Android CameraX和HyperLPR3配合使用

实现的功能

HyperLPR3在实时图像预览里面，调用SDK识别摄像机实时图像里面的车牌号，需要用到图片缓存区。CameraX应该按照如下代码使用。

注意

图片必须使用YuvImage压缩写入ByteArrayOutputStream，然后转数组，把数组给HyperLPR3.getInstance().plateRecognition的第一个参数。才能识别出来摄像机实时图像里面的车牌。

private void startCamera() {
    ListenableFuture<ProcessCameraProvider> cameraProviderFuture =
            ProcessCameraProvider.getInstance(this);
    cameraProviderFuture.addListener(() -> {
        try {
            ProcessCameraProvider cameraProvider = cameraProviderFuture.get();
            Preview preview = new Preview.Builder().build();
            preview.setSurfaceProvider(previewView.getSurfaceProvider());
            CameraSelector cameraSelector = new CameraSelector.Builder()
                    .requireLensFacing(CameraSelector.LENS_FACING_BACK)
                    .build();
            ImageAnalysis imageAnalysis =
                    new ImageAnalysis.Builder()
                            .setTargetResolution(new Size(1920, 1080))
                            .setBackpressureStrategy(ImageAnalysis.STRATEGY_KEEP_ONLY_LATEST)
                            .build();
            ExecutorService singleThreadExecutor = Executors.newCachedThreadPool();
            imageAnalysis.setAnalyzer(singleThreadExecutor, image -> {
                ImageProxy.PlaneProxy[] planes = image.getPlanes();
                new Thread(() -> {
                    ByteBuffer yBuffer = planes[0].getBuffer();
                    ByteBuffer uBuffer = planes[1].getBuffer();
                    ByteBuffer vBuffer = planes[2].getBuffer();
                    int ySize = yBuffer.remaining();
                    int uSize = uBuffer.remaining();
                    int vSize = vBuffer.remaining();
                    byte[] nv21 = new byte[ySize + uSize + vSize];
                    yBuffer.get(nv21, 0, ySize);
                    vBuffer.get(nv21, ySize, vSize);
                    uBuffer.get(nv21, ySize + vSize, uSize);
                    YuvImage yuvImage = new YuvImage(nv21, ImageFormat.NV21, image.getWidth(), image.getHeight(), null);
                    //输出流
                    ByteArrayOutputStream out = new ByteArrayOutputStream();
                    //压缩写入out
                    yuvImage.compressToJpeg(new Rect(0, 0, yuvImage.getWidth(), yuvImage.getHeight()), 50, out);
                    //转数组
                    byte[] imageBytes = out.toByteArray();
                    Plate[] plates = HyperLPR3.getInstance().plateRecognition(
                            imageBytes,
                            image.getHeight(),
                            image.getWidth(),
                            HyperLPR3.CAMERA_ROTATION_270,
                            HyperLPR3.STREAM_YUV_NV21);
                    if (0 < plates.length) {
                        for (Plate plate : plates) {
                            String pStr = plate.getCode();
                            //plateTv是个textview控件，跨线程了，所以用runOnUiThread
                            runOnUiThread(() -> plateTv.setText(pStr));
                        }
                    }
                    image.close();
                }).start();
            });
            //绑定前先解绑
            cameraProvider.unbindAll();
            cameraProvider.bindToLifecycle(this, cameraSelector, imageAnalysis, preview);
        } catch (InterruptedException | ExecutionException e) {
            Toast.makeText(context, e.getMessage(), Toast.LENGTH_LONG).show();
        }
    }, ContextCompat.getMainExecutor(this));
}