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;
20 import com.google.zxing.WriterException;
23 * @author satorux@google.com (Satoru Takabayashi) - creator
24 * @author dswitkin@google.com (Daniel Switkin) - ported from C++
26 public final class MatrixUtil {
28 private MatrixUtil() {
32 private static final int[][] POSITION_DETECTION_PATTERN = {
33 {1, 1, 1, 1, 1, 1, 1},
34 {1, 0, 0, 0, 0, 0, 1},
35 {1, 0, 1, 1, 1, 0, 1},
36 {1, 0, 1, 1, 1, 0, 1},
37 {1, 0, 1, 1, 1, 0, 1},
38 {1, 0, 0, 0, 0, 0, 1},
39 {1, 1, 1, 1, 1, 1, 1},
42 private static final int[][] HORIZONTAL_SEPARATION_PATTERN = {
43 {0, 0, 0, 0, 0, 0, 0, 0},
46 private static final int[][] VERTICAL_SEPARATION_PATTERN = {
47 {0}, {0}, {0}, {0}, {0}, {0}, {0},
50 private static final int[][] POSITION_ADJUSTMENT_PATTERN = {
58 // From Appendix E. Table 1, JIS0510X:2004 (p 71). The table was double-checked by komatsu.
59 private static final int[][] POSITION_ADJUSTMENT_PATTERN_COORDINATE_TABLE = {
60 {-1, -1, -1, -1, -1, -1, -1}, // Version 1
61 { 6, 18, -1, -1, -1, -1, -1}, // Version 2
62 { 6, 22, -1, -1, -1, -1, -1}, // Version 3
63 { 6, 26, -1, -1, -1, -1, -1}, // Version 4
64 { 6, 30, -1, -1, -1, -1, -1}, // Version 5
65 { 6, 34, -1, -1, -1, -1, -1}, // Version 6
66 { 6, 22, 38, -1, -1, -1, -1}, // Version 7
67 { 6, 24, 42, -1, -1, -1, -1}, // Version 8
68 { 6, 26, 46, -1, -1, -1, -1}, // Version 9
69 { 6, 28, 50, -1, -1, -1, -1}, // Version 10
70 { 6, 30, 54, -1, -1, -1, -1}, // Version 11
71 { 6, 32, 58, -1, -1, -1, -1}, // Version 12
72 { 6, 34, 62, -1, -1, -1, -1}, // Version 13
73 { 6, 26, 46, 66, -1, -1, -1}, // Version 14
74 { 6, 26, 48, 70, -1, -1, -1}, // Version 15
75 { 6, 26, 50, 74, -1, -1, -1}, // Version 16
76 { 6, 30, 54, 78, -1, -1, -1}, // Version 17
77 { 6, 30, 56, 82, -1, -1, -1}, // Version 18
78 { 6, 30, 58, 86, -1, -1, -1}, // Version 19
79 { 6, 34, 62, 90, -1, -1, -1}, // Version 20
80 { 6, 28, 50, 72, 94, -1, -1}, // Version 21
81 { 6, 26, 50, 74, 98, -1, -1}, // Version 22
82 { 6, 30, 54, 78, 102, -1, -1}, // Version 23
83 { 6, 28, 54, 80, 106, -1, -1}, // Version 24
84 { 6, 32, 58, 84, 110, -1, -1}, // Version 25
85 { 6, 30, 58, 86, 114, -1, -1}, // Version 26
86 { 6, 34, 62, 90, 118, -1, -1}, // Version 27
87 { 6, 26, 50, 74, 98, 122, -1}, // Version 28
88 { 6, 30, 54, 78, 102, 126, -1}, // Version 29
89 { 6, 26, 52, 78, 104, 130, -1}, // Version 30
90 { 6, 30, 56, 82, 108, 134, -1}, // Version 31
91 { 6, 34, 60, 86, 112, 138, -1}, // Version 32
92 { 6, 30, 58, 86, 114, 142, -1}, // Version 33
93 { 6, 34, 62, 90, 118, 146, -1}, // Version 34
94 { 6, 30, 54, 78, 102, 126, 150}, // Version 35
95 { 6, 24, 50, 76, 102, 128, 154}, // Version 36
96 { 6, 28, 54, 80, 106, 132, 158}, // Version 37
97 { 6, 32, 58, 84, 110, 136, 162}, // Version 38
98 { 6, 26, 54, 82, 110, 138, 166}, // Version 39
99 { 6, 30, 58, 86, 114, 142, 170}, // Version 40
102 // Type info cells at the left top corner.
