Support QR Code Model1 (zxing-cpp#633)

This adds basic support to read/decode QR Code Model 1 symbols. It can be considered to fix zxing-cpp#614, although axxel believes that it only works for version 1-4. For higher versions there is still work to be done regarding the ecBlock interlacing (or the lack thereof).

---------

Co-authored-by: axxel <[email protected]>

Author: sayzzy-nt

core/src/qrcode/QRBitMatrixParser.cpp

@@ -135,6 +135,66 @@ static ByteArray ReadQRCodewords(const BitMatrix& bitMatrix, const Version& vers
 	return result;
 }
 
+static ByteArray ReadQRCodewordsModel1(const BitMatrix& bitMatrix, const Version& version, const FormatInformation& formatInfo)
+{
+
+	ByteArray result;
+	result.reserve(version.totalCodewords());
+	int dimension = bitMatrix.height();
+	int columns = dimension / 4 + 1 + 2;
+	for (int j = 0; j < columns; j++) {
+		if (j <= 1) { // vertical symbols on the right side
+			int rows = (dimension - 8) / 4;
+			for (int i = 0; i < rows; i++) {
+				if (j == 0 && i % 2 == 0 && i > 0 && i < rows - 1) // extension
+					continue;
+				int x = (dimension - 1) - (j * 2);
+				int y = (dimension - 1) - (i * 4);
+				uint8_t currentByte = 0;
+				for (int b = 0; b < 8; b++) {
+					AppendBit(currentByte, GetDataMaskBit(formatInfo.dataMask, x - b % 2, y - (b / 2))
+											   != getBit(bitMatrix, x - b % 2, y - (b / 2), formatInfo.isMirrored));
+				}
+				result.push_back(currentByte);
+			}
+		} else if (columns - j <= 4) { // vertical symbols on the left side
+			int rows = (dimension - 16) / 4;
+			for (int i = 0; i < rows; i++) {
+				int x = (columns - j - 1) * 2 + 1 + (columns - j == 4 ? 1 : 0); // timing
+				int y = (dimension - 1) - 8 - (i * 4);
+				uint8_t currentByte = 0;
+				for (int b = 0; b < 8; b++) {
+					AppendBit(currentByte, GetDataMaskBit(formatInfo.dataMask, x - b % 2, y - (b / 2))
+											   != getBit(bitMatrix, x - b % 2, y - (b / 2), formatInfo.isMirrored));
+				}
+				result.push_back(currentByte);
+			}
+		} else { // horizontal symbols
+			int rows = dimension / 2;
+			for (int i = 0; i < rows; i++) {
+				if (j == 2 && i >= rows - 4) // alignment & finder
+					continue;
+				if (i == 0 && j % 2 == 1 && j + 1 != columns - 4) // extension
+					continue;
+				int x = (dimension - 1) - (2 * 2) - (j - 2) * 4;
+				int y = (dimension - 1) - (i * 2) - (i >= rows - 3 ? 1 : 0); // timing
+				uint8_t currentByte = 0;
+				for (int b = 0; b < 8; b++) {
+					AppendBit(currentByte, GetDataMaskBit(formatInfo.dataMask, x - b % 4, y - (b / 4))
+											   != getBit(bitMatrix, x - b % 4, y - (b / 4), formatInfo.isMirrored));
+				}
+				result.push_back(currentByte);
+			}
+		}
+	}
+
+	result[0] &= 0xf; // ignore corner
+	if (Size(result) != version.totalCodewords())
+		return {};
+
+	return result;
+}
+
 static ByteArray ReadMQRCodewords(const BitMatrix& bitMatrix, const QRCode::Version& version, const FormatInformation& formatInfo)
 {
 	BitMatrix functionPattern = version.buildFunctionPattern();
@@ -185,9 +245,12 @@ ByteArray ReadCodewords(const BitMatrix& bitMatrix, const Version& version, cons
 {
 	if (!hasValidDimension(bitMatrix, version.isMicroQRCode()))
 		return {};
-
-	return version.isMicroQRCode() ? ReadMQRCodewords(bitMatrix, version, formatInfo)
-								   : ReadQRCodewords(bitMatrix, version, formatInfo);
+	if (version.isMicroQRCode())
+		return ReadMQRCodewords(bitMatrix, version, formatInfo);
+	else if (formatInfo.isModel1)
+		return ReadQRCodewordsModel1(bitMatrix, version, formatInfo);
+	else
+		return ReadQRCodewords(bitMatrix, version, formatInfo);
 }
 
 } // namespace ZXing::QRCode

core/src/qrcode/QRDecoder.cpp

@@ -237,6 +237,9 @@ DecoderResult DecodeBitStream(ByteArray&& bytes, const Version& version, ErrorCo
 	StructuredAppendInfo structuredAppend;
 	const int modeBitLength = CodecModeBitsLength(version);
 
