2 * QR Code generator library (Java)
4 * Copyright (c) Project Nayuki. (MIT License)
5 * https://www.nayuki.io/page/qr-code-generator-library
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8 * this software and associated documentation files (the "Software"), to deal in
9 * the Software without restriction, including without limitation the rights to
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12 * subject to the following conditions:
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24 package io.nayuki.qrcodegen;
26 import java.awt.image.BufferedImage;
27 import java.util.Arrays;
28 import java.util.List;
29 import java.util.Objects;
33 * A QR Code symbol, which is a type of two-dimension barcode.
34 * Invented by Denso Wave and described in the ISO/IEC 18004 standard.
35 * <p>Instances of this class represent an immutable square grid of black and white cells.
36 * The class provides static factory functions to create a QR Code from text or binary data.
37 * The class covers the QR Code Model 2 specification, supporting all versions (sizes)
38 * from 1 to 40, all 4 error correction levels, and 4 character encoding modes.</p>
39 * <p>Ways to create a QR Code object:</p>
41 * <li><p>High level: Take the payload data and call {@link QrCode#encodeText(String,Ecc)}
42 * or {@link QrCode#encodeBinary(byte[],Ecc)}.</p></li>
43 * <li><p>Mid level: Custom-make the list of {@link QrSegment segments}
44 * and call {@link QrCode#encodeSegments(List,Ecc)} or
45 * {@link QrCode#encodeSegments(List,Ecc,int,int,int,boolean)}</p></li>
46 * <li><p>Low level: Custom-make the array of data codeword bytes (including segment headers and
47 * final padding, excluding error correction codewords), supply the appropriate version number,
48 * and call the {@link QrCode#QrCode(int,Ecc,byte[],int) constructor}.</p></li>
50 * <p>(Note that all ways require supplying the desired error correction level.)</p>
53 public final class QrCode {
55 /*---- Static factory functions (high level) ----*/
58 * Returns a QR Code representing the specified Unicode text string at the specified error correction level.
59 * As a conservative upper bound, this function is guaranteed to succeed for strings that have 738 or fewer
60 * Unicode code points (not UTF-16 code units) if the low error correction level is used. The smallest possible
61 * QR Code version is automatically chosen for the output. The ECC level of the result may be higher than the
62 * ecl argument if it can be done without increasing the version.
63 * @param text the text to be encoded (not {@code null}), which can be any Unicode string
64 * @param ecl the error correction level to use (not {@code null}) (boostable)
65 * @return a QR Code (not {@code null}) representing the text
66 * @throws NullPointerException if the text or error correction level is {@code null}
67 * @throws DataTooLongException if the text fails to fit in the
68 * largest version QR Code at the ECL, which means it is too long
70 public static QrCode encodeText(String text, Ecc ecl) {
71 Objects.requireNonNull(text);
72 Objects.requireNonNull(ecl);
73 List<QrSegment> segs = QrSegment.makeSegments(text);
74 return encodeSegments(segs, ecl);
79 * Returns a QR Code representing the specified binary data at the specified error correction level.
80 * This function always encodes using the binary segment mode, not any text mode. The maximum number of
81 * bytes allowed is 2953. The smallest possible QR Code version is automatically chosen for the output.
82 * The ECC level of the result may be higher than the ecl argument if it can be done without increasing the version.
83 * @param data the binary data to encode (not {@code null})
84 * @param ecl the error correction level to use (not {@code null}) (boostable)
85 * @return a QR Code (not {@code null}) representing the data
86 * @throws NullPointerException if the data or error correction level is {@code null}
87 * @throws DataTooLongException if the data fails to fit in the
88 * largest version QR Code at the ECL, which means it is too long
90 public static QrCode encodeBinary(byte[] data, Ecc ecl) {
91 Objects.requireNonNull(data);
92 Objects.requireNonNull(ecl);
93 QrSegment seg = QrSegment.makeBytes(data);
94 return encodeSegments(Arrays.asList(seg), ecl);
98 /*---- Static factory functions (mid level) ----*/
101 * Returns a QR Code representing the specified segments at the specified error correction
102 * level. The smallest possible QR Code version is automatically chosen for the output. The ECC level
103 * of the result may be higher than the ecl argument if it can be done without increasing the version.
104 * <p>This function allows the user to create a custom sequence of segments that switches
105 * between modes (such as alphanumeric and byte) to encode text in less space.
106 * This is a mid-level API; the high-level API is {@link #encodeText(String,Ecc)}
107 * and {@link #encodeBinary(byte[],Ecc)}.</p>
108 * @param segs the segments to encode
109 * @param ecl the error correction level to use (not {@code null}) (boostable)
110 * @return a QR Code (not {@code null}) representing the segments
111 * @throws NullPointerException if the list of segments, any segment, or the error correction level is {@code null}
112 * @throws DataTooLongException if the segments fail to fit in the
113 * largest version QR Code at the ECL, which means they are too long
115 public static QrCode encodeSegments(List<QrSegment> segs, Ecc ecl) {
116 return encodeSegments(segs, ecl, MIN_VERSION, MAX_VERSION, -1, true);
121 * Returns a QR Code representing the specified segments with the specified encoding parameters.
