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 MatrixUtil {
25 private static final int kPositionDetectionPattern[][] = {
26 {1, 1, 1, 1, 1, 1, 1},
27 {1, 0, 0, 0, 0, 0, 1},
28 {1, 0, 1, 1, 1, 0, 1},
29 {1, 0, 1, 1, 1, 0, 1},
30 {1, 0, 1, 1, 1, 0, 1},
31 {1, 0, 0, 0, 0, 0, 1},
32 {1, 1, 1, 1, 1, 1, 1},
35 private static final int kHorizontalSeparationPattern[][] = {
36 {0, 0, 0, 0, 0, 0, 0, 0},
39 private static final int kVerticalSeparationPattern[][] = {
40 {0}, {0}, {0}, {0}, {0}, {0}, {0},
43 private static final int kPositionAdjustmentPattern[][] = {
51 // From Appendix E. Table 1, JIS0510X:2004 (p 71). The table was double-checked by komatsu.
52 private static final int kPositionAdjustmentPatternCoordinateTable[][] = {
53 {-1, -1, -1, -1, -1, -1, -1}, // Version 1
54 { 6, 18, -1, -1, -1, -1, -1}, // Version 2
55 { 6, 22, -1, -1, -1, -1, -1}, // Version 3
56 { 6, 26, -1, -1, -1, -1, -1}, // Version 4
57 { 6, 30, -1, -1, -1, -1, -1}, // Version 5
58 { 6, 34, -1, -1, -1, -1, -1}, // Version 6
59 { 6, 22, 38, -1, -1, -1, -1}, // Version 7
60 { 6, 24, 42, -1, -1, -1, -1}, // Version 8
61 { 6, 26, 46, -1, -1, -1, -1}, // Version 9
62 { 6, 28, 50, -1, -1, -1, -1}, // Version 10
63 { 6, 30, 54, -1, -1, -1, -1}, // Version 11
64 { 6, 32, 58, -1, -1, -1, -1}, // Version 12
65 { 6, 34, 62, -1, -1, -1, -1}, // Version 13
66 { 6, 26, 46, 66, -1, -1, -1}, // Version 14
67 { 6, 26, 48, 70, -1, -1, -1}, // Version 15
68 { 6, 26, 50, 74, -1, -1, -1}, // Version 16
69 { 6, 30, 54, 78, -1, -1, -1}, // Version 17
70 { 6, 30, 56, 82, -1, -1, -1}, // Version 18
71 { 6, 30, 58, 86, -1, -1, -1}, // Version 19
72 { 6, 34, 62, 90, -1, -1, -1}, // Version 20
73 { 6, 28, 50, 72, 94, -1, -1}, // Version 21
74 { 6, 26, 50, 74, 98, -1, -1}, // Version 22
75 { 6, 30, 54, 78, 102, -1, -1}, // Version 23
76 { 6, 28, 54, 80, 106, -1, -1}, // Version 24
77 { 6, 32, 58, 84, 110, -1, -1}, // Version 25
78 { 6, 30, 58, 86, 114, -1, -1}, // Version 26
79 { 6, 34, 62, 90, 118, -1, -1}, // Version 27
80 { 6, 26, 50, 74, 98, 122, -1}, // Version 28
81 { 6, 30, 54, 78, 102, 126, -1}, // Version 29
82 { 6, 26, 52, 78, 104, 130, -1}, // Version 30
83 { 6, 30, 56, 82, 108, 134, -1}, // Version 31
84 { 6, 34, 60, 86, 112, 138, -1}, // Version 32
85 { 6, 30, 58, 86, 114, 142, -1}, // Version 33
86 { 6, 34, 62, 90, 118, 146, -1}, // Version 34
87 { 6, 30, 54, 78, 102, 126, 150}, // Version 35
88 { 6, 24, 50, 76, 102, 128, 154}, // Version 36
89 { 6, 28, 54, 80, 106, 132, 158}, // Version 37
90 { 6, 32, 58, 84, 110, 136, 162}, // Version 38
91 { 6, 26, 54, 82, 110, 138, 166}, // Version 39
92 { 6, 30, 58, 86, 114, 142, 170}, // Version 40
95 // Type info cells at the left top corner.