+	if (version.isQRCodeModel1())
+		bits.readBits(4); // Model 1 is leading with 4 0-bits -> drop them
+
 	try
 	{
 		while(!IsEndOfStream(bits, version)) {
@@ -316,14 +319,16 @@ DecoderResult DecodeBitStream(ByteArray&& bytes, const Version& version, ErrorCo
 
 DecoderResult Decode(const BitMatrix& bits)
 {
-	const Version* pversion = ReadVersion(bits);
+	bool isMicroQRCode = bits.height() < 21;
+	auto formatInfo = ReadFormatInformation(bits, isMicroQRCode);
+	if (!formatInfo.isValid())
+		return FormatError("Invalid format information");
+
+	const Version* pversion = formatInfo.isModel1 ? Version::FromDimension(bits.height(), true) : ReadVersion(bits);
 	if (!pversion)
 		return FormatError("Invalid version");
-	const Version& version = *pversion;
 
-	auto formatInfo = ReadFormatInformation(bits, version.isMicroQRCode());
-	if (!formatInfo.isValid())
-		return FormatError("Invalid format information");
+	const Version& version = *pversion;
 
 	// Read codewords
 	ByteArray codewords = ReadCodewords(bits, version, formatInfo);

core/src/qrcode/QRFormatInformation.cpp

@@ -15,6 +15,8 @@ namespace ZXing::QRCode {
 
 static const int FORMAT_INFO_MASK_QR = 0x5412;
 
+static const int FORMAT_INFO_MASK_QR_MODEL1 = 0x2825;
+
 /**
 * See ISO 18004:2006, Annex C, Table C.1
 */
@@ -93,13 +95,12 @@ static uint32_t MirrorBits(uint32_t bits)
 	return BitHacks::Reverse(bits) >> 17;
 }
 
-static FormatInformation FindBestFormatInfo(int mask, const std::array<std::pair<int, int>, 32> lookup,
+static FormatInformation FindBestFormatInfo(const std::vector<uint32_t>& masks, const std::array<std::pair<int, int>, 32> lookup,
 											const std::vector<uint32_t>& bits)
 {
 	FormatInformation fi;
 
-	// Some QR codes apparently do not apply the XOR mask. Try without and with additional masking.
-	for (auto mask : {0, mask})
+	for (auto mask : masks)
 		for (int bitsIndex = 0; bitsIndex < Size(bits); ++bitsIndex)
 			for (const auto& [pattern, index] : lookup) {
 				// Find the int in lookup with fewest bits differing
@@ -122,8 +123,16 @@ FormatInformation FormatInformation::DecodeQR(uint32_t formatInfoBits1, uint32_t
 	// maks out the 'Dark Module' for mirrored and non-mirrored case (see Figure 25 in ISO/IEC 18004:2015)
 	uint32_t mirroredFormatInfoBits2 = MirrorBits(((formatInfoBits2 >> 1) & 0b111111110000000) | (formatInfoBits2 & 0b1111111));
 	formatInfoBits2 = ((formatInfoBits2 >> 1) & 0b111111100000000) | (formatInfoBits2 & 0b11111111);
-	auto fi = FindBestFormatInfo(FORMAT_INFO_MASK_QR, FORMAT_INFO_DECODE_LOOKUP,
+	// Some QR codes apparently do not apply the XOR mask. Try without and with additional masking.
+	auto fi = FindBestFormatInfo({0, FORMAT_INFO_MASK_QR}, FORMAT_INFO_DECODE_LOOKUP,
 								 {formatInfoBits1, formatInfoBits2, MirrorBits(formatInfoBits1), mirroredFormatInfoBits2});
+	auto fi_model1 = FindBestFormatInfo({FORMAT_INFO_MASK_QR ^ FORMAT_INFO_MASK_QR_MODEL1}, FORMAT_INFO_DECODE_LOOKUP,
+										{formatInfoBits1, formatInfoBits2, MirrorBits(formatInfoBits1), mirroredFormatInfoBits2});
+
+	if (fi_model1.hammingDistance < fi.hammingDistance) {
+		fi_model1.isModel1 = true;
+		fi = fi_model1;
+	}
 
