2 * QR Code generator library (C++)
4 * Copyright (c) Project Nayuki. (MIT License)
5 * https://www.nayuki.io/page/qr-code-generator-library
7 * Permission is hereby granted, free of charge, to any person obtaining a copy of
8 * this software and associated documentation files (the "Software"), to deal in
9 * the Software without restriction, including without limitation the rights to
10 * use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of
11 * the Software, and to permit persons to whom the Software is furnished to do so,
12 * subject to the following conditions:
13 * - The above copyright notice and this permission notice shall be included in
14 * all copies or substantial portions of the Software.
15 * - The Software is provided "as is", without warranty of any kind, express or
16 * implied, including but not limited to the warranties of merchantability,
17 * fitness for a particular purpose and noninfringement. In no event shall the
18 * authors or copyright holders be liable for any claim, damages or other
19 * liability, whether in an action of contract, tort or otherwise, arising from,
20 * out of or in connection with the Software or the use or other dealings in the
36 * A segment of character/binary/control data in a QR Code symbol.
37 * Instances of this class are immutable.
38 * The mid-level way to create a segment is to take the payload data
39 * and call a static factory function such as QrSegment::makeNumeric().
40 * The low-level way to create a segment is to custom-make the bit buffer
41 * and call the QrSegment() constructor with appropriate values.
42 * This segment class imposes no length restrictions, but QR Codes have restrictions.
43 * Even in the most favorable conditions, a QR Code can only hold 7089 characters of data.
44 * Any segment longer than this is meaningless for the purpose of generating QR Codes.
46 class QrSegment final {
48 /*---- Public helper enumeration ----*/
51 * Describes how a segment's data bits are interpreted. Immutable.
53 public: class Mode final {
57 public: static const Mode NUMERIC;
58 public: static const Mode ALPHANUMERIC;
59 public: static const Mode BYTE;
60 public: static const Mode KANJI;
61 public: static const Mode ECI;
66 // The mode indicator bits, which is a uint4 value (range 0 to 15).
67 private: int modeBits;
69 // Number of character count bits for three different version ranges.
70 private: int numBitsCharCount[3];
75 private: Mode(int mode, int cc0, int cc1, int cc2);
81 * (Package-private) Returns the mode indicator bits, which is an unsigned 4-bit value (range 0 to 15).
83 public: int getModeBits() const;
86 * (Package-private) Returns the bit width of the character count field for a segment in
87 * this mode in a QR Code at the given version number. The result is in the range [0, 16].
89 public: int numCharCountBits(int ver) const;
95 /*---- Static factory functions (mid level) ----*/
98 * Returns a segment representing the given binary data encoded in
99 * byte mode. All input byte vectors are acceptable. Any text string
100 * can be converted to UTF-8 bytes and encoded as a byte mode segment.
102 public: static QrSegment makeBytes(const std::vector<std::uint8_t> &data);
106 * Returns a segment representing the given string of decimal digits encoded in numeric mode.
108 public: static QrSegment makeNumeric(const char *digits);
112 * Returns a segment representing the given text string encoded in alphanumeric mode.
113 * The characters allowed are: 0 to 9, A to Z (uppercase only), space,
114 * dollar, percent, asterisk, plus, hyphen, period, slash, colon.
116 public: static QrSegment makeAlphanumeric(const char *text);
120 * Returns a list of zero or more segments to represent the given text string. The result
121 * may use various segment modes and switch modes to optimize the length of the bit stream.
123 public: static std::vector<QrSegment> makeSegments(const char *text);
127 * Returns a segment representing an Extended Channel Interpretation
128 * (ECI) designator with the given assignment value.
130 public: static QrSegment makeEci(long assignVal);
133 /*---- Public static helper functions ----*/
136 * Tests whether the given string can be encoded as a segment in alphanumeric mode.
137 * A string is encodable iff each character is in the following set: 0 to 9, A to Z
138 * (uppercase only), space, dollar, percent, asterisk, plus, hyphen, period, slash, colon.
140 public: static bool isAlphanumeric(const char *text);
144 * Tests whether the given string can be encoded as a segment in numeric mode.
145 * A string is encodable iff each character is in the range 0 to 9.
147 public: static bool isNumeric(const char *text);
151 /*---- Instance fields ----*/
153 /* The mode indicator of this segment. Accessed through getMode(). */
156 /* The length of this segment's unencoded data. Measured in characters for
157 * numeric/alphanumeric/kanji mode, bytes for byte mode, and 0 for ECI mode.
158 * Always zero or positive. Not the same as the data's bit length.