96 private static int kTypeInfoCoordinates[][] = {
114 // From Appendix D in JISX0510:2004 (p. 67)
115 private static final int kVersionInfoPoly = 0x1f25; // 1 1111 0010 0101
117 // From Appendix C in JISX0510:2004 (p.65).
118 private static final int kTypeInfoPoly = 0x537;
119 private static final int kTypeInfoMaskPattern = 0x5412;
121 // Set all cells to -1. -1 means that the cell is empty (not set yet).
123 // JAVAPORT: We shouldn't need to do this at all. The code should be rewritten to begin encoding
124 // with the Matrix initialized all to zero.
125 public static void ClearMatrix(Matrix matrix) {
126 matrix.clear((byte) -1);
129 // Build 2D matrix of QR Code from "data_bits" with "ec_level", "version" and "mask_pattern". On
130 // success, store the result in "matrix" and return true. On error, return false.
131 public static boolean BuildMatrix(final BitVector data_bits, int ec_level, int version,
132 int mask_pattern, Matrix matrix) {
133 MatrixUtil.ClearMatrix(matrix);
134 if (!EmbedBasicPatterns(version, matrix)) {
137 // Type information appear with any version.
138 if (!EmbedTypeInfo(ec_level, mask_pattern, matrix)) {
141 // Version info appear if version >= 7.
142 if (!MaybeEmbedVersionInfo(version, matrix)) {
145 // Data should be embedded at end.
146 return EmbedDataBits(data_bits, mask_pattern, matrix);
149 // Embed basic patterns. On success, modify the matrix and return true. On error, return false.
150 // The basic patterns are:
151 // - Position detection patterns
153 // - Dark dot at the left bottom corner
154 // - Position adjustment patterns, if need be
155 public static boolean EmbedBasicPatterns(int version, Matrix matrix) {
156 // Let's get started with embedding big squares at corners.
157 EmbedPositionDetectionPatternsAndSeparators(matrix);
158 // Then, embed the dark dot at the left bottom corner.
159 EmbedDarkDotAtLeftBottomCorner(matrix);
161 // Position adjustment patterns appear if version >= 2.
162 MaybeEmbedPositionAdjustmentPatterns(version, matrix);
163 // Timing patterns should be embedded after position adj. patterns.
164 EmbedTimingPatterns(matrix);
168 // Embed type information. On success, modify the matrix and return true. On error, return false.
169 public static boolean EmbedTypeInfo(int ec_level, int mask_pattern, Matrix matrix) {
170 BitVector type_info_bits = new BitVector();
171 if (!MakeTypeInfoBits(ec_level, mask_pattern, type_info_bits)) {
174 Debug.DCHECK_EQ(15, type_info_bits.size());
176 for (int i = 0; i < type_info_bits.size(); ++i) {
177 // Place bits in LSB to MSB order. LSB (least significant bit) is the last value in
179 final int bit = type_info_bits.at(type_info_bits.size() - 1 - i);
181 // Type info bits at the left top corner. See 8.9 of JISX0510:2004 (p.46).
182 final int x1 = kTypeInfoCoordinates[i][0];
183 final int y1 = kTypeInfoCoordinates[i][1];
184 matrix.set(y1, x1, bit);
188 final int x2 = matrix.width() - i - 1;
190 matrix.set(y2, x2, bit);
192 // Left bottom corner.
194 final int y2 = matrix.height() - 7 + (i - 8);
195 matrix.set(y2, x2, bit);
201 // Embed version information if need be. On success, modify the matrix and return true. On error,
202 // return false. See 8.10 of JISX0510:2004 (p.47) for how to embed version information. Return
203 // true on success, otherwise return false.
204 public static boolean MaybeEmbedVersionInfo(int version, Matrix matrix) {
205 if (version < 7) { // Version info is necessary if version >= 7.
206 return true; // Don't need version info.
208 BitVector version_info_bits = new BitVector();
209 if (!MakeVersionInfoBits(version, version_info_bits)) {
213 Debug.DCHECK_EQ(18, version_info_bits.size());
214 int bit_index = 6 * 3 - 1; // It will decrease from 17 to 0.