 	// Use bits 3/4 for error correction, and 0-2 for mask.
 	fi.ecLevel = ECLevelFromBits((fi.index >> 3) & 0x03);
@@ -139,7 +148,7 @@ FormatInformation FormatInformation::DecodeQR(uint32_t formatInfoBits1, uint32_t
 FormatInformation FormatInformation::DecodeMQR(uint32_t formatInfoBits)
 {
 	// We don't use the additional masking (with 0x4445) to work around potentially non complying MicroQRCode encoders
-	auto fi = FindBestFormatInfo(0, FORMAT_INFO_DECODE_LOOKUP_MICRO, {formatInfoBits, MirrorBits(formatInfoBits)});
+	auto fi = FindBestFormatInfo({0}, FORMAT_INFO_DECODE_LOOKUP_MICRO, {formatInfoBits, MirrorBits(formatInfoBits)});
 
 	constexpr uint8_t BITS_TO_VERSION[] = {1, 2, 2, 3, 3, 4, 4, 4};
 

core/src/qrcode/QRFormatInformation.h

@@ -18,6 +18,7 @@ class FormatInformation
 	uint8_t index = 255;
 	uint8_t hammingDistance = 255;
 	bool isMirrored = false;
+	bool isModel1 = false;
 	uint8_t dataMask = 0;
 	uint8_t microVersion = 0;
 	uint8_t bitsIndex = 255;

core/src/qrcode/QRVersion.cpp

@@ -292,35 +292,136 @@ const Version* Version::AllMicroVersions()
 	return allVersions;
 }
 
+const Version* Version::AllModel1Versions()
+{
+	/**
+	 * See ISO 18004:2000 M.4.2 Table M.2
+	 * See ISO 18004:2000 M.5 Table M.4
+	 */
+	static const Version allVersions[] = {
+		{1, {
+			7 , 1, 19, 0, 0,
+			10, 1, 16, 0, 0,
+			13, 1, 13, 0, 0,
+			17, 1, 9 , 0, 0
+		}},
+		{2, {
+			10, 1, 36, 0, 0,
+			16, 1, 30, 0, 0,
+			22, 1, 24, 0, 0,
+			30, 1, 16, 0, 0,
+		 }},
+		{3, {
+			15, 1, 57, 0, 0,
+			28, 1, 44, 0, 0,
+			36, 1, 36, 0, 0,
+			48, 1, 24, 0, 0,
+		 }},
+		{4, {
+			20, 1, 80, 0, 0,
+			40, 1, 60, 0, 0,
+			50, 1, 50, 0, 0,
+			66, 1, 34, 0, 0,
+		 }},
+		{5, {
+			26, 1, 108, 0, 0,
+			52, 1, 82 , 0, 0,
+			66, 1, 68 , 0, 0,
+			88, 2, 46 , 0, 0,
+			}},
+		{6, {
+			34 , 1, 136, 0, 0,
+			63 , 2, 106, 0, 0,
+			84 , 2, 86 , 0, 0,
+			112, 2, 58 , 0, 0,
+			}},
+		{7, {
+			42 , 1, 170, 0, 0,
+			80 , 2, 132, 0, 0,
+			104, 2, 108, 0, 0,
+			138, 3, 72 , 0, 0,
+			}},
+		{8, {
+			48 , 2, 208, 0, 0,
+			96 , 2, 160, 0, 0,
+			128, 2, 128, 0, 0,
+			168, 3, 87 , 0, 0,
+			}},
+		{9, {
+			60 , 2, 246, 0, 0,
+			120, 2, 186, 0, 0,
+			150, 3, 156, 0, 0,
+			204, 3, 102, 0, 0,
+			}},
+		{10, {
+			68 , 2, 290, 0, 0,
+			136, 2, 222, 0, 0,
+			174, 3, 183, 0, 0,
+			232, 4, 124, 0, 0,
+			}},
+		{11, {
+			80 , 2, 336, 0, 0,
+			160, 4, 256, 0, 0,
+			208, 4, 208, 0, 0,
+			270, 5, 145, 0, 0,
+			}},
+		{12, {
+			92 , 2, 384, 0, 0,
+			184, 4, 292, 0, 0,
+			232, 4, 244, 0, 0,
+			310, 5, 165, 0, 0,
+			}},
+		{13, {
+			108, 3, 432, 0, 0,
+			208, 4, 332, 0, 0,
+			264, 4, 276, 0, 0,
+			348, 6, 192, 0, 0,
+			}},
+		{14, {
+			120, 3, 489, 0, 0,
+			240, 4, 368, 0, 0,
+			300, 5, 310, 0, 0,
+			396, 6, 210, 0, 0,
+			}},
+	};
+	return allVersions;
+}
+
+static inline bool isMicro(const std::array<ECBlocks, 4>& ecBlocks)
+{
+	return ecBlocks[0].codewordsPerBlock < 7 || ecBlocks[0].codewordsPerBlock == 8;
+}
+
 Version::Version(int versionNumber, std::initializer_list<int> alignmentPatternCenters, const std::array<ECBlocks, 4>& ecBlocks)
-	: _versionNumber(versionNumber), _alignmentPatternCenters(alignmentPatternCenters), _ecBlocks(ecBlocks), _isMicro(false)
+	: _versionNumber(versionNumber), _alignmentPatternCenters(alignmentPatternCenters), _ecBlocks(ecBlocks), _isMicro(false), _isModel1(false)
 {
 	_totalCodewords = ecBlocks[0].totalDataCodewords();
 }
 