103 private static final int[][] TYPE_INFO_COORDINATES = {
121 // From Appendix D in JISX0510:2004 (p. 67)
122 private static final int VERSION_INFO_POLY = 0x1f25; // 1 1111 0010 0101
124 // From Appendix C in JISX0510:2004 (p.65).
125 private static final int TYPE_INFO_POLY = 0x537;
126 private static final int TYPE_INFO_MASK_PATTERN = 0x5412;
128 // Set all cells to -1. -1 means that the cell is empty (not set yet).
130 // JAVAPORT: We shouldn't need to do this at all. The code should be rewritten to begin encoding
131 // with the ByteMatrix initialized all to zero.
132 public static void clearMatrix(ByteMatrix matrix) {
133 matrix.clear((byte) -1);
136 // Build 2D matrix of QR Code from "dataBits" with "getECLevel", "version" and "getMaskPattern". On
137 // success, store the result in "matrix" and return true. On error, return false.
138 public static void buildMatrix(final BitVector dataBits, int ecLevel, int version,
139 int maskPattern, ByteMatrix matrix) throws WriterException {
140 MatrixUtil.clearMatrix(matrix);
141 embedBasicPatterns(version, matrix);
142 // Type information appear with any version.
143 embedTypeInfo(ecLevel, maskPattern, matrix);
144 // Version info appear if version >= 7.
145 maybeEmbedVersionInfo(version, matrix);
146 // Data should be embedded at end.
147 embedDataBits(dataBits, maskPattern, matrix);
150 // Embed basic patterns. On success, modify the matrix and return true. On error, return false.
151 // The basic patterns are:
152 // - Position detection patterns
154 // - Dark dot at the left bottom corner
155 // - Position adjustment patterns, if need be
156 public static void embedBasicPatterns(int version, ByteMatrix matrix) throws WriterException {
157 // Let's get started with embedding big squares at corners.
158 embedPositionDetectionPatternsAndSeparators(matrix);
159 // Then, embed the dark dot at the left bottom corner.
160 embedDarkDotAtLeftBottomCorner(matrix);
162 // Position adjustment patterns appear if version >= 2.
163 maybeEmbedPositionAdjustmentPatterns(version, matrix);
164 // Timing patterns should be embedded after position adj. patterns.
165 embedTimingPatterns(matrix);
168 // Embed type information. On success, modify the matrix.
169 public static void embedTypeInfo(int ecLevel, int maskPattern, ByteMatrix matrix) throws WriterException {
170 BitVector typeInfoBits = new BitVector();
171 makeTypeInfoBits(ecLevel, maskPattern, typeInfoBits);
173 for (int i = 0; i < typeInfoBits.size(); ++i) {
174 // Place bits in LSB to MSB order. LSB (least significant bit) is the last value in
176 final int bit = typeInfoBits.at(typeInfoBits.size() - 1 - i);
178 // Type info bits at the left top corner. See 8.9 of JISX0510:2004 (p.46).
179 final int x1 = TYPE_INFO_COORDINATES[i][0];
180 final int y1 = TYPE_INFO_COORDINATES[i][1];
181 matrix.set(y1, x1, bit);
185 final int x2 = matrix.width() - i - 1;
187 matrix.set(y2, x2, bit);
189 // Left bottom corner.
191 final int y2 = matrix.height() - 7 + (i - 8);
192 matrix.set(y2, x2, bit);
197 // Embed version information if need be. On success, modify the matrix and return true. On error,
198 // return false. See 8.10 of JISX0510:2004 (p.47) for how to embed version information. Return
199 // true on success, otherwise return false.
200 public static void maybeEmbedVersionInfo(int version, ByteMatrix matrix) throws WriterException {
201 if (version < 7) { // Version info is necessary if version >= 7.
202 return; // Don't need version info.
204 BitVector versionInfoBits = new BitVector();
205 makeVersionInfoBits(version, versionInfoBits);
207 int bitIndex = 6 * 3 - 1; // It will decrease from 17 to 0.
