private static Version ChooseVersion(int numInputBits, ErrorCorrectionLevel ecLevel)
{
for (int versionNum = 1; versionNum <= 40; versionNum++)
{
var version = Version.GetVersionForNumber(versionNum);
if (WillFit(numInputBits, version, ecLevel))
{
return version;
}
}
throw new WriterException("Data too big");
}
/// <summary>
/// Decides the smallest version of QR code that will contain all of the provided data.
/// </summary>
/// <exception cref="WriterException">if the data cannot fit in any version</exception>
private static Version RecommendVersion(ErrorCorrectionLevel ecLevel, Mode mode, BitArray headerBits, BitArray dataBits)
{
// Hard part: need to know version to know how many bits length takes. But need to know how many
// bits it takes to know version. First we take a guess at version by assuming version will be
// the minimum, 1:
var provisionalBitsNeeded = CalculateBitsNeeded(mode, headerBits, dataBits, Version.GetVersionForNumber(1));
var provisionalVersion = ChooseVersion(provisionalBitsNeeded, ecLevel);
// Use that guess to calculate the right version. I am still not sure this works in 100% of cases.
var bitsNeeded = CalculateBitsNeeded(mode, headerBits, dataBits, provisionalVersion);
return ChooseVersion(bitsNeeded, ecLevel);
}
/// <summary></summary>
/// <returns>true if the number of input bits will fit in a code with the specified version and error correction level.</returns>
private static bool WillFit(int numInputBits, Version version, ErrorCorrectionLevel ecLevel)
{
// In the following comments, we use numbers of Version 7-H.
// numBytes = 196
var numBytes = version.TotalCodewords;
// getNumECBytes = 130
var ecBlocks = version.GetECBlocksForLevel(ecLevel);
var numEcBytes = ecBlocks.TotalECCodewords;
// getNumDataBytes = 196 - 130 = 66
var numDataBytes = numBytes - numEcBytes;
var totalInputBytes = (numInputBits + 7) / 8;
return numDataBytes >= totalInputBytes;
}
static int ChooseMaskPattern(BitArray bits, ErrorCorrectionLevel ecLevel, Version version, ByteMatrix matrix)
{
int minPenalty = Int32.MaxValue; // Lower penalty is better.
int bestMaskPattern = -1;
// We try all mask patterns to choose the best one.
for (int maskPattern = 0; maskPattern < QRCode.NUM_MASK_PATTERNS; maskPattern++)
{
MatrixUtil.BuildMatrix(bits, ecLevel, version, maskPattern, matrix);
int penalty = CalculateMaskPenalty(matrix);
if (penalty < minPenalty)
{
minPenalty = penalty;
bestMaskPattern = maskPattern;
}
}
return bestMaskPattern;
}
internal static DecoderResult Decode(byte[] bytes,
Version version,
ErrorCorrectionLevel ecLevel)
{
var bits = new BitSource(bytes);
var result = new StringBuilder(50);
var byteSegments = new List <byte[]>(1);
var symbolSequence = -1;
var parityData = -1;
try
{
CharacterSetECI currentCharacterSetECI = null;
bool fc1InEffect = false;
Mode mode;
do
{
// While still another segment to read...
if (bits.Available() < 4)
{
// OK, assume we're done. Really, a TERMINATOR mode should have been recorded here
mode = Mode.TERMINATOR;
}
else
{
try
{
mode = Mode.ForBits(bits.ReadBits(4)); // mode is encoded by 4 bits
}
catch (ArgumentException)
{
return(null);
}
}
switch (mode.Name)
{
case Mode.Names.TERMINATOR:
break;
case Mode.Names.FNC1_FIRST_POSITION:
case Mode.Names.FNC1_SECOND_POSITION:
// We do little with FNC1 except alter the parsed result a bit according to the spec
fc1InEffect = true;
break;
case Mode.Names.STRUCTURED_APPEND:
if (bits.Available() < 16)
{
return(null);
}
// not really supported; but sequence number and parity is added later to the result metadata
// Read next 8 bits (symbol sequence #) and 8 bits (parity data), then continue
symbolSequence = bits.ReadBits(8);
parityData = bits.ReadBits(8);
break;
case Mode.Names.ECI:
// Count doesn't apply to ECI
int value = ParseECIValue(bits);
currentCharacterSetECI = CharacterSetECI.GetCharacterSetECIByValue(value);
if (currentCharacterSetECI == null)
{
return(null);
}
break;
case Mode.Names.HANZI:
// First handle Hanzi mode which does not start with character count
//chinese mode contains a sub set indicator right after mode indicator
int subset = bits.ReadBits(4);
int countHanzi = bits.ReadBits(mode.GetCharacterCountBits(version));
if (subset == GB2312_SUBSET)
{
if (!DecodeHanziSegment(bits, result, countHanzi))
{
return(null);
}
}
break;
default:
// "Normal" QR code modes:
// How many characters will follow, encoded in this mode?
