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Android平台生成二维码并实现扫描 & 识别功能

2019-12-12 06:13:21
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1.二维码的前世今生

“二维条码/二维码(2-dimensional bar code)是用某种特定的几何图形按一定规律在平面(二维方向上)分布的黑白相间的图形记录数据符号信息的;在代码编制上巧妙地利用构成计算机内部逻辑基础的“0”、“1”比特流的概念,使用若干个与二进制相对应的几何形体来表示文字数值信息,通过图象输入设备或光电扫描设备自动识读以实现信息自动处理:它具有条码技术的一些共性:每种码制有其特定的字符集;每个字符占有一定的宽度;具有一定的校验功能等。同时还具有对不同行的信息自动识别功能、及处理图形旋转变化点。 [1] ”

上面是百度百科的解释。既然有二维码,那么肯定有一维码。

一维码。最为常见的就是食品 & 书本后面的条码。

条码起源与20世纪40年代,后来在1970年 UPC码发明,并开始广泛应用与食品包装。

具体的介绍可以看百度百科 一维码。

其实二维码与一维码本质上是类似的,就跟一维数组和二维数组一样。

2.二维码的java支持库

为了让java或者说android方便继承条码的功能,google就开发了一个zxing的库:

https://github.com/zxing/zxing

3.生成二维码

public class EncodeThread {public static void encode(final String url, final int width, final int height, final EncodeResult result) {if (result == null) {return;}if (TextUtils.isEmpty(url)) {result.onEncodeResult(null);return;}new Thread() {@Overridepublic void run() {try {MultiFormatWriter writer = new MultiFormatWriter();Hashtable<EncodeHintType, String> hints = new Hashtable<>();hints.put(EncodeHintType.CHARACTER_SET, "utf-8");BitMatrix bitMatrix = writer.encode(url, BarcodeFormat.QR_CODE, width, height, hints);Bitmap bitmap = parseBitMatrix(bitMatrix);result.onEncodeResult(bitmap);return;} catch (WriterException e) {e.printStackTrace();}result.onEncodeResult(null);}}.start();}/*** 生成二维码内容<br>** @param matrix* @return*/public static Bitmap parseBitMatrix(BitMatrix matrix) {final int QR_WIDTH = matrix.getWidth();final int QR_HEIGHT = matrix.getHeight();int[] pixels = new int[QR_WIDTH * QR_HEIGHT];//this we using qrcode algorithmfor (int y = 0; y < QR_HEIGHT; y++) {for (int x = 0; x < QR_WIDTH; x++) {if (matrix.get(x, y)) {pixels[y * QR_WIDTH + x] = 0xff000000;} else {pixels[y * QR_WIDTH + x] = 0xffffffff;}}}Bitmap bitmap = Bitmap.createBitmap(QR_WIDTH, QR_HEIGHT, Bitmap.Config.ARGB_8888);bitmap.setPixels(pixels, 0, QR_WIDTH, 0, 0, QR_WIDTH, QR_HEIGHT);return bitmap;}public interface EncodeResult {void onEncodeResult(Bitmap bitmap);}} 

zxing 支持很多条码格式:我们这里使用QR_CODE码。也就是我们常见的微信里面的二维码。

我们先来分析下这段代码:

MultiFormatWriter writer = new MultiFormatWriter();

这个是一个工具类,把所有支持的几个write写在里面了。

public BitMatrix encode(String contents,BarcodeFormat format,int width, int height,Map<EncodeHintType,?> hints) throws WriterException {Writer writer;switch (format) {case EAN_8:writer = new EAN8Writer();break;case UPC_E:writer = new UPCEWriter();break;case EAN_13:writer = new EAN13Writer();break;case UPC_A:writer = new UPCAWriter();break;case QR_CODE:writer = new QRCodeWriter();break;case CODE_39:writer = new Code39Writer();break;case CODE_93:writer = new Code93Writer();break;case CODE_128:writer = new Code128Writer();break;case ITF:writer = new ITFWriter();break;case PDF_417:writer = new PDF417Writer();break;case CODABAR:writer = new CodaBarWriter();break;case DATA_MATRIX:writer = new DataMatrixWriter();break;case AZTEC:writer = new AztecWriter();break;default:throw new IllegalArgumentException("No encoder available for format " + format);}return writer.encode(contents, format, width, height, hints);} 

这是官方最新支持的格式,具体看引入的jar里面支持的格式。

对与bitmatrix的结果,通过摸个算法,设置每个点白色,或者黑色。

最后创建一张二维码的图片。

4.识别二维码

如何从一张图片上面,识别二维码呢:

public class ReDecodeThread {public static void encode(final Bitmap bitmap, final ReDecodeThreadResult listener) {if (listener == null) {return;}if (bitmap == null) {listener.onReDecodeResult(null);return;}new Thread() {@Overridepublic void run() {try {MultiFormatReader multiFormatReader = new MultiFormatReader();BitmapLuminanceSource source = new BitmapLuminanceSource(bitmap);BinaryBitmap bitmap1 = new BinaryBitmap(new HybridBinarizer(source));Result result1 = multiFormatReader.decode(bitmap1);listener.onReDecodeResult(result1.getText());return;} catch (NotFoundException e) {e.printStackTrace();}listener.onReDecodeResult(null);}}.start();}public interface ReDecodeThreadResult {void onReDecodeResult(String url);}} 