208 for (int i = 0; i < 6; ++i) {
209 for (int j = 0; j < 3; ++j) {
210 // Place bits in LSB (least significant bit) to MSB order.
211 final int bit = versionInfoBits.at(bitIndex);
213 // Left bottom corner.
214 matrix.set(matrix.height() - 11 + j, i, bit);
215 // Right bottom corner.
216 matrix.set(i, matrix.height() - 11 + j, bit);
221 // Embed "dataBits" using "getMaskPattern". On success, modify the matrix and return true. On
222 // error, return false. For debugging purposes, it skips masking process if "getMaskPattern" is -1.
223 // See 8.7 of JISX0510:2004 (p.38) for how to embed data bits.
224 public static void embedDataBits(final BitVector dataBits, int maskPattern, ByteMatrix matrix)
225 throws WriterException {
228 // Start from the right bottom cell.
229 int x = matrix.width() - 1;
230 int y = matrix.height() - 1;
232 // Skip the vertical timing pattern.
236 while (y >= 0 && y < matrix.height()) {
237 for (int i = 0; i < 2; ++i) {
238 final int xx = x - i;
239 // Skip the cell if it's not empty.
240 if (!isEmpty(matrix.get(y, xx))) {
244 if (bitIndex < dataBits.size()) {
245 bit = dataBits.at(bitIndex);
248 // Padding bit. If there is no bit left, we'll fill the left cells with 0, as described
249 // in 8.4.9 of JISX0510:2004 (p. 24).
253 // Skip masking if mask_pattern is -1.
254 if (maskPattern != -1) {
255 final int mask = MaskUtil.getDataMaskBit(maskPattern, xx, y);
258 matrix.set(y, xx, bit);
262 direction = -direction; // Reverse the direction.
264 x -= 2; // Move to the left.
266 // All bits should be consumed.
267 if (bitIndex != dataBits.size()) {
268 throw new WriterException("Not all bits consumed: " + bitIndex + "/" + dataBits.size());
272 // Return the position of the most significant bit set (to one) in the "value". The most
273 // significant bit is position 32. If there is no bit set, return 0. Examples:
274 // - findMSBSet(0) => 0
275 // - findMSBSet(1) => 1
276 // - findMSBSet(255) => 8
277 public static int findMSBSet(int value) {
286 // Calculate BCH (Bose-Chaudhuri-Hocquenghem) code for "value" using polynomial "poly". The BCH
287 // code is used for encoding type information and version information.
288 // Example: Calculation of version information of 7.
289 // f(x) is created from 7.
290 // - 7 = 000111 in 6 bits
291 // - f(x) = x^2 + x^2 + x^1
292 // g(x) is given by the standard (p. 67)
293 // - g(x) = x^12 + x^11 + x^10 + x^9 + x^8 + x^5 + x^2 + 1
294 // Multiply f(x) by x^(18 - 6)
295 // - f'(x) = f(x) * x^(18 - 6)
296 // - f'(x) = x^14 + x^13 + x^12
297 // Calculate the remainder of f'(x) / g(x)
299 // __________________________________________________
300 // g(x) )x^14 + x^13 + x^12
301 // x^14 + x^13 + x^12 + x^11 + x^10 + x^7 + x^4 + x^2
302 // --------------------------------------------------
303 // x^11 + x^10 + x^7 + x^4 + x^2
305 // The remainder is x^11 + x^10 + x^7 + x^4 + x^2
306 // Encode it in binary: 110010010100
307 // The return value is 0xc94 (1100 1001 0100)
309 // Since all coefficients in the polynomials are 1 or 0, we can do the calculation by bit
310 // operations. We don't care if cofficients are positive or negative.
311 public static int calculateBCHCode(int value, int poly) {
312 // If poly is "1 1111 0010 0101" (version info poly), msbSetInPoly is 13. We'll subtract 1
313 // from 13 to make it 12.
314 final int msbSetInPoly = findMSBSet(poly);
315 value <<= msbSetInPoly - 1;
316 // Do the division business using exclusive-or operations.
