private DecoderResult decode(BitMatrixParser parser, Map<DecodeHintType, ?> hints)
throws FormatException, ChecksumException {
Version version = parser.readVersion();
ErrorCorrectionLevel ecLevel = parser.readFormatInformation().getErrorCorrectionLevel();
// Read codewords
byte[] codewords = parser.readCodewords();
// Separate into data blocks
DataBlock[] dataBlocks = DataBlock.getDataBlocks(codewords, version, ecLevel);
// Count total number of data bytes
int totalBytes = 0;
for (DataBlock dataBlock : dataBlocks) {
totalBytes += dataBlock.getNumDataCodewords();
}
byte[] resultBytes = new byte[totalBytes];
int resultOffset = 0;
// Error-correct and copy data blocks together into a stream of bytes
for (DataBlock dataBlock : dataBlocks) {
byte[] codewordBytes = dataBlock.getCodewords();
int numDataCodewords = dataBlock.getNumDataCodewords();
correctErrors(codewordBytes, numDataCodewords);
for (int i = 0; i < numDataCodewords; i++) {
resultBytes[resultOffset++] = codewordBytes[i];
}
}
// Decode the contents of that stream of bytes
return DecodedBitStreamParser.decode(resultBytes, version, ecLevel, hints);
}
/**
* Decodes a QR Code represented as a {@link BitMatrix}. A 1 or "true" is taken to mean a black
* module.
*
* @param bits booleans representing white/black QR Code modules
* @param hints decoding hints that should be used to influence decoding
* @return text and bytes encoded within the QR Code
* @throws FormatException if the QR Code cannot be decoded
* @throws ChecksumException if error correction fails
*/
public DecoderResult decode(BitMatrix bits, Map<DecodeHintType, ?> hints)
throws FormatException, ChecksumException {
// Construct a parser and read version, error-correction level
BitMatrixParser parser = new BitMatrixParser(bits);
FormatException fe = null;
ChecksumException ce = null;
try {
return decode(parser, hints);
} catch (FormatException e) {
fe = e;
} catch (ChecksumException e) {
ce = e;
}
try {
// Revert the bit matrix
parser.remask();
// Will be attempting a mirrored reading of the version and format info.
parser.setMirror(true);
// Preemptively read the version.
parser.readVersion();
// Preemptively read the format information.
parser.readFormatInformation();
/*
* Since we're here, this means we have successfully detected some kind
* of version and format information when mirrored. This is a good sign,
* that the QR code may be mirrored, and we should try once more with a
* mirrored content.
*/
// Prepare for a mirrored reading.
parser.mirror();
DecoderResult result = decode(parser, hints);
// Success! Notify the caller that the code was mirrored.
result.setOther(new QRCodeDecoderMetaData(true));
return result;
} catch (FormatException | ChecksumException e) {
// Throw the exception from the original reading
if (fe != null) {
throw fe;
}
if (ce != null) {
throw ce;
}
throw e;
}
}