过程也是很简单,使用MultiFormatReader来分析图片,这里不需要缺人图片的条码格式。

如果分析下源码,就是依次使用每种格式的reader来分析,直到找到合适的为止。

当然回了能够把Bitmap转化成Bitmatrix,然后在分析。

public final class BitmapLuminanceSource extends LuminanceSource{private final byte[] luminances;public BitmapLuminanceSource(String path) throws FileNotFoundException {this(loadBitmap(path));}public BitmapLuminanceSource(Bitmap bitmap) {super(bitmap.getWidth(), bitmap.getHeight());int width = bitmap.getWidth();int height = bitmap.getHeight();int[] pixels = new int[width * height];bitmap.getPixels(pixels, 0, width, 0, 0, width, height);// In order to measure pure decoding speed, we convert the entire image// to a greyscale array// up front, which is the same as the Y channel of the// YUVLuminanceSource in the real app.luminances = new byte[width * height];for (int y = 0; y < height; y++) {int offset = y * width;for (int x = 0; x < width; x++) {int pixel = pixels[offset + x];int r = (pixel >> 16) & 0xff;int g = (pixel >> 8) & 0xff;int b = pixel & 0xff;if (r == g && g == b) {// Image is already greyscale, so pick any channel.luminances[offset + x] = (byte) r;} else {// Calculate luminance cheaply, favoring green.luminances[offset + x] = (byte) ((r + g + g + b) >> 2);}}}}@Overridepublic byte[] getRow(int y, byte[] row) {if (y < 0 || y >= getHeight()) {throw new IllegalArgumentException("Requested row is outside the image: " + y);}int width = getWidth();if (row == null || row.length < width) {row = new byte[width];}System.arraycopy(luminances, y * width, row, 0, width);return row;}// Since this class does not support cropping, the underlying byte array// already contains// exactly what the caller is asking for, so give it to them without a copy.@Overridepublic byte[] getMatrix() {return luminances;}private static Bitmap loadBitmap(String path) throws FileNotFoundException {Bitmap bitmap = BitmapFactory.decodeFile(path);if (bitmap == null) {throw new FileNotFoundException("Couldn't open " + path);}return bitmap;}} 

5.扫描二维码

扫描二维码,其实比上面只多了一步,就是把camera获取的东西直接转换,然后进行识别。

public void requestPreviewFrame(Handler handler, int message) {if (camera != null && previewing) {previewCallback.setHandler(handler, message);if (useOneShotPreviewCallback) {camera.setOneShotPreviewCallback(previewCallback);} else {camera.setPreviewCallback(previewCallback);}}} 

首先把camera预览的数据放入previewCallback中。

final class PreviewCallback implements Camera.PreviewCallback public void onPreviewFrame(byte[] data, Camera camera) {Point cameraResolution = configManager.getCameraResolution();if (!useOneShotPreviewCallback) {camera.setPreviewCallback(null);}if (previewHandler != null) {Message message = previewHandler.obtainMessage(previewMessage, cameraResolution.x,cameraResolution.y, data);message.sendToTarget();previewHandler = null;} else {Log.d(TAG, "Got preview callback, but no handler for it");}} 

可以看到,预览的数据data,回传递过来,然后handler的方式传递出去。

接收data的地方:

@Overridepublic void handleMessage(Message message) {switch (message.what) {case R.id.decode://Log.d(TAG, "Got decode message");decode((byte[]) message.obj, message.arg1, message.arg2);break;case R.id.quit:Looper.myLooper().quit();break;}} 

然后是decode data

private void decode(byte[] data, int width, int height) {long start = System.currentTimeMillis();Result rawResult = null;//modify herebyte[] rotatedData = new byte[data.length];for (int y = 0; y < height; y++) {for (int x = 0; x < width; x++)rotatedData[x * height + height - y - 1] = data[x + y * width];}int tmp = width; // Here we are swapping, that's the difference to #11width = height;height = tmp;PlanarYUVLuminanceSource source = CameraManager.get().buildLuminanceSource(rotatedData, width, height);BinaryBitmap bitmap = new BinaryBitmap(new HybridBinarizer(source));try {rawResult = multiFormatReader.decodeWithState(bitmap);} catch (ReaderException re) {// continue} finally {multiFormatReader.reset();}if (rawResult != null) {long end = System.currentTimeMillis();Log.d(TAG, "Found barcode (" + (end - start) + " ms):/n" + rawResult.toString());Message message = Message.obtain(activity.getHandler(), R.id.decode_succeeded, rawResult);Bundle bundle = new Bundle();bundle.putParcelable(DecodeThread.BARCODE_BITMAP, source.renderCroppedGreyscaleBitmap());message.setData(bundle);//Log.d(TAG, "Sending decode succeeded message...");message.sendToTarget();} else {Message message = Message.obtain(activity.getHandler(), R.id.decode_failed);message.sendToTarget();}} 

当把camera上的图片转换成BinaryBitmap以后,剩下的事情,就更直接从图片识别是一样的。

PlanarYUVLuminanceSource source = CameraManager.get().buildLuminanceSource(rotatedData, width, height);
BinaryBitmap bitmap = new BinaryBitmap(new HybridBinarizer(source));

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