317 while (findMSBSet(value) >= msbSetInPoly) {
318 value ^= poly << (findMSBSet(value) - msbSetInPoly);
320 // Now the "value" is the remainder (i.e. the BCH code)
324 // Make bit vector of type information. On success, store the result in "bits" and return true.
325 // On error, return false. Encode error correction level and mask pattern. See 8.9 of
326 // JISX0510:2004 (p.45) for details.
327 public static void makeTypeInfoBits(int ecLevel, final int maskPattern, BitVector bits) throws WriterException {
328 final int ecCode = QRCode.getECLevelCode(ecLevel);
329 if (!QRCode.isValidMaskPattern(maskPattern)) {
330 throw new WriterException("Invalid mask pattern");
332 final int typeInfo = (ecCode << 3) | maskPattern;
333 bits.appendBits(typeInfo, 5);
335 final int bchCode = MatrixUtil.calculateBCHCode(typeInfo, TYPE_INFO_POLY);
336 bits.appendBits(bchCode, 10);
338 BitVector maskBits = new BitVector();
339 maskBits.appendBits(TYPE_INFO_MASK_PATTERN, 15);
342 if (bits.size() != 15) { // Just in case.
343 throw new WriterException("should not happen but we got: " + bits.size());
347 // Make bit vector of version information. On success, store the result in "bits" and return true.
348 // On error, return false. See 8.10 of JISX0510:2004 (p.45) for details.
349 public static void makeVersionInfoBits(int version, BitVector bits) throws WriterException {
350 bits.appendBits(version, 6);
351 final int bchCode = MatrixUtil.calculateBCHCode(version, VERSION_INFO_POLY);
352 bits.appendBits(bchCode, 12);
354 if (bits.size() != 18) { // Just in case.
355 throw new WriterException("should not happen but we got: " + bits.size());
359 // Check if "value" is empty.
360 private static boolean isEmpty(final int value) {
364 // Check if "value" is valid.
365 private static boolean isValidValue(final int value) {
366 return (value == -1 || // Empty.
367 value == 0 || // Light (white).
368 value == 1); // Dark (black).
371 private static void embedTimingPatterns(ByteMatrix matrix) throws WriterException {
372 // -8 is for skipping position detection patterns (size 7), and two horizontal/vertical
373 // separation patterns (size 1). Thus, 8 = 7 + 1.
374 for (int i = 8; i < matrix.width() - 8; ++i) {
375 final int bit = (i + 1) % 2;
377 if (!isValidValue(matrix.get(6, i))) {
378 throw new WriterException();
380 if (isEmpty(matrix.get(6, i))) {
381 matrix.set(6, i, bit);
384 if (!isValidValue(matrix.get(i, 6))) {
385 throw new WriterException();
387 if (isEmpty(matrix.get(i, 6))) {
388 matrix.set(i, 6, bit);
393 // Embed the lonely dark dot at left bottom corner. JISX0510:2004 (p.46)
394 private static void embedDarkDotAtLeftBottomCorner(ByteMatrix matrix) throws WriterException {
395 if (matrix.get(matrix.height() - 8, 8) == 0) {
396 throw new WriterException();
398 matrix.set(matrix.height() - 8, 8, 1);
401 private static void embedHorizontalSeparationPattern(final int xStart, final int yStart,
402 ByteMatrix matrix) throws WriterException {
403 // We know the width and height.
404 if (HORIZONTAL_SEPARATION_PATTERN[0].length != 8 || HORIZONTAL_SEPARATION_PATTERN.length != 1) {
405 throw new WriterException("Bad horizontal separation pattern");
407 for (int x = 0; x < 8; ++x) {
408 if (!isEmpty(matrix.get(yStart, xStart + x))) {
409 throw new WriterException();
411 matrix.set(yStart, xStart + x, HORIZONTAL_SEPARATION_PATTERN[0][x]);
415 private static void embedVerticalSeparationPattern(final int xStart, final int yStart,
416 ByteMatrix matrix) throws WriterException {
417 // We know the width and height.