122 * The smallest possible QR Code version within the specified range is automatically
123 * chosen for the output. Iff boostEcl is {@code true}, then the ECC level of the
124 * result may be higher than the ecl argument if it can be done without increasing
125 * the version. The mask number is either between 0 to 7 (inclusive) to force that
126 * mask, or −1 to automatically choose an appropriate mask (which may be slow).
127 * <p>This function allows the user to create a custom sequence of segments that switches
128 * between modes (such as alphanumeric and byte) to encode text in less space.
129 * This is a mid-level API; the high-level API is {@link #encodeText(String,Ecc)}
130 * and {@link #encodeBinary(byte[],Ecc)}.</p>
131 * @param segs the segments to encode
132 * @param ecl the error correction level to use (not {@code null}) (boostable)
133 * @param minVersion the minimum allowed version of the QR Code (at least 1)
134 * @param maxVersion the maximum allowed version of the QR Code (at most 40)
135 * @param mask the mask number to use (between 0 and 7 (inclusive)), or −1 for automatic mask
136 * @param boostEcl increases the ECC level as long as it doesn't increase the version number
137 * @return a QR Code (not {@code null}) representing the segments
138 * @throws NullPointerException if the list of segments, any segment, or the error correction level is {@code null}
139 * @throws IllegalArgumentException if 1 ≤ minVersion ≤ maxVersion ≤ 40
140 * or −1 ≤ mask ≤ 7 is violated
141 * @throws DataTooLongException if the segments fail to fit in
142 * the maxVersion QR Code at the ECL, which means they are too long
144 public static QrCode encodeSegments(List<QrSegment> segs, Ecc ecl, int minVersion, int maxVersion, int mask, boolean boostEcl) {
145 Objects.requireNonNull(segs);
146 Objects.requireNonNull(ecl);
147 if (!(MIN_VERSION <= minVersion && minVersion <= maxVersion && maxVersion <= MAX_VERSION) || mask < -1 || mask > 7)
148 throw new IllegalArgumentException("Invalid value");
150 // Find the minimal version number to use
151 int version, dataUsedBits;
152 for (version = minVersion; ; version++) {
153 int dataCapacityBits = getNumDataCodewords(version, ecl) * 8; // Number of data bits available
154 dataUsedBits = QrSegment.getTotalBits(segs, version);
155 if (dataUsedBits != -1 && dataUsedBits <= dataCapacityBits)
156 break; // This version number is found to be suitable
157 if (version >= maxVersion) { // All versions in the range could not fit the given data
158 String msg = "Segment too long";
159 if (dataUsedBits != -1)
160 msg = String.format("Data length = %d bits, Max capacity = %d bits", dataUsedBits, dataCapacityBits);
161 throw new DataTooLongException(msg);
164 assert dataUsedBits != -1;
166 // Increase the error correction level while the data still fits in the current version number
167 for (Ecc newEcl : Ecc.values()) { // From low to high
168 if (boostEcl && dataUsedBits <= getNumDataCodewords(version, newEcl) * 8)
172 // Concatenate all segments to create the data bit string
173 BitBuffer bb = new BitBuffer();
174 for (QrSegment seg : segs) {
175 bb.appendBits(seg.mode.modeBits, 4);
176 bb.appendBits(seg.numChars, seg.mode.numCharCountBits(version));
177 bb.appendData(seg.data);
179 assert bb.bitLength() == dataUsedBits;
181 // Add terminator and pad up to a byte if applicable
182 int dataCapacityBits = getNumDataCodewords(version, ecl) * 8;
183 assert bb.bitLength() <= dataCapacityBits;
184 bb.appendBits(0, Math.min(4, dataCapacityBits - bb.bitLength()));
185 bb.appendBits(0, (8 - bb.bitLength() % 8) % 8);
186 assert bb.bitLength() % 8 == 0;
188 // Pad with alternating bytes until data capacity is reached
189 for (int padByte = 0xEC; bb.bitLength() < dataCapacityBits; padByte ^= 0xEC ^ 0x11)
190 bb.appendBits(padByte, 8);
192 // Pack bits into bytes in big endian
193 byte[] dataCodewords = new byte[bb.bitLength() / 8];
194 for (int i = 0; i < bb.bitLength(); i++)
195 dataCodewords[i >>> 3] |= bb.getBit(i) << (7 - (i & 7));
197 // Create the QR Code object
198 return new QrCode(version, ecl, dataCodewords, mask);
203 /*---- Instance fields ----*/
205 // Public immutable scalar parameters:
207 /** The version number of this QR Code, which is between 1 and 40 (inclusive).
