Question

我在Android上工作，我试图捕捉图片而不显示任何预览。我试着通过上课来简化这个过程。它正在工作，但所有的照片都非常黑暗。这是我的班级：

public class Cam {
private Context context;
private CameraManager manager;
private CameraDevice camera;
private CameraCaptureSession session;
private ImageReader reader;
public static String FRONT="-1";
public static String BACK="-1";
private boolean available=true;
private String filepath;

private static final String NO_CAM = "No camera found on device!";
private static final String ERR_CONFIGURE = "Failed configuring session";
private static final String ERR_OPEN = "Can't open the camera";
private static final String CAM_DISCONNECT = "Camera disconnected";
private static final String FILE_EXIST = "File already exist";

private static final SparseIntArray ORIENTATIONS = new SparseIntArray();
static {
    ORIENTATIONS.append(Surface.ROTATION_0, 90);
    ORIENTATIONS.append(Surface.ROTATION_90, 0);
    ORIENTATIONS.append(Surface.ROTATION_180, 270);
    ORIENTATIONS.append(Surface.ROTATION_270, 180);
}

public Cam(Context context) throws CameraAccessException {
    this.context = context;
    this.manager = (CameraManager) context.getSystemService(Context.CAMERA_SERVICE);
    String ids[] = manager.getCameraIdList();
    if(ids.length==2){
        BACK=ids[0];
        FRONT=ids[1];
    }
    else if(ids.length==1){
        BACK=ids[0];
    }
    else{
        available=false;
        throw new CameraAccessException(-1, NO_CAM);
    }
}

public void takePicture(String camId, String filepath) throws CameraAccessException {
    if(available){
        this.filepath=filepath;
        StreamConfigurationMap map = manager.getCameraCharacteristics(camId).get(CameraCharacteristics.SCALER_STREAM_CONFIGURATION_MAP);
        Size largest = Collections.max(Arrays.asList(map.getOutputSizes(ImageFormat.JPEG)), new CompareSizesByArea());
        reader=ImageReader.newInstance(largest.getWidth(), largest.getHeight(), ImageFormat.JPEG, 1);
        reader.setOnImageAvailableListener(imageListener, null);
        manager.openCamera(camId, cameraStateCallback, null);
    }
    else
        throwError(NO_CAM);
}

private CameraDevice.StateCallback cameraStateCallback = new CameraDevice.StateCallback() {
    @Override
    public void onOpened(CameraDevice camera) {
        Cam.this.camera=camera;
        try {
            camera.createCaptureSession(Collections.singletonList(reader.getSurface()), sessionStateCallback, null);
        } catch (CameraAccessException e) {
            throwError(e.getMessage());
        }
    }

    @Override
    public void onDisconnected(CameraDevice camera) {
        throwError(CAM_DISCONNECT);
    }

    @Override
    public void onError(CameraDevice camera, int error) {
        throwError(ERR_OPEN);
    }
};

private CameraCaptureSession.StateCallback sessionStateCallback = new CameraCaptureSession.StateCallback() {
    @Override
    public void onConfigured(CameraCaptureSession session) {
        Cam.this.session=session;
        try {
            CaptureRequest.Builder request = camera.createCaptureRequest(CameraDevice.TEMPLATE_STILL_CAPTURE);
            request.set(CaptureRequest.CONTROL_AF_MODE, CaptureRequest.CONTROL_AF_MODE_CONTINUOUS_PICTURE);
            request.addTarget(reader.getSurface());
            int rotation = ((WindowManager)context.getSystemService(Context.WINDOW_SERVICE)).getDefaultDisplay().getRotation();
            request.set(CaptureRequest.JPEG_ORIENTATION, ORIENTATIONS.get(rotation));
            session.capture(request.build(), captureCallback, null);
        } catch (CameraAccessException e) {
            throwError(e.getMessage());
        }
    }

    @Override
    public void onConfigureFailed(CameraCaptureSession session) {
        throwError(ERR_CONFIGURE);
    }
};

private CameraCaptureSession.CaptureCallback captureCallback = new CameraCaptureSession.CaptureCallback() {
    @Override
    public void onCaptureFailed(CameraCaptureSession session, CaptureRequest request, CaptureFailure failure) {
        super.onCaptureFailed(session, request, failure);
        throwError(failure.toString());
    }
};

private ImageReader.OnImageAvailableListener imageListener = new ImageReader.OnImageAvailableListener() {
    @Override
    public void onImageAvailable(ImageReader reader) {
        Image image = reader.acquireLatestImage();
        try {
            File file = saveImage(image);
            // Send file via a listener
            closeCamera();
        } catch (IOException e) {
            throwError(e.getMessage());
        }
        reader.close();
    }
};

private File saveImage(Image image) throws IOException {
    File file = new File(filepath);
    if (file.exists()) {
        throwError(FILE_EXIST);
        return null;
    }
    else {
        ByteBuffer buffer = image.getPlanes()[0].getBuffer();
        byte[] bytes = new byte[buffer.remaining()];
        buffer.get(bytes);
        FileOutputStream output = new FileOutputStream(file);
        output.write(bytes);
        image.close();
        output.close();
        return file;
    }
}

static class CompareSizesByArea implements Comparator<Size> {
    @Override
    public int compare(Size lhs, Size rhs) {
        return Long.signum((long) lhs.getWidth() * lhs.getHeight() - (long) rhs.getWidth() * rhs.getHeight());
    }
}

private void closeCamera(){
    if(session!=null) {session.close();}
    if(reader!=null) {reader.close();}
    if(camera!=null) {camera.close();}
}