418 if (VERTICAL_SEPARATION_PATTERN[0].length != 1 || VERTICAL_SEPARATION_PATTERN.length != 7) {
419 throw new WriterException("Bad vertical separation pattern");
421 for (int y = 0; y < 7; ++y) {
422 if (!isEmpty(matrix.get(yStart + y, xStart))) {
423 throw new WriterException();
425 matrix.set(yStart + y, xStart, VERTICAL_SEPARATION_PATTERN[y][0]);
429 // Note that we cannot unify the function with embedPositionDetectionPattern() despite they are
430 // almost identical, since we cannot write a function that takes 2D arrays in different sizes in
431 // C/C++. We should live with the fact.
432 private static void embedPositionAdjustmentPattern(final int xStart, final int yStart,
433 ByteMatrix matrix) throws WriterException {
434 // We know the width and height.
435 if (POSITION_ADJUSTMENT_PATTERN[0].length != 5 || POSITION_ADJUSTMENT_PATTERN.length != 5) {
436 throw new WriterException("Bad position adjustment");
438 for (int y = 0; y < 5; ++y) {
439 for (int x = 0; x < 5; ++x) {
440 if (!isEmpty(matrix.get(yStart + y, xStart + x))) {
441 throw new WriterException();
443 matrix.set(yStart + y, xStart + x, POSITION_ADJUSTMENT_PATTERN[y][x]);
448 private static void embedPositionDetectionPattern(final int xStart, final int yStart,
449 ByteMatrix matrix) throws WriterException {
450 // We know the width and height.
451 if (POSITION_DETECTION_PATTERN[0].length != 7 || POSITION_DETECTION_PATTERN.length != 7) {
452 throw new WriterException("Bad position detection pattern");
454 for (int y = 0; y < 7; ++y) {
455 for (int x = 0; x < 7; ++x) {
456 if (!isEmpty(matrix.get(yStart + y, xStart + x))) {
457 throw new WriterException();
459 matrix.set(yStart + y, xStart + x, POSITION_DETECTION_PATTERN[y][x]);
464 // Embed position detection patterns and surrounding vertical/horizontal separators.
465 private static void embedPositionDetectionPatternsAndSeparators(ByteMatrix matrix) throws WriterException {
466 // Embed three big squares at corners.
467 final int pdpWidth = POSITION_DETECTION_PATTERN[0].length;
469 embedPositionDetectionPattern(0, 0, matrix);
471 embedPositionDetectionPattern(matrix.width() - pdpWidth, 0, matrix);
472 // Left bottom corner.
473 embedPositionDetectionPattern(0, matrix.width() - pdpWidth, matrix);
475 // Embed horizontal separation patterns around the squares.
476 final int hspWidth = HORIZONTAL_SEPARATION_PATTERN[0].length;
478 embedHorizontalSeparationPattern(0, hspWidth - 1, matrix);
480 embedHorizontalSeparationPattern(matrix.width() - hspWidth,
481 hspWidth - 1, matrix);
482 // Left bottom corner.
483 embedHorizontalSeparationPattern(0, matrix.width() - hspWidth, matrix);
485 // Embed vertical separation patterns around the squares.
486 final int vspSize = VERTICAL_SEPARATION_PATTERN.length;
488 embedVerticalSeparationPattern(vspSize, 0, matrix);
490 embedVerticalSeparationPattern(matrix.height() - vspSize - 1, 0, matrix);
491 // Left bottom corner.
492 embedVerticalSeparationPattern(vspSize, matrix.height() - vspSize,
496 // Embed position adjustment patterns if need be.
497 private static void maybeEmbedPositionAdjustmentPatterns(final int version, ByteMatrix matrix) throws WriterException {
498 if (version < 2) { // The patterns appear if version >= 2
501 final int index = version - 1;
502 final int[] coordinates = POSITION_ADJUSTMENT_PATTERN_COORDINATE_TABLE[index];
503 final int numCoordinates = POSITION_ADJUSTMENT_PATTERN_COORDINATE_TABLE[index].length;
504 for (int i = 0; i < numCoordinates; ++i) {
505 for (int j = 0; j < numCoordinates; ++j) {
506 final int y = coordinates[i];
507 final int x = coordinates[j];
508 if (x == -1 || y == -1) {
511 // If the cell is unset, we embed the position adjustment pattern here.
512 if (isEmpty(matrix.get(y, x))) {
513 // -2 is necessary since the x/y coordinates point to the center of the pattern, not the
515 embedPositionAdjustmentPattern(x - 2, y - 2, matrix);