215 for (int i = 0; i < 6; ++i) {
216 for (int j = 0; j < 3; ++j) {
217 // Place bits in LSB (least significant bit) to MSB order.
218 final int bit = version_info_bits.at(bit_index);
220 // Left bottom corner.
221 matrix.set(matrix.height() - 11 + j, i, bit);
222 // Right bottom corner.
223 matrix.set(i, matrix.height() - 11 + j, bit);
229 // Embed "data_bits" using "mask_pattern". On success, modify the matrix and return true. On
230 // error, return false. For debugging purposes, it skips masking process if "mask_pattern" is -1.
231 // See 8.7 of JISX0510:2004 (p.38) for how to embed data bits.
232 public static boolean EmbedDataBits(final BitVector data_bits, int mask_pattern, Matrix matrix) {
235 // Start from the right bottom cell.
236 int x = matrix.width() - 1;
237 int y = matrix.height() - 1;
239 // Skip the vertical timing pattern.
243 while (y >= 0 && y < matrix.height()) {
244 for (int i = 0; i < 2; ++i) {
245 final int xx = x - i;
246 // Skip the cell if it's not empty.
247 if (!IsEmpty(matrix.get(y, xx))) {
251 if (bit_index < data_bits.size()) {
252 bit = data_bits.at(bit_index);
255 // Padding bit. If there is no bit left, we'll fill the left cells with 0, as described
256 // in 8.4.9 of JISX0510:2004 (p. 24).
259 Debug.DCHECK(IsValidValue(bit));
261 // Skip masking if mask_pattern is -1.
262 if (mask_pattern != -1) {
263 final int mask = MaskUtil.GetDataMaskBit(mask_pattern, xx, y);
264 Debug.DCHECK(mask == 0 || mask == 1);
267 matrix.set(y, xx, bit);
271 direction = -direction; // Reverse the direction.
273 x -= 2; // Move to the left.
275 // All bits should be consumed.
276 if (bit_index < data_bits.size()) {
277 Debug.LOG_ERROR("Not all bits consumed: " + bit_index + "/" + data_bits.size());
280 Debug.DCHECK_EQ(bit_index, data_bits.size());
284 // Return the position of the most significant bit set (to one) in the "value". The most
285 // significant bit is position 32. If there is no bit set, return 0. Examples:
286 // - FindMSBSet(0) => 0
287 // - FindMSBSet(1) => 1
288 // - FindMSBSet(255) => 8
289 public static int FindMSBSet(int value) {
298 // Calculate BCH (Bose-Chaudhuri-Hocquenghem) code for "value" using polynomial "poly". The BCH
299 // code is used for encoding type information and version information.
300 // Example: Calculation of version information of 7.
301 // f(x) is created from 7.
302 // - 7 = 000111 in 6 bits
303 // - f(x) = x^2 + x^2 + x^1
304 // g(x) is given by the standard (p. 67)
305 // - g(x) = x^12 + x^11 + x^10 + x^9 + x^8 + x^5 + x^2 + 1
306 // Multiply f(x) by x^(18 - 6)
307 // - f'(x) = f(x) * x^(18 - 6)
308 // - f'(x) = x^14 + x^13 + x^12
309 // Calculate the remainder of f'(x) / g(x)
311 // __________________________________________________
312 // g(x) )x^14 + x^13 + x^12
313 // x^14 + x^13 + x^12 + x^11 + x^10 + x^7 + x^4 + x^2
314 // --------------------------------------------------
315 // x^11 + x^10 + x^7 + x^4 + x^2
317 // The remainder is x^11 + x^10 + x^7 + x^4 + x^2
318 // Encode it in binary: 110010010100
319 // The return value is 0xc94 (1100 1001 0100)
321 // Since all coefficients in the polynomials are 1 or 0, we can do the calculation by bit
322 // operations. We don't care if cofficients are positive or negative.
323 public static int CalculateBCHCode(int value, int poly) {
324 // If poly is "1 1111 0010 0101" (version info poly), msb_set_in_poly is 13. We'll subtract 1
325 // from 13 to make it 12.
