Instances of this class represent an immutable square grid of dark and light cells. * The class provides static factory functions to create a QR Code from text or binary data. * The class covers the QR Code Model 2 specification, supporting all versions (sizes) * from 1 to 40, all 4 error correction levels, and 4 character encoding modes.
*Ways to create a QR Code object:
*High level: Take the payload data and call {@link QrCode#encodeText(String,Ecc)} * or {@link QrCode#encodeBinary(byte[],Ecc)}.
Mid level: Custom-make the list of {@link QrSegment segments} * and call {@link QrCode#encodeSegments(List,Ecc)} or * {@link QrCode#encodeSegments(List,Ecc,int,int,int,boolean)}
Low level: Custom-make the array of data codeword bytes (including segment headers and * final padding, excluding error correction codewords), supply the appropriate version number, * and call the {@link QrCode#QrCode(int,Ecc,byte[],int) constructor}.
(Note that all ways require supplying the desired error correction level.)
* @see QrSegment */ public final class QrCode { /*---- Static factory functions (high level) ----*/ /** * Returns a QR Code representing the specified Unicode text string at the specified error correction level. * As a conservative upper bound, this function is guaranteed to succeed for strings that have 738 or fewer * Unicode code points (not UTF-16 code units) if the low error correction level is used. The smallest possible * QR Code version is automatically chosen for the output. The ECC level of the result may be higher than the * ecl argument if it can be done without increasing the version. * @param text the text to be encoded (not {@code null}), which can be any Unicode string * @param ecl the error correction level to use (not {@code null}) (boostable) * @return a QR Code (not {@code null}) representing the text * @throws NullPointerException if the text or error correction level is {@code null} * @throws DataTooLongException if the text fails to fit in the * largest version QR Code at the ECL, which means it is too long */ public static QrCode encodeText(String text, Ecc ecl) { Objects.requireNonNull(text); Objects.requireNonNull(ecl); ListThis function allows the user to create a custom sequence of segments that switches * between modes (such as alphanumeric and byte) to encode text in less space. * This is a mid-level API; the high-level API is {@link #encodeText(String,Ecc)} * and {@link #encodeBinary(byte[],Ecc)}.
* @param segs the segments to encode * @param ecl the error correction level to use (not {@code null}) (boostable) * @return a QR Code (not {@code null}) representing the segments * @throws NullPointerException if the list of segments, any segment, or the error correction level is {@code null} * @throws DataTooLongException if the segments fail to fit in the * largest version QR Code at the ECL, which means they are too long */ public static QrCode encodeSegments(ListThis function allows the user to create a custom sequence of segments that switches * between modes (such as alphanumeric and byte) to encode text in less space. * This is a mid-level API; the high-level API is {@link #encodeText(String,Ecc)} * and {@link #encodeBinary(byte[],Ecc)}.
* @param segs the segments to encode * @param ecl the error correction level to use (not {@code null}) (boostable) * @param minVersion the minimum allowed version of the QR Code (at least 1) * @param maxVersion the maximum allowed version of the QR Code (at most 40) * @param mask the mask number to use (between 0 and 7 (inclusive)), or −1 for automatic mask * @param boostEcl increases the ECC level as long as it doesn't increase the version number * @return a QR Code (not {@code null}) representing the segments * @throws NullPointerException if the list of segments, any segment, or the error correction level is {@code null} * @throws IllegalArgumentException if 1 ≤ minVersion ≤ maxVersion ≤ 40 * or −1 ≤ mask ≤ 7 is violated * @throws DataTooLongException if the segments fail to fit in * the maxVersion QR Code at the ECL, which means they are too long */ public static QrCode encodeSegments(ListEven if a QR Code is created with automatic masking requested (mask = * −1), the resulting object still has a mask value between 0 and 7. */ public final int mask; // Private grid of modules of this QR Code, packed tightly into bits. // Immutable after constructor finishes. Accessed through getModule(). private final int[] modules; /*---- Constructor (low level) ----*/ /** * Constructs a QR Code with the specified version number, * error correction level, data codeword bytes, and mask number. *
This is a low-level API that most users should not use directly. A mid-level * API is the {@link #encodeSegments(List,Ecc,int,int,int,boolean)} function.