然后我在我的Activity中调用Cam对象：

Cam cam = new Cam(MainActivity.this);
cam.takePicture(Cam.BACK, "/sdcard/pic.jpg");

当图片可用时，侦听器会阻止MainActivity，但我删除了代码以清除它。

我不知道自己做错了什么，照片真的很黑。也许是旗帜或其他......任何帮助将不胜感激。

修改工人阶级：https://github.com/omaflak/Android-Camera2-Library/blob/master/ezcam/src/main/java/me/aflak/ezcam/EZCam.java

示例：https://github.com/omaflak/Android-Camera2-Library/blob/master/app/src/main/java/me/aflak/libraries/MainActivity.java

Answer 1

如果您发送给相机的唯一捕获请求是最终图片的捕获请求，这就不足为奇了。

相机自动曝光，对焦和白平衡程序通常需要一两秒或两个流缓冲才能收敛到良好的效果。

虽然您不需要在屏幕上绘制预览，但最简单的方法是首先运行针对虚拟SurfaceTexture的重复请求一两秒钟，然后触发JPEG捕获。您可以直接进行JPEG捕获，但JPEG捕获速度很慢，因此您需要更长的时间进行收敛（此外，相机实现更有可能出现重复JPEG捕获和获得良好曝光的错误，而不是典型的预览。）

因此，使用随机纹理ID参数创建一个虚拟SurfaceTexture：

private SurfaceTexture mDummyPreview = new SurfaceTexture(1);
private Surface mDummySurface = new Surface(mDummyPreview);

并在会话配置中包含Surface。配置会话后，创建一个以虚拟预览为目标的预览请求，并在N个捕获结果进入后，提交所需JPEG的捕获请求。你想要试验N，但是大约30帧就足够了。

请注意，您仍然没有处理：

锁定自动对焦以确保JPEG图像清晰
如果要允许闪光灯使用，请运行AE预捕捉以允许闪光测光
让用户知道他们将会捕捉什么，因为没有预览，他们无法将设备瞄准任何事情。

自动对焦锁定和预捕捉触发序列包含在此处的Camera2Basic示例中：https://github.com/googlesamples/android-Camera2Basic，因此您可以查看其中的内容。

Answer 2

也许您可以尝试打开自动曝光模式和自动白平衡：

request.set(CaptureRequest.CONTROL_AE_MODE, CaptureRequest.CONTROL_AE_MODE_ON);
request.set(CaptureRequest.CONTROL_AWB_MODE, CaptureRequest.CONTROL_AWB_MODE_AUTO);

我希望它会有所帮助：）

Answer 3

就我而言，仅FPS配置对我有帮助。并且不要忘了将其放到CaptureRequest.Builder进行预览，也放到CaptureRequest.Builder捕获构建器中。与往常一样，FPS 10或15帧足以拍摄照片和预览。

捕获生成器

// This is the CaptureRequest.Builder that we use to take a picture.
final CaptureRequest.Builder captureBuilder = mCameraDevice.createCaptureRequest(CameraDevice.TEMPLATE_STILL_CAPTURE);
...
setupFPS(captureBuilder);

预览构建器：

// We set up a CaptureRequest.Builder with the output Surface.
mPreviewRequestBuilder = mCameraDevice.createCaptureRequest(CameraDevice.TEMPLATE_PREVIEW);
mPreviewRequestBuilder.addTarget(surface);
                ...
// set FPS rate
setupFPS(mPreviewRequestBuilder);

在哪里设置FPS：

private void setupFPS(CaptureRequest.Builder builder){
        if(fpsRange != null) {
            builder.set(CaptureRequest.CONTROL_AE_TARGET_FPS_RANGE, fpsRange);
        }
}

并使用以下命令初始化FPS：

CameraCharacteristics characteristics = manager.getCameraCharacteristics(cameraId);
try {
                    Range<Integer>[] ranges = characteristics.get(CameraCharacteristics.CONTROL_AE_AVAILABLE_TARGET_FPS_RANGES);
                    if(ranges != null) {
                        for (Range<Integer> range : ranges) {
                            int upper = range.getUpper();
                            Log.i(TAG, "[FPS Range Available]:" + range);
                            if (upper >= 10) {
                                if (fpsRange == null || upper < fpsRange.getUpper()) {
                                    fpsRange = range;
                                }
                            }
                        }
                    }
                } catch (Exception e) {
                    e.printStackTrace();
                }
                Log.i(TAG, "[FPS Range] is:" + fpsRange);

使用Camera2 API的图片非常暗

3 个答案: