internal static Version decodeVersionInformation(int versionBits)
{
int bestDifference = Int32.MaxValue;
int bestVersion = 0;
for (int i = 0; i < VERSION_DECODE_INFO.Length; i++)
{
int targetVersion = VERSION_DECODE_INFO[i];
// Do the version info bits match exactly? done.
if (targetVersion == versionBits)
{
return(getVersionForNumber(i + 7));
}
// Otherwise see if this is the closest to a real version info bit string
// we have seen so far
int bitsDifference = FormatInformation.numBitsDiffering(versionBits, targetVersion);
if (bitsDifference < bestDifference)
{
bestVersion = i + 7;
bestDifference = bitsDifference;
}
}
// We can tolerate up to 3 bits of error since no two version info codewords will
// differ in less than 8 bits.
if (bestDifference <= 3)
{
return(getVersionForNumber(bestVersion));
}
// If we didn't find a close enough match, fail
return(null);
}
/// <summary>
/// Decodes the format information.
/// </summary>
/// <param name="maskedFormatInfo1">format info indicator, with mask still applied</param>
/// <param name="maskedFormatInfo2">The masked format info2.</param>
/// <returns>
/// information about the format it specifies, or <code>null</code>
/// if doesn't seem to match any known pattern
/// </returns>
internal static FormatInformation decodeFormatInformation(int maskedFormatInfo1, int maskedFormatInfo2)
{
FormatInformation formatInfo = doDecodeFormatInformation(maskedFormatInfo1, maskedFormatInfo2);
if (formatInfo != null)
{
return(formatInfo);
}
// Should return null, but, some QR codes apparently
// do not mask this info. Try again by actually masking the pattern
// first
return(doDecodeFormatInformation(maskedFormatInfo1 ^ FORMAT_INFO_MASK_QR,
maskedFormatInfo2 ^ FORMAT_INFO_MASK_QR));
}
/// <summary> <p>Reads format information from one of its two locations within the QR Code.</p>
///
/// </summary>
/// <returns> {@link FormatInformation} encapsulating the QR Code's format info
/// </returns>
/// <throws> ReaderException if both format information locations cannot be parsed as </throws>
/// <summary> the valid encoding of format information
/// </summary>
internal FormatInformation readFormatInformation()
{
if (parsedFormatInfo != null)
{
return(parsedFormatInfo);
}
// Read top-left format info bits
int formatInfoBits1 = 0;
for (int i = 0; i < 6; i++)
{
formatInfoBits1 = copyBit(i, 8, formatInfoBits1);
}
// .. and skip a bit in the timing pattern ...
formatInfoBits1 = copyBit(7, 8, formatInfoBits1);
formatInfoBits1 = copyBit(8, 8, formatInfoBits1);
formatInfoBits1 = copyBit(8, 7, formatInfoBits1);
// .. and skip a bit in the timing pattern ...
for (int j = 5; j >= 0; j--)
{
formatInfoBits1 = copyBit(8, j, formatInfoBits1);
}
// Read the top-right/bottom-left pattern too
int dimension = bitMatrix.Height;
int formatInfoBits2 = 0;
int jMin = dimension - 7;
for (int j = dimension - 1; j >= jMin; j--)
{
formatInfoBits2 = copyBit(8, j, formatInfoBits2);
}
for (int i = dimension - 8; i < dimension; i++)
{
formatInfoBits2 = copyBit(i, 8, formatInfoBits2);
}
parsedFormatInfo = FormatInformation.decodeFormatInformation(formatInfoBits1, formatInfoBits2);
if (parsedFormatInfo != null)
{
return(parsedFormatInfo);
}
return(null);
}
/// <summary> <p>Reads the bits in the {@link BitMatrix} representing the finder pattern in the
/// correct order in order to reconstitute the codewords bytes contained within the
/// QR Code.</p>
///
/// </summary>
/// <returns> bytes encoded within the QR Code
/// </returns>
/// <throws> ReaderException if the exact number of bytes expected is not read </throws>
internal byte[] readCodewords()
{
FormatInformation formatInfo = readFormatInformation();
if (formatInfo == null)
{
return(null);
}
Version version = readVersion();
if (version == null)
{
return(null);
}
// Get the data mask for the format used in this QR Code. This will exclude
// some bits from reading as we wind through the bit matrix.
DataMask dataMask = DataMask.forReference(formatInfo.DataMask);
int dimension = bitMatrix.Height;
dataMask.unmaskBitMatrix(bitMatrix, dimension);
BitMatrix functionPattern = version.buildFunctionPattern();
bool readingUp = true;
byte[] result = new byte[version.TotalCodewords];
int resultOffset = 0;
int currentByte = 0;
int bitsRead = 0;
// Read columns in pairs, from right to left
for (int j = dimension - 1; j > 0; j -= 2)
{
if (j == 6)
{
// Skip whole column with vertical alignment pattern;
// saves time and makes the other code proceed more cleanly
j--;
}
// Read alternatingly from bottom to top then top to bottom
for (int count = 0; count < dimension; count++)
{
int i = readingUp ? dimension - 1 - count : count;
for (int col = 0; col < 2; col++)
{
// Ignore bits covered by the function pattern
if (!functionPattern[j - col, i])
{
// Read a bit
bitsRead++;
currentByte <<= 1;
if (bitMatrix[j - col, i])
{
currentByte |= 1;
}
// If we've made a whole byte, save it off
if (bitsRead == 8)
{
result[resultOffset++] = (byte)currentByte;
bitsRead = 0;
currentByte = 0;
}
}
}
}
readingUp ^= true; // readingUp = !readingUp; // switch directions
}
if (resultOffset != version.TotalCodewords)
{
return(null);
}
return(result);
}