159 * Accessed through getNumChars(). */
160 private: int numChars;
162 /* The data bits of this segment. Accessed through getData(). */
163 private: std::vector<bool> data;
166 /*---- Constructors (low level) ----*/
169 * Creates a new QR Code segment with the given attributes and data.
170 * The character count (numCh) must agree with the mode and the bit buffer length,
171 * but the constraint isn't checked. The given bit buffer is copied and stored.
173 public: QrSegment(Mode md, int numCh, const std::vector<bool> &dt);
177 * Creates a new QR Code segment with the given parameters and data.
178 * The character count (numCh) must agree with the mode and the bit buffer length,
179 * but the constraint isn't checked. The given bit buffer is moved and stored.
181 public: QrSegment(Mode md, int numCh, std::vector<bool> &&dt);
184 /*---- Methods ----*/
187 * Returns the mode field of this segment.
189 public: Mode getMode() const;
193 * Returns the character count field of this segment.
195 public: int getNumChars() const;
199 * Returns the data bits of this segment.
201 public: const std::vector<bool> &getData() const;
204 // (Package-private) Calculates the number of bits needed to encode the given segments at
205 // the given version. Returns a non-negative number if successful. Otherwise returns -1 if a
206 // segment has too many characters to fit its length field, or the total bits exceeds INT_MAX.
207 public: static int getTotalBits(const std::vector<QrSegment> &segs, int version);
210 /*---- Private constant ----*/
212 /* The set of all legal characters in alphanumeric mode, where
213 * each character value maps to the index in the string. */
214 private: static const char *ALPHANUMERIC_CHARSET;
221 * A QR Code symbol, which is a type of two-dimension barcode.
222 * Invented by Denso Wave and described in the ISO/IEC 18004 standard.
223 * Instances of this class represent an immutable square grid of black and white cells.
224 * The class provides static factory functions to create a QR Code from text or binary data.
225 * The class covers the QR Code Model 2 specification, supporting all versions (sizes)
226 * from 1 to 40, all 4 error correction levels, and 4 character encoding modes.
228 * Ways to create a QR Code object:
229 * - High level: Take the payload data and call QrCode::encodeText() or QrCode::encodeBinary().
230 * - Mid level: Custom-make the list of segments and call QrCode::encodeSegments().
231 * - Low level: Custom-make the array of data codeword bytes (including
232 * segment headers and final padding, excluding error correction codewords),
233 * supply the appropriate version number, and call the QrCode() constructor.
234 * (Note that all ways require supplying the desired error correction level.)
238 /*---- Public helper enumeration ----*/
241 * The error correction level in a QR Code symbol.
243 public: enum class Ecc {
244 LOW = 0 , // The QR Code can tolerate about 7% erroneous codewords
245 MEDIUM , // The QR Code can tolerate about 15% erroneous codewords
246 QUARTILE, // The QR Code can tolerate about 25% erroneous codewords
247 HIGH , // The QR Code can tolerate about 30% erroneous codewords
251 // Returns a value in the range 0 to 3 (unsigned 2-bit integer).
252 private: static int getFormatBits(Ecc ecl);
256 /*---- Static factory functions (high level) ----*/
259 * Returns a QR Code representing the given Unicode text string at the given error correction level.
260 * As a conservative upper bound, this function is guaranteed to succeed for strings that have 2953 or fewer
261 * UTF-8 code units (not Unicode code points) if the low error correction level is used. The smallest possible
262 * QR Code version is automatically chosen for the output. The ECC level of the result may be higher than
263 * the ecl argument if it can be done without increasing the version.
265 public: static QrCode encodeText(const char *text, Ecc ecl);
269 * Returns a QR Code representing the given binary data at the given error correction level.
270 * This function always encodes using the binary segment mode, not any text mode. The maximum number of
271 * bytes allowed is 2953. The smallest possible QR Code version is automatically chosen for the output.
272 * The ECC level of the result may be higher than the ecl argument if it can be done without increasing the version.
274 public: static QrCode encodeBinary(const std::vector<std::uint8_t> &data, Ecc ecl);
277 /*---- Static factory functions (mid level) ----*/
280 * Returns a QR Code representing the given segments with the given encoding parameters.
281 * The smallest possible QR Code version within the given range is automatically
282 * chosen for the output. Iff boostEcl is true, then the ECC level of the result
283 * may be higher than the ecl argument if it can be done without increasing the
284 * version. The mask number is either between 0 to 7 (inclusive) to force that
285 * mask, or -1 to automatically choose an appropriate mask (which may be slow).
286 * This function allows the user to create a custom sequence of segments that switches
287 * between modes (such as alphanumeric and byte) to encode text in less space.
288 * This is a mid-level API; the high-level API is encodeText() and encodeBinary().