326 final int msb_set_in_poly = FindMSBSet(poly);
327 value <<= msb_set_in_poly - 1;
328 // Do the division business using exclusive-or operations.
329 while (FindMSBSet(value) >= msb_set_in_poly) {
330 value ^= poly << (FindMSBSet(value) - msb_set_in_poly);
332 // Now the "value" is the remainder (i.e. the BCH code)
336 // Make bit vector of type information. On success, store the result in "bits" and return true.
337 // On error, return false. Encode error correction level and mask pattern. See 8.9 of
338 // JISX0510:2004 (p.45) for details.
339 public static boolean MakeTypeInfoBits(int ec_level, final int mask_pattern, BitVector bits) {
340 final int ec_code = QRCode.GetECLevelCode(ec_level);
344 if (!QRCode.IsValidMaskPattern(mask_pattern)) {
347 final int type_info = (ec_code << 3) | mask_pattern;
348 bits.AppendBits(type_info, 5);
350 final int bch_code = MatrixUtil.CalculateBCHCode(type_info, kTypeInfoPoly);
351 bits.AppendBits(bch_code, 10);
353 BitVector mask_bits = new BitVector();
354 mask_bits.AppendBits(kTypeInfoMaskPattern, 15);
357 if (bits.size() != 15) { // Just in case.
358 Debug.LOG_ERROR("should not happen but we got: " + bits.size());
364 // Make bit vector of version information. On success, store the result in "bits" and return true.
365 // On error, return false. See 8.10 of JISX0510:2004 (p.45) for details.
366 public static boolean MakeVersionInfoBits(int version, BitVector bits) {
367 bits.AppendBits(version, 6);
368 final int bch_code = MatrixUtil.CalculateBCHCode(version, kVersionInfoPoly);
369 bits.AppendBits(bch_code, 12);
371 if (bits.size() != 18) { // Just in case.
372 Debug.LOG_ERROR("should not happen but we got: " + bits.size());
378 // Check if "value" is empty.
379 private static boolean IsEmpty(final int value) {
383 // Check if "value" is valid.
384 private static boolean IsValidValue(final int value) {
385 return (value == -1 || // Empty.
386 value == 0 || // Light (white).
387 value == 1); // Dark (black).
390 private static void EmbedTimingPatterns(Matrix matrix) {
391 // -8 is for skipping position detection patterns (size 7), and two horizontal/vertical
392 // separation patterns (size 1). Thus, 8 = 7 + 1.
393 for (int i = 8; i < matrix.width() - 8; ++i) {
394 final int bit = (i + 1) % 2;
396 Debug.DCHECK(IsValidValue(matrix.get(6, i)));
397 if (IsEmpty(matrix.get(6, i))) {
398 matrix.set(6, i, bit);
401 Debug.DCHECK(IsValidValue(matrix.get(i, 6)));
402 if (IsEmpty(matrix.get(i, 6))) {
403 matrix.set(i, 6, bit);
408 // Embed the lonely dark dot at left bottom corner. JISX0510:2004 (p.46)
409 private static void EmbedDarkDotAtLeftBottomCorner(Matrix matrix) {
410 Debug.DCHECK(matrix.get(matrix.height() - 8, 8) != 0);
411 matrix.set(matrix.height() - 8, 8, 1);
414 private static void EmbedHorizontalSeparationPattern(final int x_start, final int y_start,
416 // We know the width and height.
417 Debug.DCHECK_EQ(8, kHorizontalSeparationPattern[0].length);
418 Debug.DCHECK_EQ(1, kHorizontalSeparationPattern.length);
419 for (int x = 0; x < 8; ++x) {
420 Debug.DCHECK(IsEmpty(matrix.get(y_start, x_start + x)));
421 matrix.set(y_start, x_start + x, kHorizontalSeparationPattern[0][x]);
425 private static void EmbedVerticalSeparationPattern(final int x_start, final int y_start,
427 // We know the width and height.