208 * This determines the size of this barcode. */
209 public final int version;
211 /** The width and height of this QR Code, measured in modules, between
212 * 21 and 177 (inclusive). This is equal to version × 4 + 17. */
213 public final int size;
215 /** The error correction level used in this QR Code, which is not {@code null}. */
216 public final Ecc errorCorrectionLevel;
218 /** The index of the mask pattern used in this QR Code, which is between 0 and 7 (inclusive).
219 * <p>Even if a QR Code is created with automatic masking requested (mask =
220 * −1), the resulting object still has a mask value between 0 and 7. */
221 public final int mask;
223 // Private grids of modules/pixels, with dimensions of size*size:
225 // The modules of this QR Code (false = white, true = black).
226 // Immutable after constructor finishes. Accessed through getModule().
227 private boolean[][] modules;
229 // Indicates function modules that are not subjected to masking. Discarded when constructor finishes.
230 private boolean[][] isFunction;
234 /*---- Constructor (low level) ----*/
237 * Constructs a QR Code with the specified version number,
238 * error correction level, data codeword bytes, and mask number.
239 * <p>This is a low-level API that most users should not use directly. A mid-level
240 * API is the {@link #encodeSegments(List,Ecc,int,int,int,boolean)} function.</p>
241 * @param ver the version number to use, which must be in the range 1 to 40 (inclusive)
242 * @param ecl the error correction level to use
243 * @param dataCodewords the bytes representing segments to encode (without ECC)
244 * @param msk the mask pattern to use, which is either −1 for automatic choice or from 0 to 7 for fixed choice
245 * @throws NullPointerException if the byte array or error correction level is {@code null}
246 * @throws IllegalArgumentException if the version or mask value is out of range,
247 * or if the data is the wrong length for the specified version and error correction level
249 public QrCode(int ver, Ecc ecl, byte[] dataCodewords, int msk) {
250 // Check arguments and initialize fields
251 if (ver < MIN_VERSION || ver > MAX_VERSION)
252 throw new IllegalArgumentException("Version value out of range");
253 if (msk < -1 || msk > 7)
254 throw new IllegalArgumentException("Mask value out of range");
257 errorCorrectionLevel = Objects.requireNonNull(ecl);
258 Objects.requireNonNull(dataCodewords);
259 modules = new boolean[size][size]; // Initially all white
260 isFunction = new boolean[size][size];
262 // Compute ECC, draw modules, do masking
263 drawFunctionPatterns();
264 byte[] allCodewords = addEccAndInterleave(dataCodewords);
265 drawCodewords(allCodewords);
266 this.mask = handleConstructorMasking(msk);
272 /*---- Public instance methods ----*/
275 * Returns the color of the module (pixel) at the specified coordinates, which is {@code false}
276 * for white or {@code true} for black. The top left corner has the coordinates (x=0, y=0).
277 * If the specified coordinates are out of bounds, then {@code false} (white) is returned.
278 * @param x the x coordinate, where 0 is the left edge and size−1 is the right edge
279 * @param y the y coordinate, where 0 is the top edge and size−1 is the bottom edge
280 * @return {@code true} if the coordinates are in bounds and the module
281 * at that location is black, or {@code false} (white) otherwise
283 public boolean getModule(int x, int y) {
284 return 0 <= x && x < size && 0 <= y && y < size && modules[y][x];
289 * Returns a raster image depicting this QR Code, with the specified module scale and border modules.
290 * <p>For example, toImage(scale=10, border=4) means to pad the QR Code with 4 white
291 * border modules on all four sides, and use 10×10 pixels to represent each module.
292 * The resulting image only contains the hex colors 000000 and FFFFFF.
293 * @param scale the side length (measured in pixels, must be positive) of each module
294 * @param border the number of border modules to add, which must be non-negative
295 * @return a new image representing this QR Code, with padding and scaling
296 * @throws IllegalArgumentException if the scale or border is out of range, or if
297 * {scale, border, size} cause the image dimensions to exceed Integer.MAX_VALUE
299 public BufferedImage toImage(int scale, int border) {
300 if (scale <= 0 || border < 0)
301 throw new IllegalArgumentException("Value out of range");
302 if (border > Integer.MAX_VALUE / 2 || size + border * 2L > Integer.MAX_VALUE / scale)
303 throw new IllegalArgumentException("Scale or border too large");
305 BufferedImage result = new BufferedImage((size + border * 2) * scale, (size + border * 2) * scale, BufferedImage.TYPE_INT_RGB);
306 for (int y = 0; y < result.getHeight(); y++) {
307 for (int x = 0; x < result.getWidth(); x++) {
308 boolean color = getModule(x / scale - border, y / scale - border);
309 result.setRGB(x, y, color ? 0x000000 : 0xFFFFFF);
317 * Returns a string of SVG code for an image depicting this QR Code, with the specified number
318 * of border modules. The string always uses Unix newlines (\n), regardless of the platform.
