45 if (value == array[y][x + 1] && value == array[y + 1][x] && value == array[y + 1][x + 1]) {
53 // Apply mask penalty rule 3 and return the penalty. Find consecutive cells of 00001011101 or
54 // 10111010000, and give penalty to them. If we find patterns like 000010111010000, we give
55 // penalties twice (i.e. 40 * 2).
56 public static int applyMaskPenaltyRule3(ByteMatrix matrix) {
58 byte[][] array = matrix.getArray();
59 int width = matrix.getWidth();
60 int height = matrix.getHeight();
61 for (int y = 0; y < height; ++y) {
62 for (int x = 0; x < width; ++x) {
63 // Tried to simplify following conditions but failed.
66 array[y][x + 1] == 0 &&
67 array[y][x + 2] == 1 &&
68 array[y][x + 3] == 1 &&
69 array[y][x + 4] == 1 &&
70 array[y][x + 5] == 0 &&
71 array[y][x + 6] == 1 &&
73 array[y][x + 7] == 0 &&
74 array[y][x + 8] == 0 &&
75 array[y][x + 9] == 0 &&
76 array[y][x + 10] == 0) ||
78 array[y][x - 1] == 0 &&
79 array[y][x - 2] == 0 &&
80 array[y][x - 3] == 0 &&
81 array[y][x - 4] == 0))) {
86 array[y + 1][x] == 0 &&
87 array[y + 2][x] == 1 &&
88 array[y + 3][x] == 1 &&
89 array[y + 4][x] == 1 &&
90 array[y + 5][x] == 0 &&
91 array[y + 6][x] == 1 &&
93 array[y + 7][x] == 0 &&
94 array[y + 8][x] == 0 &&
95 array[y + 9][x] == 0 &&
96 array[y + 10][x] == 0) ||
98 array[y - 1][x] == 0 &&
99 array[y - 2][x] == 0 &&
100 array[y - 3][x] == 0 &&
101 array[y - 4][x] == 0))) {
109 // Apply mask penalty rule 4 and return the penalty. Calculate the ratio of dark cells and give
110 // penalty if the ratio is far from 50%. It gives 10 penalty for 5% distance. Examples:
118 public static int applyMaskPenaltyRule4(ByteMatrix matrix) {
119 int numDarkCells = 0;
120 byte[][] array = matrix.getArray();
121 int width = matrix.getWidth();
122 int height = matrix.getHeight();
123 for (int y = 0; y < height; ++y) {
124 for (int x = 0; x < width; ++x) {
125 if (array[y][x] == 1) {
130 int numTotalCells = matrix.getHeight() * matrix.getWidth();
131 double darkRatio = (double) numDarkCells / numTotalCells;
132 return Math.abs((int) (darkRatio * 100 - 50)) / 5 * 10;
135 // Return the mask bit for "getMaskPattern" at "x" and "y". See 8.8 of JISX0510:2004 for mask
136 // pattern conditions.
137 public static boolean getDataMaskBit(int maskPattern, int x, int y) {
138 if (!QRCode.isValidMaskPattern(maskPattern)) {
139 throw new IllegalArgumentException("Invalid mask pattern");
141 int intermediate, temp;
142 switch (maskPattern) {
144 intermediate = (y + x) & 0x1;
147 intermediate = y & 0x1;
150 intermediate = x % 3;
153 intermediate = (y + x) % 3;
156 intermediate = ((y >>> 1) + (x / 3)) & 0x1;
160 intermediate = (temp & 0x1) + (temp % 3);
164 intermediate = (((temp & 0x1) + (temp % 3)) & 0x1);
168 intermediate = (((temp % 3) + ((y + x) & 0x1)) & 0x1);
171 throw new IllegalArgumentException("Invalid mask pattern: " + maskPattern);
173 return intermediate == 0;
176 // Helper function for applyMaskPenaltyRule1. We need this for doing this calculation in both
177 // vertical and horizontal orders respectively.
178 private static int applyMaskPenaltyRule1Internal(ByteMatrix matrix, boolean isHorizontal) {
180 int numSameBitCells = 0;
183 // for (int i = 0; i < matrix.height(); ++i) {
184 // for (int j = 0; j < matrix.width(); ++j) {
185 // int bit = matrix.get(i, j);
187 // for (int i = 0; i < matrix.width(); ++i) {
188 // for (int j = 0; j < matrix.height(); ++j) {
189 // int bit = matrix.get(j, i);
190 int iLimit = isHorizontal ? matrix.getHeight() : matrix.getWidth();
191 int jLimit = isHorizontal ? matrix.getWidth() : matrix.getHeight();
192 byte[][] array = matrix.getArray();
193 for (int i = 0; i < iLimit; ++i) {
194 for (int j = 0; j < jLimit; ++j) {
195 int bit = isHorizontal ? array[i][j] : array[j][i];
196 if (bit == prevBit) {
197 numSameBitCells += 1;
198 // Found five repetitive cells with the same color (bit).
199 // We'll give penalty of 3.
200 if (numSameBitCells == 5) {
202 } else if (numSameBitCells > 5) {
203 // After five repetitive cells, we'll add the penalty one
208 numSameBitCells = 1; // Include the cell itself.
212 numSameBitCells = 0; // Clear at each row/column.