* @param ver the version number to use, which must be in the range 1 to 40 (inclusive) * @param ecl the error correction level to use * @param dataCodewords the bytes representing segments to encode (without ECC) * @param msk the mask pattern to use, which is either −1 for automatic choice or from 0 to 7 for fixed choice * @throws NullPointerException if the byte array or error correction level is {@code null} * @throws IllegalArgumentException if the version or mask value is out of range, * or if the data is the wrong length for the specified version and error correction level */ public QrCode(int ver, Ecc ecl, byte[] dataCodewords, int msk) { // Check arguments and initialize fields if (ver < MIN_VERSION || ver > MAX_VERSION) throw new IllegalArgumentException("Version value out of range"); if (msk < -1 || msk > 7) throw new IllegalArgumentException("Mask value out of range"); version = ver; size = ver * 4 + 17; errorCorrectionLevel = Objects.requireNonNull(ecl); Objects.requireNonNull(dataCodewords); QrTemplate tpl = QrTemplate.MEMOIZER.get(ver); modules = tpl.template.clone(); // Compute ECC, draw modules, do masking byte[] allCodewords = addEccAndInterleave(dataCodewords); drawCodewords(tpl.dataOutputBitIndexes, allCodewords); mask = handleConstructorMasking(tpl.masks, msk); } /*---- Public instance methods ----*/ /** * Returns the color of the module (pixel) at the specified coordinates, which is {@code false} * for light or {@code true} for dark. The top left corner has the coordinates (x=0, y=0). * If the specified coordinates are out of bounds, then {@code false} (light) is returned. * @param x the x coordinate, where 0 is the left edge and size−1 is the right edge * @param y the y coordinate, where 0 is the top edge and size−1 is the bottom edge * @return {@code true} if the coordinates are in bounds and the module * at that location is dark, or {@code false} (light) otherwise */ public boolean getModule(int x, int y) { if (0 <= x && x < size && 0 <= y && y < size) { int i = y * size + x; return getBit(modules[i >>> 5], i) != 0; } else return false; } /** * Returns a raster image depicting this QR Code, with the specified module scale and border modules. *For example, toImage(scale=10, border=4) means to pad the QR Code with 4 light * border modules on all four sides, and use 10×10 pixels to represent each module. * The resulting image only contains the hex colors 000000 and FFFFFF. * @param scale the side length (measured in pixels, must be positive) of each module * @param border the number of border modules to add, which must be non-negative * @return a new image representing this QR Code, with padding and scaling * @throws IllegalArgumentException if the scale or border is out of range, or if * {scale, border, size} cause the image dimensions to exceed Integer.MAX_VALUE */ public BufferedImage toImage(int scale, int border) { if (scale <= 0 || border < 0) throw new IllegalArgumentException("Value out of range"); if (border > Integer.MAX_VALUE / 2 || size + border * 2L > Integer.MAX_VALUE / scale) throw new IllegalArgumentException("Scale or border too large"); BufferedImage result = new BufferedImage((size + border * 2) * scale, (size + border * 2) * scale, BufferedImage.TYPE_INT_RGB); for (int y = 0; y < result.getHeight(); y++) { for (int x = 0; x < result.getWidth(); x++) { boolean color = getModule(x / scale - border, y / scale - border); result.setRGB(x, y, color ? 