319 * @param border the number of border modules to add, which must be non-negative
320 * @return a string representing this QR Code as an SVG XML document
321 * @throws IllegalArgumentException if the border is negative
323 public String toSvgString(int border) {
325 throw new IllegalArgumentException("Border must be non-negative");
327 StringBuilder sb = new StringBuilder()
328 .append("<?xml version=\"1.0\" encoding=\"UTF-8\"?>\n")
329 .append("<!DOCTYPE svg PUBLIC \"-//W3C//DTD SVG 1.1//EN\" \"http://www.w3.org/Graphics/SVG/1.1/DTD/svg11.dtd\">\n")
330 .append(String.format("<svg xmlns=\"http://www.w3.org/2000/svg\" version=\"1.1\" viewBox=\"0 0 %1$d %1$d\" stroke=\"none\">\n",
332 .append("\t<rect width=\"100%\" height=\"100%\" fill=\"#FFFFFF\"/>\n")
333 .append("\t<path d=\"");
334 for (int y = 0; y < size; y++) {
335 for (int x = 0; x < size; x++) {
336 if (getModule(x, y)) {
337 if (x != 0 || y != 0)
339 sb.append(String.format("M%d,%dh1v1h-1z", x + brd, y + brd));
344 .append("\" fill=\"#000000\"/>\n")
351 /*---- Private helper methods for constructor: Drawing function modules ----*/
353 // Reads this object's version field, and draws and marks all function modules.
354 private void drawFunctionPatterns() {
355 // Draw horizontal and vertical timing patterns
356 for (int i = 0; i < size; i++) {
357 setFunctionModule(6, i, i % 2 == 0);
358 setFunctionModule(i, 6, i % 2 == 0);
361 // Draw 3 finder patterns (all corners except bottom right; overwrites some timing modules)
362 drawFinderPattern(3, 3);
363 drawFinderPattern(size - 4, 3);
364 drawFinderPattern(3, size - 4);
366 // Draw numerous alignment patterns
367 int[] alignPatPos = getAlignmentPatternPositions();
368 int numAlign = alignPatPos.length;
369 for (int i = 0; i < numAlign; i++) {
370 for (int j = 0; j < numAlign; j++) {
371 // Don't draw on the three finder corners
372 if (!(i == 0 && j == 0 || i == 0 && j == numAlign - 1 || i == numAlign - 1 && j == 0))
373 drawAlignmentPattern(alignPatPos[i], alignPatPos[j]);
377 // Draw configuration data
378 drawFormatBits(0); // Dummy mask value; overwritten later in the constructor
383 // Draws two copies of the format bits (with its own error correction code)
384 // based on the given mask and this object's error correction level field.
385 private void drawFormatBits(int msk) {
386 // Calculate error correction code and pack bits
387 int data = errorCorrectionLevel.formatBits << 3 | msk; // errCorrLvl is uint2, mask is uint3
389 for (int i = 0; i < 10; i++)
390 rem = (rem << 1) ^ ((rem >>> 9) * 0x537);
391 int bits = (data << 10 | rem) ^ 0x5412; // uint15
392 assert bits >>> 15 == 0;
395 for (int i = 0; i <= 5; i++)
396 setFunctionModule(8, i, getBit(bits, i));
397 setFunctionModule(8, 7, getBit(bits, 6));
398 setFunctionModule(8, 8, getBit(bits, 7));
399 setFunctionModule(7, 8, getBit(bits, 8));
400 for (int i = 9; i < 15; i++)
401 setFunctionModule(14 - i, 8, getBit(bits, i));
404 for (int i = 0; i < 8; i++)
405 setFunctionModule(size - 1 - i, 8, getBit(bits, i));
406 for (int i = 8; i < 15; i++)
407 setFunctionModule(8, size - 15 + i, getBit(bits, i));
408 setFunctionModule(8, size - 8, true); // Always black
412 // Draws two copies of the version bits (with its own error correction code),
413 // based on this object's version field, iff 7 <= version <= 40.
414 private void drawVersion() {
418 // Calculate error correction code and pack bits
419 int rem = version; // version is uint6, in the range [7, 40]
420 for (int i = 0; i < 12; i++)
421 rem = (rem << 1) ^ ((rem >>> 11) * 0x1F25);
422 int bits = version << 12 | rem; // uint18
423 assert bits >>> 18 == 0;
426 for (int i = 0; i < 18; i++) {
427 boolean bit = getBit(bits, i);
428 int a = size - 11 + i % 3;
430 setFunctionModule(a, b, bit);
431 setFunctionModule(b, a, bit);
436 // Draws a 9*9 finder pattern including the border separator,
437 // with the center module at (x, y). Modules can be out of bounds.