290 public: static QrCode encodeSegments(const std::vector<QrSegment> &segs, Ecc ecl,
291 int minVersion=1, int maxVersion=40, int mask=-1, bool boostEcl=true); // All optional parameters
295 /*---- Instance fields ----*/
297 // Immutable scalar parameters:
299 /* The version number of this QR Code, which is between 1 and 40 (inclusive).
300 * This determines the size of this barcode. */
301 private: int version;
303 /* The width and height of this QR Code, measured in modules, between
304 * 21 and 177 (inclusive). This is equal to version * 4 + 17. */
307 /* The error correction level used in this QR Code. */
308 private: Ecc errorCorrectionLevel;
310 /* The index of the mask pattern used in this QR Code, which is between 0 and 7 (inclusive).
311 * Even if a QR Code is created with automatic masking requested (mask = -1),
312 * the resulting object still has a mask value between 0 and 7. */
315 // Private grids of modules/pixels, with dimensions of size*size:
317 // The modules of this QR Code (false = white, true = black).
318 // Immutable after constructor finishes. Accessed through getModule().
319 private: std::vector<std::vector<bool> > modules;
321 // Indicates function modules that are not subjected to masking. Discarded when constructor finishes.
322 private: std::vector<std::vector<bool> > isFunction;
326 /*---- Constructor (low level) ----*/
329 * Creates a new QR Code with the given version number,
330 * error correction level, data codeword bytes, and mask number.
331 * This is a low-level API that most users should not use directly.
332 * A mid-level API is the encodeSegments() function.
334 public: QrCode(int ver, Ecc ecl, const std::vector<std::uint8_t> &dataCodewords, int msk);
338 /*---- Public instance methods ----*/
341 * Returns this QR Code's version, in the range [1, 40].
343 public: int getVersion() const;
347 * Returns this QR Code's size, in the range [21, 177].
349 public: int getSize() const;
353 * Returns this QR Code's error correction level.
355 public: Ecc getErrorCorrectionLevel() const;
359 * Returns this QR Code's mask, in the range [0, 7].
361 public: int getMask() const;
365 * Returns the color of the module (pixel) at the given coordinates, which is false
366 * for white or true for black. The top left corner has the coordinates (x=0, y=0).
367 * If the given coordinates are out of bounds, then false (white) is returned.
369 public: bool getModule(int x, int y) const;
373 * Returns a string of SVG code for an image depicting this QR Code, with the given number
374 * of border modules. The string always uses Unix newlines (\n), regardless of the platform.
376 public: std::string toSvgString(int border) const;
380 /*---- Private helper methods for constructor: Drawing function modules ----*/
382 // Reads this object's version field, and draws and marks all function modules.
383 private: void drawFunctionPatterns();
386 // Draws two copies of the format bits (with its own error correction code)
387 // based on the given mask and this object's error correction level field.
388 private: void drawFormatBits(int msk);
391 // Draws two copies of the version bits (with its own error correction code),
392 // based on this object's version field, iff 7 <= version <= 40.
393 private: void drawVersion();
396 // Draws a 9*9 finder pattern including the border separator,
397 // with the center module at (x, y). Modules can be out of bounds.
398 private: void drawFinderPattern(int x, int y);
401 // Draws a 5*5 alignment pattern, with the center module
402 // at (x, y). All modules must be in bounds.
403 private: void drawAlignmentPattern(int x, int y);
406 // Sets the color of a module and marks it as a function module.
407 // Only used by the constructor. Coordinates must be in bounds.
408 private: void setFunctionModule(int x, int y, bool isBlack);
411 // Returns the color of the module at the given coordinates, which must be in range.
412 private: bool module(int x, int y) const;
415 /*---- Private helper methods for constructor: Codewords and masking ----*/
417 // Returns a new byte string representing the given data with the appropriate error correction
418 // codewords appended to it, based on this object's version and error correction level.
419 private: std::vector<std::uint8_t> addEccAndInterleave(const std::vector<std::uint8_t> &data) const;
422 // Draws the given sequence of 8-bit codewords (data and error correction) onto the entire
423 // data area of this QR Code. Function modules need to be marked off before this is called.
424 private: void drawCodewords(const std::vector<std::uint8_t> &data);
427 // XORs the codeword modules in this QR Code with the given mask pattern.
428 // The function modules must be marked and the codeword bits must be drawn
429 // before masking. Due to the arithmetic of XOR, calling applyMask() with
430 // the same mask value a second time will undo the mask. A final well-formed
431 // QR Code needs exactly one (not zero, two, etc.) mask applied.