0x000000 : 0xFFFFFF); } } return result; } /** * Returns a string of SVG code for an image depicting this QR Code, with the specified number * of border modules. The string always uses Unix newlines (\n), regardless of the platform. * @param border the number of border modules to add, which must be non-negative * @return a string representing this QR Code as an SVG XML document * @throws IllegalArgumentException if the border is negative */ public String toSvgString(int border) { if (border < 0) throw new IllegalArgumentException("Border must be non-negative"); long brd = border; StringBuilder sb = new StringBuilder() .append("\n") .append("\n") .append(String.format("\n") .toString(); } /*---- Private helper methods for constructor: Drawing function modules ----*/ // Draws two copies of the format bits (with its own error correction code) // based on the given mask and this object's error correction level field. private void drawFormatBits(int msk) { // Calculate error correction code and pack bits int data = errorCorrectionLevel.formatBits << 3 | msk; // errCorrLvl is uint2, mask is uint3 int rem = data; for (int i = 0; i < 10; i++) rem = (rem << 1) ^ ((rem >>> 9) * 0x537); int bits = (data << 10 | rem) ^ 0x5412; // uint15 assert bits >>> 15 == 0; // Draw first copy for (int i = 0; i <= 5; i++) setModule(8, i, getBit(bits, i)); setModule(8, 7, getBit(bits, 6)); setModule(8, 8, getBit(bits, 7)); setModule(7, 8, getBit(bits, 8)); for (int i = 9; i < 15; i++) setModule(14 - i, 8, getBit(bits, i)); // Draw second copy for (int i = 0; i < 8; i++) setModule(size - 1 - i, 8, getBit(bits, i)); for (int i = 8; i < 15; i++) setModule(8, size - 15 + i, getBit(bits, i)); setModule(8, size - 8, 1); // Always dark } // Sets the module at the given coordinates to the given color. // Only used by the constructor. Coordinates must be in bounds. private void setModule(int x, int y, int dark) { assert 0 <= x && x < size; assert 0 <= y && y < size; assert dark == 0 || dark == 1; int i = y * size + x; modules[i >>> 5] &= ~(1 << i); modules[i >>> 5] |= dark << i; } /*---- Private helper methods for constructor: Codewords and masking ----*/ // Returns a new byte string representing the given data with the appropriate error correction // codewords appended to it, based on this object's version and error correction level. private byte[] addEccAndInterleave(byte[] data) { Objects.requireNonNull(data); if (data.length != getNumDataCodewords(version, errorCorrectionLevel)) throw new IllegalArgumentException(); // Calculate parameter numbers int numBlocks = NUM_ERROR_CORRECTION_BLOCKS[errorCorrectionLevel.ordinal()][version]; int blockEccLen = ECC_CODEWORDS_PER_BLOCK [errorCorrectionLevel.ordinal()][version]; int rawCodewords = QrTemplate.getNumRawDataModules(version) / 8; int numShortBlocks = numBlocks - rawCodewords % numBlocks; int shortBlockDataLen = rawCodewords / numBlocks - blockEccLen; // Split data into blocks, calculate ECC, and interleave // (not concatenate) the bytes into a single sequence byte[] result = new byte[rawCodewords]; ReedSolomonGenerator rs = ReedSolomonGenerator.MEMOIZER.get(blockEccLen); byte[] ecc = new byte[blockEccLen]; // Temporary storage per iteration for (int i = 0, k = 0; i < numBlocks; i++) { int datLen = shortBlockDataLen + (i < numShortBlocks ? 0 : 1); rs.getRemainder(data, k, datLen, ecc); for (int j = 0, l = i; j < datLen; j++, k++, l += numBlocks) { // Copy data if (j == shortBlockDataLen) l -= numShortBlocks; result[l] = data[k]; } for (int j = 0, l = data.length + i; j < blockEccLen; j++, l += numBlocks) // Copy ECC result[l] = ecc[j]; } return result; } // Draws the given sequence of 8-bit codewords (data and error correction) // onto the entire data area of this QR Code, based on the given bit indexes. private void drawCodewords(int[] dataOutputBitIndexes, byte[] allCodewords) { Objects.requireNonNull(dataOutputBitIndexes); Objects.requireNonNull(allCodewords); if (allCodewords.length * 8 != dataOutputBitIndexes.length) throw new IllegalArgumentException(); for (int i = 0; i < dataOutputBitIndexes.length; i++) { int j = dataOutputBitIndexes[i]; int