438 private void drawFinderPattern(int x, int y) {
439 for (int dy = -4; dy <= 4; dy++) {
440 for (int dx = -4; dx <= 4; dx++) {
441 int dist = Math.max(Math.abs(dx), Math.abs(dy)); // Chebyshev/infinity norm
442 int xx = x + dx, yy = y + dy;
443 if (0 <= xx && xx < size && 0 <= yy && yy < size)
444 setFunctionModule(xx, yy, dist != 2 && dist != 4);
450 // Draws a 5*5 alignment pattern, with the center module
451 // at (x, y). All modules must be in bounds.
452 private void drawAlignmentPattern(int x, int y) {
453 for (int dy = -2; dy <= 2; dy++) {
454 for (int dx = -2; dx <= 2; dx++)
455 setFunctionModule(x + dx, y + dy, Math.max(Math.abs(dx), Math.abs(dy)) != 1);
460 // Sets the color of a module and marks it as a function module.
461 // Only used by the constructor. Coordinates must be in bounds.
462 private void setFunctionModule(int x, int y, boolean isBlack) {
463 modules[y][x] = isBlack;
464 isFunction[y][x] = true;
468 /*---- Private helper methods for constructor: Codewords and masking ----*/
470 // Returns a new byte string representing the given data with the appropriate error correction
471 // codewords appended to it, based on this object's version and error correction level.
472 private byte[] addEccAndInterleave(byte[] data) {
473 Objects.requireNonNull(data);
474 if (data.length != getNumDataCodewords(version, errorCorrectionLevel))
475 throw new IllegalArgumentException();
477 // Calculate parameter numbers
478 int numBlocks = NUM_ERROR_CORRECTION_BLOCKS[errorCorrectionLevel.ordinal()][version];
479 int blockEccLen = ECC_CODEWORDS_PER_BLOCK [errorCorrectionLevel.ordinal()][version];
480 int rawCodewords = getNumRawDataModules(version) / 8;
481 int numShortBlocks = numBlocks - rawCodewords % numBlocks;
482 int shortBlockLen = rawCodewords / numBlocks;
484 // Split data into blocks and append ECC to each block
485 byte[][] blocks = new byte[numBlocks][];
486 byte[] rsDiv = reedSolomonComputeDivisor(blockEccLen);
487 for (int i = 0, k = 0; i < numBlocks; i++) {
488 byte[] dat = Arrays.copyOfRange(data, k, k + shortBlockLen - blockEccLen + (i < numShortBlocks ? 0 : 1));
490 byte[] block = Arrays.copyOf(dat, shortBlockLen + 1);
491 byte[] ecc = reedSolomonComputeRemainder(dat, rsDiv);
492 System.arraycopy(ecc, 0, block, block.length - blockEccLen, ecc.length);
496 // Interleave (not concatenate) the bytes from every block into a single sequence
497 byte[] result = new byte[rawCodewords];
498 for (int i = 0, k = 0; i < blocks[0].length; i++) {
499 for (int j = 0; j < blocks.length; j++) {
500 // Skip the padding byte in short blocks
501 if (i != shortBlockLen - blockEccLen || j >= numShortBlocks) {
502 result[k] = blocks[j][i];
511 // Draws the given sequence of 8-bit codewords (data and error correction) onto the entire
512 // data area of this QR Code. Function modules need to be marked off before this is called.
513 private void drawCodewords(byte[] data) {
514 Objects.requireNonNull(data);
515 if (data.length != getNumRawDataModules(version) / 8)
516 throw new IllegalArgumentException();
518 int i = 0; // Bit index into the data
519 // Do the funny zigzag scan
520 for (int right = size - 1; right >= 1; right -= 2) { // Index of right column in each column pair
523 for (int vert = 0; vert < size; vert++) { // Vertical counter
524 for (int j = 0; j < 2; j++) {
525 int x = right - j; // Actual x coordinate
526 boolean upward = ((right + 1) & 2) == 0;
527 int y = upward ? size - 1 - vert : vert; // Actual y coordinate
528 if (!isFunction[y][x] && i < data.length * 8) {
529 modules[y][x] = getBit(data[i >>> 3], 7 - (i & 7));
532 // If this QR Code has any remainder bits (0 to 7), they were assigned as
533 // 0/false/white by the constructor and are left unchanged by this method
537 assert i == data.length * 8;
541 // XORs the codeword modules in this QR Code with the given mask pattern.
542 // The function modules must be marked and the codeword bits must be drawn
543 // before masking. Due to the arithmetic of XOR, calling applyMask() with
544 // the same mask value a second time will undo the mask. A final well-formed
545 // QR Code needs exactly one (not zero, two, etc.) mask applied.
