/// <summary> Terminate bits as described in 8.4.8 and 8.4.9 of JISX0510:2004 (p.24).</summary> internal static void terminateBits(int numDataBytes, BitVector bits) { int capacity = numDataBytes << 3; if (bits.size() > capacity) { throw new WriterException("data bits cannot fit in the QR Code" + bits.size() + " > " + capacity); } // Append termination bits. See 8.4.8 of JISX0510:2004 (p.24) for details. // TODO: srowen says we can remove this for loop, since the 4 terminator bits are optional if // the last byte has less than 4 bits left. So it amounts to padding the last byte with zeroes // either way. for (int i = 0; i < 4 && bits.size() < capacity; ++i) { bits.appendBit(0); } int numBitsInLastByte = bits.size() % 8; // If the last byte isn't 8-bit aligned, we'll add padding bits. if (numBitsInLastByte > 0) { int numPaddingBits = 8 - numBitsInLastByte; for (int i = 0; i < numPaddingBits; ++i) { bits.appendBit(0); } } // Should be 8-bit aligned here. if (bits.size() % 8 != 0) { throw new WriterException("Number of bits is not a multiple of 8"); } // If we have more space, we'll fill the space with padding patterns defined in 8.4.9 (p.24). int numPaddingBytes = numDataBytes - bits.sizeInBytes(); for (int i = 0; i < numPaddingBytes; ++i) { if (i % 2 == 0) { bits.appendBits(0xec, 8); } else { bits.appendBits(0x11, 8); } } if (bits.size() != capacity) { throw new WriterException("Bits size does not equal capacity"); } }
// Make bit vector of version information. On success, store the result in "bits" and return true. // See 8.10 of JISX0510:2004 (p.45) for details. public static void makeVersionInfoBits(int version, BitVector bits) { bits.appendBits(version, 6); int bchCode = calculateBCHCode(version, VERSION_INFO_POLY); bits.appendBits(bchCode, 12); if (bits.size() != 18) { // Just in case. throw new WriterException("should not happen but we got: " + bits.size()); } }
// Embed type information. On success, modify the matrix. public static void embedTypeInfo(ErrorCorrectionLevel ecLevel, int maskPattern, ByteMatrix matrix) { BitVector typeInfoBits = new BitVector(); makeTypeInfoBits(ecLevel, maskPattern, typeInfoBits); for (int i = 0; i < typeInfoBits.size(); ++i) { // Place bits in LSB to MSB order. LSB (least significant bit) is the last value in // "typeInfoBits". int bit = typeInfoBits.at(typeInfoBits.size() - 1 - i); // Type info bits at the left top corner. See 8.9 of JISX0510:2004 (p.46). int x1 = TYPE_INFO_COORDINATES[i][0]; int y1 = TYPE_INFO_COORDINATES[i][1]; matrix.set_Renamed(x1, y1, bit); if (i < 8) { // Right top corner. int x2 = matrix.Width - i - 1; int y2 = 8; matrix.set_Renamed(x2, y2, bit); } else { // Left bottom corner. int x2 = 8; int y2 = matrix.Height - 7 + (i - 8); matrix.set_Renamed(x2, y2, bit); } } }
// Make bit vector of type information. On success, store the result in "bits" and return true. // Encode error correction level and mask pattern. See 8.9 of // JISX0510:2004 (p.45) for details. public static void makeTypeInfoBits(ErrorCorrectionLevel ecLevel, int maskPattern, BitVector bits) { if (!QRCode.isValidMaskPattern(maskPattern)) { throw new WriterException("Invalid mask pattern"); } int typeInfo = (ecLevel.Bits << 3) | maskPattern; bits.appendBits(typeInfo, 5); int bchCode = calculateBCHCode(typeInfo, TYPE_INFO_POLY); bits.appendBits(bchCode, 10); BitVector maskBits = new BitVector(); maskBits.appendBits(TYPE_INFO_MASK_PATTERN, 15); bits.xor(maskBits); if (bits.size() != 15) { // Just in case. throw new WriterException("should not happen but we got: " + bits.size()); } }
// Embed "dataBits" using "getMaskPattern". On success, modify the matrix and return true. // For debugging purposes, it skips masking process if "getMaskPattern" is -1. // See 8.7 of JISX0510:2004 (p.38) for how to embed data bits. public static void embedDataBits(BitVector dataBits, int maskPattern, ByteMatrix matrix) { int bitIndex = 0; int direction = - 1; // Start from the right bottom cell. int x = matrix.Width - 1; int y = matrix.Height - 1; while (x > 0) { // Skip the vertical timing pattern. if (x == 6) { x -= 1; } while (y >= 0 && y < matrix.Height) { for (int i = 0; i < 2; ++i) { int xx = x - i; // Skip the cell if it's not empty. if (!isEmpty(matrix.get_Renamed(xx, y))) { continue; } int bit; if (bitIndex < dataBits.size()) { bit = dataBits.at(bitIndex); ++bitIndex; } else { // Padding bit. If there is no bit left, we'll fill the left cells with 0, as described // in 8.4.9 of JISX0510:2004 (p. 24). bit = 0; } // Skip masking if mask_pattern is -1. if (maskPattern != - 1) { if (MaskUtil.getDataMaskBit(maskPattern, xx, y)) { bit ^= 0x1; } } matrix.set_Renamed(xx, y, bit); } y += direction; } direction = - direction; // Reverse the direction. y += direction; x -= 2; // Move to the left. } // All bits should be consumed. if (bitIndex != dataBits.size()) { throw new WriterException("Not all bits consumed: " + bitIndex + '/' + dataBits.size()); } }