zxing使用byte数组生成二维码和解析二维码

二维码的生成方法网上一搜一大堆，但基本都是直接以字符串进行生成，存储访问路径或一些简单的信息。然而有时就是有这么特殊的需求，需要使用二维码传输数据，数据量还比较大。数据量太大二维码不好生成和扫描，就想到压缩数据，使用jdk的GZIP压缩，得到一个byte数组。byte数组无法生成二维码，直接new String()转回字符串，看下数据量比压缩前还大，base64编码一下，虽然比压缩前小，但是比编码前大多了。那么是否可以直接使用数组生成二维码呢？

改写的jar：重新编译的可使用byte[]生成二维码的zxing-core-3.4.0
使用方法：java压缩字符串并生成二维码

二维码生成

对zxing的core-3.4.0源码进行追踪、查看，new MultiFormatWriter().encode()选择生成QRCode。

我们要生成QRCode，其它的生成方式就不需要，直接改写为：

public BitMatrix encodeQRCode(byte[] contents, int width, int height, Map<EncodeHintType,?> hints) throws WriterException {QRCodeWriter writer = new QRCodeWriter();return writer.encodeQRCode(contents, width, height, hints);}

追踪进入QRCodeWriter的encode方法。

这里主要是对参数的验证，只需要把encode方法改为我们自定义的encodeQRCode方法：

public BitMatrix encodeQRCode(byte[] contents, int width, int height, Map<EncodeHintType,?> hints) throws WriterException {if (contents == null || contents.length == 0) {throw new IllegalArgumentException("Found empty contents");}if (width < 0 || height < 0) {throw new IllegalArgumentException("Requested dimensions are too small: " + width + 'x' +height);}ErrorCorrectionLevel errorCorrectionLevel = ErrorCorrectionLevel.L;int quietZone = QUIET_ZONE_SIZE;if (hints != null) {if (hints.containsKey(EncodeHintType.ERROR_CORRECTION)) {errorCorrectionLevel = ErrorCorrectionLevel.valueOf(hints.get(EncodeHintType.ERROR_CORRECTION).toString());}if (hints.containsKey(EncodeHintType.MARGIN)) {quietZone = Integer.parseInt(hints.get(EncodeHintType.MARGIN).toString());}}QRCode code = Encoder.encodeQRCode(contents, errorCorrectionLevel, hints);return renderResult(code, width, height, quietZone);}

继续追踪进入Encoder的encode方法。

去掉一些不需要的验证，把appendBytes方法改写：

public static QRCode encodeQRCode(byte[] content, ErrorCorrectionLevel ecLevel,Map<EncodeHintType,?> hints) throws WriterException {// 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.Mode mode = Mode.BYTE;// This will store the header information, like mode and// length, as well as "header" segments like an ECI segment.BitArray headerBits = new BitArray();// Append the FNC1 mode header for GS1 formatted data if applicableboolean hasGS1FormatHint = hints != null && hints.containsKey(EncodeHintType.GS1_FORMAT);if (hasGS1FormatHint && Boolean.valueOf(hints.get(EncodeHintType.GS1_FORMAT).toString())) {// GS1 formatted codes are prefixed with a FNC1 in first position mode headerappendModeInfo(Mode.FNC1_FIRST_POSITION, headerBits);}// (With ECI in place,) Write the mode markerappendModeInfo(mode, headerBits);// Collect data within the main segment, separately, to count its size if needed. Don't add it to// main payload yet.BitArray dataBits = new BitArray();for (byte b : content) {dataBits.appendBits(b, 8);}//二维码的版本从21×21至177×177总共有40个版本，不同的版本可编码的总数据量不同，不指定则自行根据输入的数据量选择最适合的版本。Version version;if (hints != null && hints.containsKey(EncodeHintType.QR_VERSION)) {int versionNumber = Integer.parseInt(hints.get(EncodeHintType.QR_VERSION).toString());version = Version.getVersionForNumber(versionNumber);int bitsNeeded = calculateBitsNeeded(mode, headerBits, dataBits, version);if (!willFit(bitsNeeded, version, ecLevel)) {throw new WriterException("Data too big for requested version");}} else {version = recommendVersion(ecLevel, mode, headerBits, dataBits);}BitArray headerAndDataBits = new BitArray();headerAndDataBits.appendBitArray(headerBits);// Find "length" of main segment and write itint numLetters = dataBits.getSizeInBytes();appendLengthInfo(numLetters, version, mode, headerAndDataBits);// Put data together into the overall payloadheaderAndDataBits.appendBitArray(dataBits);Version.ECBlocks ecBlocks = version.getECBlocksForLevel(ecLevel);int numDataBytes = version.getTotalCodewords() - ecBlocks.getTotalECCodewords();// Terminate the bits properly.terminateBits(numDataBytes, headerAndDataBits);// Interleave data bits with error correction code.BitArray finalBits = interleaveWithECBytes(headerAndDataBits,version.getTotalCodewords(),numDataBytes,ecBlocks.getNumBlocks());QRCode qrCode = new QRCode();qrCode.setECLevel(ecLevel);qrCode.setMode(mode);qrCode.setVersion(version);//  Choose the mask pattern and set to "qrCode".int dimension = version.getDimensionForVersion();ByteMatrix matrix = new ByteMatrix(dimension, dimension);int maskPattern = chooseMaskPattern(finalBits, ecLevel, version, matrix);qrCode.setMaskPattern(maskPattern);// Build the matrix and set it to "qrCode".MatrixUtil.buildMatrix(finalBits, ecLevel, version, maskPattern, matrix);qrCode.setMatrix(matrix);return qrCode;}

appendBytes方法实际上是调用了append8BitBytes方法（纯英文、数字、日语汉字不是），上面重写的方法中直接把append8BitBytes方法内的代码复制了进去，appendBytes的具体代码不贴了，append8BitBytes方法代码如下：

从这里可以看到，字符串实际上最终是转成了byte数组，所以我们直接传byte数组是可以的。

二维码解码

二维码生成完了接下来就是解码了，new MultiFormatReader().decode()返回Result对象，不要使用Result对象的getText方法获取数据，会把byte数组直接转成String，使用rawBytes方法获取byte数组，
byte数组含有zxing在生成二维码时附加的一些信息，需要进行解析获取原始的byte数组。对zxing源码进行分析，实际是可以直接获取到原始的byte数组的，zxing的代码不贴了，MultiFormatReader中把decode改写：

public Result decodeQRCode(BinaryBitmap image, Map<DecodeHintType,?> hints) throws NotFoundException {QRCodeReader reader = new QRCodeReader();this.readers = new Reader[] {reader};try {return  reader.decodeQRCode(image, hints);} catch (Exception e) {e.printStackTrace();}throw NotFoundException.getNotFoundInstance();}

进入QRCodeReader把decode改写：

public final Result decodeQRCode(BinaryBitmap image, Map<DecodeHintType,?> hints) throws NotFoundException, ChecksumException, FormatException {DetectorResult detectorResult = new Detector(image.getBlackMatrix()).detect(hints);DecoderResult decoderResult = decoder.decode(detectorResult.getBits(), hints);return new Result(decoderResult.getText(), decoderResult.getByteSegments().get(0), detectorResult.getPoints(), BarcodeFormat.QR_CODE);}

改写完就可以直接使用Result.getRawBytes()获取原始byte数组了，这里实际上就是Result的rawBytes
本应接收decoderResult.getRawBytes()，替换为了decoderResult.getByteSegments().get(0)，decoderResult.getByteSegments().get(0)就是原始的byte数组。

为了不影响原有功能，所有的改写都是新建的方法。