546 private void applyMask(int msk) {
547 if (msk < 0 || msk > 7)
548 throw new IllegalArgumentException("Mask value out of range");
549 for (int y = 0; y < size; y++) {
550 for (int x = 0; x < size; x++) {
553 case 0: invert = (x + y) % 2 == 0; break;
554 case 1: invert = y % 2 == 0; break;
555 case 2: invert = x % 3 == 0; break;
556 case 3: invert = (x + y) % 3 == 0; break;
557 case 4: invert = (x / 3 + y / 2) % 2 == 0; break;
558 case 5: invert = x * y % 2 + x * y % 3 == 0; break;
559 case 6: invert = (x * y % 2 + x * y % 3) % 2 == 0; break;
560 case 7: invert = ((x + y) % 2 + x * y % 3) % 2 == 0; break;
561 default: throw new AssertionError();
563 modules[y][x] ^= invert & !isFunction[y][x];
569 // A messy helper function for the constructor. This QR Code must be in an unmasked state when this
570 // method is called. The given argument is the requested mask, which is -1 for auto or 0 to 7 for fixed.
571 // This method applies and returns the actual mask chosen, from 0 to 7.
572 private int handleConstructorMasking(int msk) {
573 if (msk == -1) { // Automatically choose best mask
574 int minPenalty = Integer.MAX_VALUE;
575 for (int i = 0; i < 8; i++) {
578 int penalty = getPenaltyScore();
579 if (penalty < minPenalty) {
581 minPenalty = penalty;
583 applyMask(i); // Undoes the mask due to XOR
586 assert 0 <= msk && msk <= 7;
587 applyMask(msk); // Apply the final choice of mask
588 drawFormatBits(msk); // Overwrite old format bits
589 return msk; // The caller shall assign this value to the final-declared field
593 // Calculates and returns the penalty score based on state of this QR Code's current modules.
594 // This is used by the automatic mask choice algorithm to find the mask pattern that yields the lowest score.
595 private int getPenaltyScore() {
598 // Adjacent modules in row having same color, and finder-like patterns
599 for (int y = 0; y < size; y++) {
600 boolean runColor = false;
602 int[] runHistory = new int[7];
603 for (int x = 0; x < size; x++) {
604 if (modules[y][x] == runColor) {
607 result += PENALTY_N1;
611 finderPenaltyAddHistory(runX, runHistory);
613 result += finderPenaltyCountPatterns(runHistory) * PENALTY_N3;
614 runColor = modules[y][x];
618 result += finderPenaltyTerminateAndCount(runColor, runX, runHistory) * PENALTY_N3;
620 // Adjacent modules in column having same color, and finder-like patterns
621 for (int x = 0; x < size; x++) {
622 boolean runColor = false;
624 int[] runHistory = new int[7];
625 for (int y = 0; y < size; y++) {
626 if (modules[y][x] == runColor) {
629 result += PENALTY_N1;
633 finderPenaltyAddHistory(runY, runHistory);
635 result += finderPenaltyCountPatterns(runHistory) * PENALTY_N3;
636 runColor = modules[y][x];
640 result += finderPenaltyTerminateAndCount(runColor, runY, runHistory) * PENALTY_N3;
643 // 2*2 blocks of modules having same color
644 for (int y = 0; y < size - 1; y++) {
645 for (int x = 0; x < size - 1; x++) {
646 boolean color = modules[y][x];
647 if ( color == modules[y][x + 1] &&
648 color == modules[y + 1][x] &&
649 color == modules[y + 1][x + 1])
650 result += PENALTY_N2;
654 // Balance of black and white modules
656 for (boolean[] row : modules) {
657 for (boolean color : row) {
662 int total = size * size; // Note that size is odd, so black/total != 1/2
663 // Compute the smallest integer k >= 0 such that (45-5k)% <= black/total <= (55+5k)%
664 int k = (Math.abs(black * 20 - total * 10) + total - 1) / total - 1;
665 result += k * PENALTY_N4;
671 /*---- Private helper functions ----*/
673 // Returns an ascending list of positions of alignment patterns for this version number.
674 // Each position is in the range [0,177), and are used on both the x and y axes.
675 // This could be implemented as lookup table of 40 variable-length lists of unsigned bytes.
676 private int[] getAlignmentPatternPositions() {
680 int numAlign = version / 7 + 2;
682 if (version == 32) // Special snowflake
684 else // step = ceil[(size - 13) / (numAlign*2 - 2)] * 2
685 step = (version*4 + numAlign*2 + 1) / (numAlign*2 - 2) * 2;
686 int[] result = new int[numAlign];
688 for (int i = result.length - 1, pos = size - 7; i >= 1; i--, pos -= step)
695 // Returns the number of data bits that can be stored in a QR Code of the given version number, after
696 // all function modules are excluded. This includes remainder bits, so it might not be a multiple of 8.
697 // The result is in the range [208, 29648]. This could be implemented as a 40-entry lookup table.