bit = getBit(allCodewords[i >>> 3], ~i & 7); modules[j >>> 5] |= bit << j; } } // XORs the codeword modules in this QR Code with the given mask pattern. // The function modules must be marked and the codeword bits must be drawn // before masking. Due to the arithmetic of XOR, calling applyMask() with // the same mask value a second time will undo the mask. A final well-formed // QR Code needs exactly one (not zero, two, etc.) mask applied. private void applyMask(int[] msk) { if (msk.length != modules.length) throw new IllegalArgumentException(); for (int i = 0; i < msk.length; i++) modules[i] ^= msk[i]; } // A messy helper function for the constructor. This QR Code must be in an unmasked state when this // method is called. The 'mask' argument is the requested mask, which is -1 for auto or 0 to 7 for fixed. // This method applies and returns the actual mask chosen, from 0 to 7. private int handleConstructorMasking(int[][] masks, int msk) { if (msk == -1) { // Automatically choose best mask int minPenalty = Integer.MAX_VALUE; for (int i = 0; i < 8; i++) { applyMask(masks[i]); drawFormatBits(i); int penalty = getPenaltyScore(); if (penalty < minPenalty) { msk = i; minPenalty = penalty; } applyMask(masks[i]); // Undoes the mask due to XOR } } assert 0 <= msk && msk <= 7; applyMask(masks[msk]); // Apply the final choice of mask drawFormatBits(msk); // Overwrite old format bits return msk; // The caller shall assign this value to the final-declared field } // Calculates and returns the penalty score based on state of this QR Code's current modules. // This is used by the automatic mask choice algorithm to find the mask pattern that yields the lowest score. private int getPenaltyScore() { int result = 0; int dark = 0; int[] runHistory = new int[7]; // Iterate over adjacent pairs of rows for (int index = 0, downIndex = size, end = size * size; index < end; ) { int runColor = 0; int runX = 0; Arrays.fill(runHistory, 0); int curRow = 0; int nextRow = 0; for (int x = 0; x < size; x++, index++, downIndex++) { int c = getBit(modules[index >>> 5], index); if (c == runColor) { runX++; if (runX == 5) result += PENALTY_N1; else if (runX > 5) result++; } else { finderPenaltyAddHistory(runX, runHistory); if (runColor == 0) result += finderPenaltyCountPatterns(runHistory) * PENALTY_N3; runColor = c; runX = 1; } dark += c; if (downIndex < end) { curRow = ((curRow << 1) | c) & 3; nextRow = ((nextRow << 1) | getBit(modules[downIndex >>> 5], downIndex)) & 3; // 2*2 blocks of modules having same color if (x >= 1 && (curRow == 0 || curRow == 3) && curRow == nextRow) result += PENALTY_N2; } } result += finderPenaltyTerminateAndCount(runColor, runX, runHistory) * PENALTY_N3; } // Iterate over single columns for (int x = 0; x < size; x++) { int runColor = 0; int runY = 0; Arrays.fill(runHistory, 0); for (int y = 0, index = x; y < size; y++, index += size) { int c = getBit(modules[index >>> 5], index); if (c == runColor) { runY++; if (runY == 5) result += PENALTY_N1; else if (runY > 5) result++; } else { finderPenaltyAddHistory(runY, runHistory); if (runColor == 0) result += finderPenaltyCountPatterns(runHistory) * PENALTY_N3; runColor = c; runY = 1; } } result += finderPenaltyTerminateAndCount(runColor, runY, runHistory) * PENALTY_N3; } // Balance of dark and light modules int total = size * size; // Note that size is odd, so dark/total != 1/2 // Compute the smallest integer k >= 0 such that (45-5k)% <= dark/total <= (55+5k)% int k = (Math.abs(dark * 20 - total * 10) + total - 1) / total - 1; result += k * PENALTY_N4; return result; } /*---- Private helper functions ----*/ // Returns the number of 8-bit data (i.e. not error correction) codewords contained in any // QR Code of the given version number and error correction level, with remainder bits