 Version::Version(int versionNumber, const std::array<ECBlocks, 4>& ecBlocks)
-	: _versionNumber(versionNumber), _ecBlocks(ecBlocks), _isMicro(true)
+	: _versionNumber(versionNumber), _ecBlocks(ecBlocks), _isMicro(isMicro(ecBlocks)), _isModel1(!isMicro(ecBlocks))
 {
 	_totalCodewords = ecBlocks[0].totalDataCodewords();
 }
 
-const Version* Version::FromNumber(int versionNumber, bool isMicro)
+const Version* Version::FromNumber(int versionNumber, bool isMicro, bool isModel1)
 {
-	if (versionNumber < 1 || versionNumber > (isMicro ? 4 : 40)) {
+	if (versionNumber < 1 || versionNumber > (isMicro ? 4 : (isModel1 ? 14 : 40))) {
 		//throw std::invalid_argument("Version should be in range [1-40].");
 		return nullptr;
 	}
-	return &(isMicro ? AllMicroVersions() : AllVersions())[versionNumber - 1];
+
+    return &(isMicro ? AllMicroVersions() : (isModel1 ? AllModel1Versions() : AllVersions()))[versionNumber - 1];
 }
 
-const Version* Version::FromDimension(int dimension)
+const Version* Version::FromDimension(int dimension, bool isModel1)
 {
 	bool isMicro = dimension < 21;
 	if (dimension % DimensionStep(isMicro) != 1) {
 		//throw std::invalid_argument("Unexpected dimension");
 		return nullptr;
 	}
-	return FromNumber((dimension - DimensionOffset(isMicro)) / DimensionStep(isMicro), isMicro);
+	return FromNumber((dimension - DimensionOffset(isMicro)) / DimensionStep(isMicro), isMicro, isModel1);
 }
 
 const Version* Version::DecodeVersionInformation(int versionBitsA, int versionBitsB)

core/src/qrcode/QRVersion.h

@@ -40,6 +40,7 @@ class Version
 	BitMatrix buildFunctionPattern() const;
 
 	bool isMicroQRCode() const { return _isMicro; }
+	bool isQRCodeModel1() const { return _isModel1; }
 
 	static constexpr int DimensionStep(bool isMicro) { return std::array{4, 2}[isMicro]; }
 	static constexpr int DimensionOffset(bool isMicro) { return std::array{17, 9}[isMicro]; }
@@ -54,9 +55,9 @@ class Version
 	* @param dimension dimension in modules
 	* @return Version for a QR Code of that dimension
 	*/
-	static const Version* FromDimension(int dimension);
+	static const Version* FromDimension(int dimension, bool isModel1 = false);
 
-	static const Version* FromNumber(int versionNumber, bool isMicro = false);
+	static const Version* FromNumber(int versionNumber, bool isMicro = false, bool isModel1 = false);
 
 	static const Version* DecodeVersionInformation(int versionBitsA, int versionBitsB = 0);
 
@@ -66,11 +67,13 @@ class Version
 	std::array<ECBlocks, 4> _ecBlocks;
 	int _totalCodewords;
 	bool _isMicro;
+	bool _isModel1;
 
 	Version(int versionNumber, std::initializer_list<int> alignmentPatternCenters, const std::array<ECBlocks, 4> &ecBlocks);
 	Version(int versionNumber, const std::array<ECBlocks, 4>& ecBlocks);
 	static const Version* AllVersions();
 	static const Version* AllMicroVersions();
+	static const Version* AllModel1Versions();
 };
 
 } // QRCode

test/blackbox/BlackboxTestRunner.cpp

@@ -562,12 +562,12 @@ int runBlackBoxTests(const fs::path& testPathPrefix, const std::set<std::string>
 			{ 16, 16, 270 },
 		});
 
-		runTests("qrcode-2", "QRCode", 49, {
-			{ 45, 47, 0   },
-			{ 45, 47, 90  },
-			{ 45, 47, 180 },
-			{ 45, 47, 270 },
-			{ 21, 1, pure }, // the misread is the 'outer' symbol in 16.png
+		runTests("qrcode-2", "QRCode", 50, {
+			{ 46, 48, 0   },
+			{ 46, 48, 90  },
+			{ 46, 48, 180 },
+			{ 46, 48, 270 },
+			{ 22, 1, pure }, // the misread is the 'outer' symbol in 16.png
 		});
 
 		runTests("qrcode-3", "QRCode", 28, {

test/samples/qrcode-2/qr-model-1.png

@@ -0,0 +1 @@
+QR Code Model 1