698 private static int getNumRawDataModules(int ver) {
699 if (ver < MIN_VERSION || ver > MAX_VERSION)
700 throw new IllegalArgumentException("Version number out of range");
702 int size = ver * 4 + 17;
703 int result = size * size; // Number of modules in the whole QR Code square
704 result -= 8 * 8 * 3; // Subtract the three finders with separators
705 result -= 15 * 2 + 1; // Subtract the format information and black module
706 result -= (size - 16) * 2; // Subtract the timing patterns (excluding finders)
707 // The five lines above are equivalent to: int result = (16 * ver + 128) * ver + 64;
709 int numAlign = ver / 7 + 2;
710 result -= (numAlign - 1) * (numAlign - 1) * 25; // Subtract alignment patterns not overlapping with timing patterns
711 result -= (numAlign - 2) * 2 * 20; // Subtract alignment patterns that overlap with timing patterns
712 // The two lines above are equivalent to: result -= (25 * numAlign - 10) * numAlign - 55;
714 result -= 6 * 3 * 2; // Subtract version information
716 assert 208 <= result && result <= 29648;
721 // Returns a Reed-Solomon ECC generator polynomial for the given degree. This could be
722 // implemented as a lookup table over all possible parameter values, instead of as an algorithm.
723 private static byte[] reedSolomonComputeDivisor(int degree) {
724 if (degree < 1 || degree > 255)
725 throw new IllegalArgumentException("Degree out of range");
726 // Polynomial coefficients are stored from highest to lowest power, excluding the leading term which is always 1.
727 // For example the polynomial x^3 + 255x^2 + 8x + 93 is stored as the uint8 array {255, 8, 93}.
728 byte[] result = new byte[degree];
729 result[degree - 1] = 1; // Start off with the monomial x^0
731 // Compute the product polynomial (x - r^0) * (x - r^1) * (x - r^2) * ... * (x - r^{degree-1}),
732 // and drop the highest monomial term which is always 1x^degree.
733 // Note that r = 0x02, which is a generator element of this field GF(2^8/0x11D).
735 for (int i = 0; i < degree; i++) {
736 // Multiply the current product by (x - r^i)
737 for (int j = 0; j < result.length; j++) {
738 result[j] = (byte)reedSolomonMultiply(result[j] & 0xFF, root);
739 if (j + 1 < result.length)
740 result[j] ^= result[j + 1];
742 root = reedSolomonMultiply(root, 0x02);
748 // Returns the Reed-Solomon error correction codeword for the given data and divisor polynomials.
749 private static byte[] reedSolomonComputeRemainder(byte[] data, byte[] divisor) {
750 Objects.requireNonNull(data);
751 Objects.requireNonNull(divisor);
752 byte[] result = new byte[divisor.length];
753 for (byte b : data) { // Polynomial division
754 int factor = (b ^ result[0]) & 0xFF;
755 System.arraycopy(result, 1, result, 0, result.length - 1);
756 result[result.length - 1] = 0;
757 for (int i = 0; i < result.length; i++)
758 result[i] ^= reedSolomonMultiply(divisor[i] & 0xFF, factor);
764 // Returns the product of the two given field elements modulo GF(2^8/0x11D). The arguments and result
765 // are unsigned 8-bit integers. This could be implemented as a lookup table of 256*256 entries of uint8.
766 private static int reedSolomonMultiply(int x, int y) {
767 assert x >> 8 == 0 && y >> 8 == 0;
768 // Russian peasant multiplication
770 for (int i = 7; i >= 0; i--) {
771 z = (z << 1) ^ ((z >>> 7) * 0x11D);
772 z ^= ((y >>> i) & 1) * x;
779 // Returns the number of 8-bit data (i.e. not error correction) codewords contained in any
780 // QR Code of the given version number and error correction level, with remainder bits discarded.
781 // This stateless pure function could be implemented as a (40*4)-cell lookup table.
782 static int getNumDataCodewords(int ver, Ecc ecl) {
783 return getNumRawDataModules(ver) / 8
784 - ECC_CODEWORDS_PER_BLOCK [ecl.ordinal()][ver]
785 * NUM_ERROR_CORRECTION_BLOCKS[ecl.ordinal()][ver];
789 // Can only be called immediately after a white run is added, and
790 // returns either 0, 1, or 2. A helper function for getPenaltyScore().
791 private int finderPenaltyCountPatterns(int[] runHistory) {
792 int n = runHistory[1];
793 assert n <= size * 3;
794 boolean core = n > 0 && runHistory[2] == n && runHistory[3] == n * 3 && runHistory[4] == n && runHistory[5] == n;
795 return (core && runHistory[0] >= n * 4 && runHistory[6] >= n ? 1 : 0)
796 + (core && runHistory[6] >= n * 4 && runHistory[0] >= n ? 1 : 0);
800 // Must be called at the end of a line (row or column) of modules. A helper function for getPenaltyScore().