discarded. // This stateless pure function could be implemented as a (40*4)-cell lookup table. static int getNumDataCodewords(int ver, Ecc ecl) { return QrTemplate.getNumRawDataModules(ver) / 8 - ECC_CODEWORDS_PER_BLOCK [ecl.ordinal()][ver] * NUM_ERROR_CORRECTION_BLOCKS[ecl.ordinal()][ver]; } // Can only be called immediately after a light run is added, and // returns either 0, 1, or 2. A helper function for getPenaltyScore(). private int finderPenaltyCountPatterns(int[] runHistory) { int n = runHistory[1]; assert n <= size * 3; boolean core = n > 0 && runHistory[2] == n && runHistory[3] == n * 3 && runHistory[4] == n && runHistory[5] == n; return (core && runHistory[0] >= n * 4 && runHistory[6] >= n ? 1 : 0) + (core && runHistory[6] >= n * 4 && runHistory[0] >= n ? 1 : 0); } // Must be called at the end of a line (row or column) of modules. A helper function for getPenaltyScore(). private int finderPenaltyTerminateAndCount(int currentRunColor, int currentRunLength, int[] runHistory) { if (currentRunColor == 1) { // Terminate dark run finderPenaltyAddHistory(currentRunLength, runHistory); currentRunLength = 0; } currentRunLength += size; // Add light border to final run finderPenaltyAddHistory(currentRunLength, runHistory); return finderPenaltyCountPatterns(runHistory); } // Pushes the given value to the front and drops the last value. A helper function for getPenaltyScore(). private void finderPenaltyAddHistory(int currentRunLength, int[] runHistory) { if (runHistory[0] == 0) currentRunLength += size; // Add light border to initial run System.arraycopy(runHistory, 0, runHistory, 1, runHistory.length - 1); runHistory[0] = currentRunLength; } // Returns 0 or 1 based on the (i mod 32)'th bit of x. static int getBit(int x, int i) { return (x >>> i) & 1; } /*---- Constants and tables ----*/ /** The minimum version number (1) supported in the QR Code Model 2 standard. */ public static final int MIN_VERSION = 1; /** The maximum version number (40) supported in the QR Code Model 2 standard. */ public static final int MAX_VERSION = 40; // For use in getPenaltyScore(), when evaluating which mask is best. private static final int PENALTY_N1 = 3; private static final int PENALTY_N2 = 3; private static final int PENALTY_N3 = 40; private static final int PENALTY_N4 = 10; private static final byte[][] ECC_CODEWORDS_PER_BLOCK = { // Version: (note that index 0 is for padding, and is set to an illegal value) //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 {-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 {-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 {-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 {-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 }; private static final byte[][] NUM_ERROR_CORRECTION_BLOCKS = { // Version: (note that index 0 is for padding, and is set to an illegal value) //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 {-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 {-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 {-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 {-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 }; /*---- Public helper enumeration ----*/ /** * The error correction level in a QR Code symbol. */ public enum Ecc { // Must be declared in ascending order of error protection // so that the implicit ordinal() and values() work properly /** The QR Code can tolerate about 7% erroneous codewords. */ LOW(1), /** The QR Code can tolerate about 15% erroneous codewords. */ MEDIUM(0), /** The QR Code can tolerate about 25% erroneous codewords. */ QUARTILE(3), /** The QR Code can tolerate about 30% erroneous codewords. */ HIGH(2); // In the range 0 to 3 (unsigned 2-bit integer). final int formatBits; // Constructor. private Ecc(int fb) { formatBits = fb; } } }