432 private: void applyMask(int msk);
435 // Calculates and returns the penalty score based on state of this QR Code's current modules.
436 // This is used by the automatic mask choice algorithm to find the mask pattern that yields the lowest score.
437 private: long getPenaltyScore() const;
441 /*---- Private helper functions ----*/
443 // Returns an ascending list of positions of alignment patterns for this version number.
444 // Each position is in the range [0,177), and are used on both the x and y axes.
445 // This could be implemented as lookup table of 40 variable-length lists of unsigned bytes.
446 private: std::vector<int> getAlignmentPatternPositions() const;
449 // Returns the number of data bits that can be stored in a QR Code of the given version number, after
450 // all function modules are excluded. This includes remainder bits, so it might not be a multiple of 8.
451 // The result is in the range [208, 29648]. This could be implemented as a 40-entry lookup table.
452 private: static int getNumRawDataModules(int ver);
455 // Returns the number of 8-bit data (i.e. not error correction) codewords contained in any
456 // QR Code of the given version number and error correction level, with remainder bits discarded.
457 // This stateless pure function could be implemented as a (40*4)-cell lookup table.
458 private: static int getNumDataCodewords(int ver, Ecc ecl);
461 // Returns a Reed-Solomon ECC generator polynomial for the given degree. This could be
462 // implemented as a lookup table over all possible parameter values, instead of as an algorithm.
463 private: static std::vector<std::uint8_t> reedSolomonComputeDivisor(int degree);
466 // Returns the Reed-Solomon error correction codeword for the given data and divisor polynomials.
467 private: static std::vector<std::uint8_t> reedSolomonComputeRemainder(const std::vector<std::uint8_t> &data, const std::vector<std::uint8_t> &divisor);
470 // Returns the product of the two given field elements modulo GF(2^8/0x11D).
471 // All inputs are valid. This could be implemented as a 256*256 lookup table.
472 private: static std::uint8_t reedSolomonMultiply(std::uint8_t x, std::uint8_t y);
475 // Can only be called immediately after a white run is added, and
476 // returns either 0, 1, or 2. A helper function for getPenaltyScore().
477 private: int finderPenaltyCountPatterns(const std::array<int,7> &runHistory) const;
480 // Must be called at the end of a line (row or column) of modules. A helper function for getPenaltyScore().
481 private: int finderPenaltyTerminateAndCount(bool currentRunColor, int currentRunLength, std::array<int,7> &runHistory) const;
484 // Pushes the given value to the front and drops the last value. A helper function for getPenaltyScore().
485 private: void finderPenaltyAddHistory(int currentRunLength, std::array<int,7> &runHistory) const;
488 // Returns true iff the i'th bit of x is set to 1.
489 private: static bool getBit(long x, int i);
492 /*---- Constants and tables ----*/
494 // The minimum version number supported in the QR Code Model 2 standard.
495 public: static constexpr int MIN_VERSION = 1;
497 // The maximum version number supported in the QR Code Model 2 standard.
498 public: static constexpr int MAX_VERSION = 40;
501 // For use in getPenaltyScore(), when evaluating which mask is best.
502 private: static const int PENALTY_N1;
503 private: static const int PENALTY_N2;
504 private: static const int PENALTY_N3;
505 private: static const int PENALTY_N4;
508 private: static const std::int8_t ECC_CODEWORDS_PER_BLOCK[4][41];
509 private: static const std::int8_t NUM_ERROR_CORRECTION_BLOCKS[4][41];
515 /*---- Public exception class ----*/
518 * Thrown when the supplied data does not fit any QR Code version. Ways to handle this exception include:
519 * - Decrease the error correction level if it was greater than Ecc::LOW.
520 * - If the encodeSegments() function was called with a maxVersion argument, then increase
521 * it if it was less than QrCode::MAX_VERSION. (This advice does not apply to the other
522 * factory functions because they search all versions up to QrCode::MAX_VERSION.)
523 * - Split the text data into better or optimal segments in order to reduce the number of bits required.
524 * - Change the text or binary data to be shorter.
525 * - Change the text to fit the character set of a particular segment mode (e.g. alphanumeric).
526 * - Propagate the error upward to the caller/user.
528 class data_too_long : public std::length_error {
530 public: explicit data_too_long(const std::string &msg);
537 * An appendable sequence of bits (0s and 1s). Mainly used by QrSegment.
539 class BitBuffer final : public std::vector<bool> {
541 /*---- Constructor ----*/
543 // Creates an empty bit buffer (length 0).
550 // Appends the given number of low-order bits of the given value
551 // to this buffer. Requires 0 <= len <= 31 and val < 2^len.
552 public: void appendBits(std::uint32_t val, int len);