801 private int finderPenaltyTerminateAndCount(boolean currentRunColor, int currentRunLength, int[] runHistory) {
802 if (currentRunColor) { // Terminate black run
803 finderPenaltyAddHistory(currentRunLength, runHistory);
804 currentRunLength = 0;
806 currentRunLength += size; // Add white border to final run
807 finderPenaltyAddHistory(currentRunLength, runHistory);
808 return finderPenaltyCountPatterns(runHistory);
812 // Pushes the given value to the front and drops the last value. A helper function for getPenaltyScore().
813 private void finderPenaltyAddHistory(int currentRunLength, int[] runHistory) {
814 if (runHistory[0] == 0)
815 currentRunLength += size; // Add white border to initial run
816 System.arraycopy(runHistory, 0, runHistory, 1, runHistory.length - 1);
817 runHistory[0] = currentRunLength;
821 // Returns true iff the i'th bit of x is set to 1.
822 static boolean getBit(int x, int i) {
823 return ((x >>> i) & 1) != 0;
827 /*---- Constants and tables ----*/
829 /** The minimum version number (1) supported in the QR Code Model 2 standard. */
830 public static final int MIN_VERSION = 1;
832 /** The maximum version number (40) supported in the QR Code Model 2 standard. */
833 public static final int MAX_VERSION = 40;
836 // For use in getPenaltyScore(), when evaluating which mask is best.
837 private static final int PENALTY_N1 = 3;
838 private static final int PENALTY_N2 = 3;
839 private static final int PENALTY_N3 = 40;
840 private static final int PENALTY_N4 = 10;
843 private static final byte[][] ECC_CODEWORDS_PER_BLOCK = {
844 // Version: (note that index 0 is for padding, and is set to an illegal value)
845 //0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40 Error correction level
846 {-1, 7, 10, 15, 20, 26, 18, 20, 24, 30, 18, 20, 24, 26, 30, 22, 24, 28, 30, 28, 28, 28, 28, 30, 30, 26, 28, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30}, // Low
847 {-1, 10, 16, 26, 18, 24, 16, 18, 22, 22, 26, 30, 22, 22, 24, 24, 28, 28, 26, 26, 26, 26, 28, 28, 28, 28, 28, 28, 28, 28, 28, 28, 28, 28, 28, 28, 28, 28, 28, 28, 28}, // Medium
848 {-1, 13, 22, 18, 26, 18, 24, 18, 22, 20, 24, 28, 26, 24, 20, 30, 24, 28, 28, 26, 30, 28, 30, 30, 30, 30, 28, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30}, // Quartile
849 {-1, 17, 28, 22, 16, 22, 28, 26, 26, 24, 28, 24, 28, 22, 24, 24, 30, 28, 28, 26, 28, 30, 24, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30}, // High
852 private static final byte[][] NUM_ERROR_CORRECTION_BLOCKS = {
853 // Version: (note that index 0 is for padding, and is set to an illegal value)
854 //0, 1, 2, 3, 4, 5, 6, 7, 8, 9,10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40 Error correction level
855 {-1, 1, 1, 1, 1, 1, 2, 2, 2, 2, 4, 4, 4, 4, 4, 6, 6, 6, 6, 7, 8, 8, 9, 9, 10, 12, 12, 12, 13, 14, 15, 16, 17, 18, 19, 19, 20, 21, 22, 24, 25}, // Low
856 {-1, 1, 1, 1, 2, 2, 4, 4, 4, 5, 5, 5, 8, 9, 9, 10, 10, 11, 13, 14, 16, 17, 17, 18, 20, 21, 23, 25, 26, 28, 29, 31, 33, 35, 37, 38, 40, 43, 45, 47, 49}, // Medium
857 {-1, 1, 1, 2, 2, 4, 4, 6, 6, 8, 8, 8, 10, 12, 16, 12, 17, 16, 18, 21, 20, 23, 23, 25, 27, 29, 34, 34, 35, 38, 40, 43, 45, 48, 51, 53, 56, 59, 62, 65, 68}, // Quartile
858 {-1, 1, 1, 2, 4, 4, 4, 5, 6, 8, 8, 11, 11, 16, 16, 18, 16, 19, 21, 25, 25, 25, 34, 30, 32, 35, 37, 40, 42, 45, 48, 51, 54, 57, 60, 63, 66, 70, 74, 77, 81}, // High
863 /*---- Public helper enumeration ----*/
866 * The error correction level in a QR Code symbol.
869 // Must be declared in ascending order of error protection
870 // so that the implicit ordinal() and values() work properly
871 /** The QR Code can tolerate about 7% erroneous codewords. */ LOW(1),
872 /** The QR Code can tolerate about 15% erroneous codewords. */ MEDIUM(0),
873 /** The QR Code can tolerate about 25% erroneous codewords. */ QUARTILE(3),
874 /** The QR Code can tolerate about 30% erroneous codewords. */ HIGH(2);
876 // In the range 0 to 3 (unsigned 2-bit integer).
877 final int formatBits;
880 private Ecc(int fb) {