428 Debug.DCHECK_EQ(1, kVerticalSeparationPattern[0].length);
429 Debug.DCHECK_EQ(7, kVerticalSeparationPattern.length);
430 for (int y = 0; y < 7; ++y) {
431 Debug.DCHECK(IsEmpty(matrix.get(y_start + y, x_start)));
432 matrix.set(y_start + y, x_start, kVerticalSeparationPattern[y][0]);
436 // Note that we cannot unify the function with EmbedPositionDetectionPattern() despite they are
437 // almost identical, since we cannot write a function that takes 2D arrays in different sizes in
438 // C/C++. We should live with the fact.
439 private static void EmbedPositionAdjustmentPattern(final int x_start, final int y_start,
441 // We know the width and height.
442 Debug.DCHECK_EQ(5, kPositionAdjustmentPattern[0].length);
443 Debug.DCHECK_EQ(5, kPositionAdjustmentPattern.length);
444 for (int y = 0; y < 5; ++y) {
445 for (int x = 0; x < 5; ++x) {
446 Debug.DCHECK(IsEmpty(matrix.get(y_start + y, x_start + x)));
447 matrix.set(y_start + y, x_start + x, kPositionAdjustmentPattern[y][x]);
452 private static void EmbedPositionDetectionPattern(final int x_start, final int y_start,
454 // We know the width and height.
455 Debug.DCHECK_EQ(7, kPositionDetectionPattern[0].length);
456 Debug.DCHECK_EQ(7, kPositionDetectionPattern.length);
457 for (int y = 0; y < 7; ++y) {
458 for (int x = 0; x < 7; ++x) {
459 Debug.DCHECK(IsEmpty(matrix.get(y_start + y, x_start + x)));
460 matrix.set(y_start + y, x_start + x, kPositionDetectionPattern[y][x]);
465 // Embed position detection patterns and surrounding vertical/horizontal separators.
466 private static void EmbedPositionDetectionPatternsAndSeparators(Matrix matrix) {
467 // Embed three big squares at corners.
468 final int pdp_width = kPositionDetectionPattern[0].length;
470 EmbedPositionDetectionPattern(0, 0, matrix);
472 EmbedPositionDetectionPattern(matrix.width() - pdp_width, 0, matrix);
473 // Left bottom corner.
474 EmbedPositionDetectionPattern(0, matrix.width() - pdp_width, matrix);
476 // Embed horizontal separation patterns around the squares.
477 final int hsp_width = kHorizontalSeparationPattern[0].length;
479 EmbedHorizontalSeparationPattern(0, hsp_width - 1, matrix);
481 EmbedHorizontalSeparationPattern(matrix.width() - hsp_width,
482 hsp_width - 1, matrix);
483 // Left bottom corner.
484 EmbedHorizontalSeparationPattern(0, matrix.width() - hsp_width, matrix);
486 // Embed vertical separation patterns around the squares.
487 final int vsp_size = kVerticalSeparationPattern.length;
489 EmbedVerticalSeparationPattern(vsp_size, 0, matrix);
491 EmbedVerticalSeparationPattern(matrix.height() - vsp_size - 1, 0, matrix);
492 // Left bottom corner.
493 EmbedVerticalSeparationPattern(vsp_size, matrix.height() - vsp_size,
497 // Embed position adjustment patterns if need be.
498 private static void MaybeEmbedPositionAdjustmentPatterns(final int version, Matrix matrix) {
499 if (version < 2) { // The patterns appear if version >= 2
502 final int index = version - 1;
503 final int[] coordinates = kPositionAdjustmentPatternCoordinateTable[index];
504 final int num_coordinates = kPositionAdjustmentPatternCoordinateTable[index].length;
505 for (int i = 0; i < num_coordinates; ++i) {
506 for (int j = 0; j < num_coordinates; ++j) {
507 final int y = coordinates[i];
508 final int x = coordinates[j];
509 if (x == -1 || y == -1) {
512 // If the cell is unset, we embed the position adjustment pattern here.
513 if (IsEmpty(matrix.get(y, x))) {
514 // -2 is necessary since the x/y coordinates point to the center of the pattern, not the
516 EmbedPositionAdjustmentPattern(x - 2, y - 2, matrix);