int count = bits.ReadBits(mode.GetCharacterCountBits(version));
switch (mode.Name)
{
case Mode.Names.NUMERIC:
if (!DecodeNumericSegment(bits, result, count))
{
return(null);
}
break;
case Mode.Names.ALPHANUMERIC:
if (!DecodeAlphanumericSegment(bits, result, count, fc1InEffect))
{
return(null);
}
break;
case Mode.Names.BYTE:
if (!DecodeByteSegment(bits, result, count, currentCharacterSetECI, byteSegments))
{
return(null);
}
break;
case Mode.Names.KANJI:
if (!DecodeKanjiSegment(bits, result, count))
{
return(null);
}
break;
default:
return(null);
}
break;
}
} while (mode != Mode.TERMINATOR);
}
catch (ArgumentException)
{
// from readBits() calls
return(null);
}
var resultString = result.ToString().Replace("\r\n", "\n").Replace("\n", Environment.NewLine);
return(new DecoderResult(bytes, resultString));
}
/// <summary>
/// Gets the EC blocks for level.
/// </summary>
/// <param name="ecLevel">The ec level.</param>
/// <returns></returns>
public ECBlocks GetECBlocksForLevel(ErrorCorrectionLevel ecLevel)
{
return(ecBlocks[ecLevel.Ordinal]);
}
/// <summary>
/// Encodes the specified content.
/// </summary>
/// <param name="content">The content.</param>
/// <param name="ecLevel">The ec level.</param>
/// <param name="hints">The hints.</param>
/// <returns></returns>
public static QRCode Encode(String content, ErrorCorrectionLevel ecLevel)
{
var encoding = DEFAULT_BYTE_MODE_ENCODING;
var generateECI = !DEFAULT_BYTE_MODE_ENCODING.Equals(encoding);
// Pick an encoding mode appropriate for the content. Note that this will not attempt to use
// multiple modes / segments even if that were more efficient. Twould be nice.
var mode = ChooseMode(content, encoding);
// This will store the header information, like mode and
// length, as well as "header" segments like an ECI segment.
var headerBits = new BitArray();
// Append ECI segment if applicable
if (mode == Mode.BYTE && generateECI)
{
var eci = CharacterSetECI.GetCharacterSetECIByName(encoding);
if (eci != null)
{
AppendECI(eci, headerBits);
}
}
// (With ECI in place,) Write the mode marker
AppendModeInfo(mode, headerBits);
// Collect data within the main segment, separately, to count its size if needed. Don't add it to
// main payload yet.
var dataBits = new BitArray();
AppendBytes(content, mode, dataBits, encoding);
Version version = RecommendVersion(ecLevel, mode, headerBits, dataBits);
var headerAndDataBits = new BitArray();
headerAndDataBits.AppendBitArray(headerBits);
// Find "length" of main segment and write it
var numLetters = mode == Mode.BYTE ? dataBits.SizeInBytes : content.Length;
AppendLengthInfo(numLetters, version, mode, headerAndDataBits);
// Put data together into the overall payload
headerAndDataBits.AppendBitArray(dataBits);
var ecBlocks = version.GetECBlocksForLevel(ecLevel);
var numDataBytes = version.TotalCodewords - ecBlocks.TotalECCodewords;
// Terminate the bits properly.
TerminateBits(numDataBytes, headerAndDataBits);
// Interleave data bits with error correction code.
var finalBits = InterleaveWithECBytes(headerAndDataBits,
version.TotalCodewords,
numDataBytes,
ecBlocks.NumBlocks);
var qrCode = new QRCode
{
ECLevel = ecLevel,
Mode = mode,
Version = version
};
// Choose the mask pattern and set to "qrCode".
var dimension = version.DimensionForVersion;
var matrix = new ByteMatrix(dimension, dimension);
var maskPattern = ChooseMaskPattern(finalBits, ecLevel, version, matrix);
qrCode.MaskPattern = maskPattern;
// Build the matrix and set it to "qrCode".
MatrixUtil.BuildMatrix(finalBits, ecLevel, version, maskPattern, matrix);
qrCode.Matrix = matrix;
return qrCode;
}
