当拍摄照片时，如何通过Java从Android手机摄像头获得曝光补偿水平？

Question

当照片拍摄到AutoExposureCompensation时，如何从安卓手机中获取的亮度？

我可以拍张照片。我可以访问相机的参数，包括曝光补偿(当我检查时总是为零)，但我需要获得AE补偿水平在照片拍摄的时刻，而不是在之前和之后。

背景:我希望所有的照片，在一定的时间，使用相同的AE补偿水平的照片是拍摄的。我不想像Android相机那样，对曝光水平或白平衡进行数百次调整。我想得到一次，并设置所有后续的照片，相同的设置。

我尝试使用“意图”的图片，OpenCV，片段等。我似乎无法得到声发射补偿设置与任何这些。下面是我尝试过的最新代码，从JavaCameraView的扩展版本开始：

import org.opencv.android.JavaCameraView;
import android.content.Context;
import android.hardware.Camera;
import android.hardware.Camera.PictureCallback;
import android.hardware.Camera.Size;
import android.util.AttributeSet;
import android.util.Log;
@SuppressWarnings("deprecation")
public class NewJavaCameraView extends JavaCameraView implements PictureCallback {

public int getExposureCompensation(){
    return mCamera.getParameters().getExposureCompensation();
}
 @SuppressWarnings("deprecation")
 public void takePicture(final String fileName) {
    Log.i(TAG, "Taking picture");
    this.mPictureFileName = fileName;

    Camera.Parameters params = mCamera.getParameters();
    int exposureComp = params.getExposureCompensation();
    mCamera.setPreviewCallback(null);

    // PictureCallback is implemented by the current class
    int otherexposureComp =this.getExposureCompensation();
    mCamera.takePicture(null, null, this);
}

 @SuppressWarnings("deprecation")
 @Override
 public void onPictureTaken(byte[] data, Camera camera) {

    Camera.Parameters params = mCamera.getParameters();
    int exposureComp = params.getExposureCompensation();
    int otherexposureComp =this.getExposureCompensation();
    mCamera.startPreview();
    mCamera.setPreviewCallback(this);

    // Write the image in a file (in jpeg format)
    try {
        FileOutputStream fos = new FileOutputStream(mPictureFileName);

        fos.write(data);
        fos.close();

    } catch (java.io.IOException e) {
        Log.e("Picture", "photoCallback", e);
    }
}

下面是Android视图中使用上述类的一些代码：

public class DiscPhoto extends Activity implements CvCameraViewListener2, OnTouchListener {
 private static final String TAG = "OCVSample::Activity";
 private NewJavaCameraView mOpenCvCameraView;
 private List<Size> mResolutionList;

 private BaseLoaderCallback mLoaderCallback = new BaseLoaderCallback(this) {
    @Override
    public void onManagerConnected(int status) {
        switch (status) {
            case LoaderCallbackInterface.SUCCESS:
            {
                Log.i(TAG, "OpenCV loaded successfully");
                mOpenCvCameraView.enableView();
                mOpenCvCameraView.setOnTouchListener(DiscPhoto.this);
            } break;
            default:
            {
                super.onManagerConnected(status);
            } break;
        }
    }
};

public DiscPhoto() {
    Log.i(TAG, "Instantiated new " + this.getClass());
}

/** Called when the activity is first created. */
@Override
public void onCreate(Bundle savedInstanceState) {
    Log.i(TAG, "called onCreate");
    super.onCreate(savedInstanceState);
    getWindow().addFlags(WindowManager.LayoutParams.FLAG_KEEP_SCREEN_ON);

    setContentView(R.layout.activity_disc_photo);

    mOpenCvCameraView = (NewJavaCameraView) findViewById(R.id.discPhotoPage);
    mOpenCvCameraView.setVisibility(SurfaceView.VISIBLE);
    mOpenCvCameraView.setCvCameraViewListener(this);
}

@SuppressLint("SimpleDateFormat")
@Override
public boolean onTouch(View v, MotionEvent event) {
    Log.i(TAG,"onTouch event");
    SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd_HH-mm-ss");
    String currentDateandTime = sdf.format(new Date());
    String fileName = Environment.getExternalStorageDirectory().getPath() +
            "/sample_picture_" + currentDateandTime + ".jpg";
    mOpenCvCameraView.takePicture(fileName);
    Toast.makeText(this, fileName + " saved", Toast.LENGTH_SHORT).show();
    return false;
}

Answer 1

我认为camera2 API (https://developer.android.com/reference/android/hardware/camera2/CaptureRequest.html)将满足您的需要。

来源：LOCK 由于相机设备具有飞行中请求的管道，因此锁定的设置不一定对应于从相机设备接收的最新捕获结果中存在的设置，因为更多的捕获和AE更新可能在发送结果之前就发生了。如果应用程序在自动控制和手动控制之间切换，并希望在切换过程中消除任何闪烁，建议采用以下步骤：

1. 从自动声发射模式开始：
2. 锁声
3. 等待第一个结果被锁定的结果
4. 将该结果的曝光设置复制到请求中，将请求设置为手动AE。
5. 提交捕获请求，继续按需要运行手动AE。

也是根据AE模式的描述(相同的来源)

当设置为任何ON模式时，相机设备自动曝光例程为给定捕获的覆盖字段选择的值将在其CaptureResult中可用。

因此，一旦创建了第一个CaptureRequest，就可以通过以下回调使用TotalCaptureResult：

void onCaptureCompleted (CameraCaptureSession session, 
                CaptureRequest request, 
                TotalCaptureResult result)
{
       int aecompensationlevel = result.get(CaptureResult.CONTROL_AE_EXPOSURE_COMPENSATION)
}

Answer 2

好的，问题是在编写控制Android摄像头的代码时，如何具体地设置曝光、传感器灵敏度和其他变量。这将只适用于棒棒糖或以后。有很多代码要发布，但我会尽量把重点放在

简而言之，我使用TextureView (AutoFitTextureView)和CameraManager。打开相机时，我调用一个名为createPreviewSessions()的void函数

  void openCamera() {
    try {
        mManager.openCamera(mCameraId, new CameraDevice.StateCallback() {
            @Override
            public void onOpened(CameraDevice camera) {
                createPreviewSession();
            }
        }

private void createPreviewSession() {
    try {
        SurfaceTexture texture = mTextureView.getSurfaceTexture();
        assert texture != null;
        texture.setDefaultBufferSize(mPreviewSize.getWidth(), mPreviewSize.getHeight());
        final List<Surface> surfaceList = new ArrayList<>();
        Surface surface = mImageReader.getSurface();
        surfaceList.add(surface);

        mCamera.createCaptureSession(surfaceList, new CameraCaptureSession.StateCallback() {
            @Override
            public void onConfigured(CameraCaptureSession session) {
                mSession = session;

                CaptureRequest request = createRequest(surfaceList, milliSecond, sensorSetting); //module variables
            } ...
       } ...
}
private CaptureRequest createRequest(List<Surface> surfaces, int milliSeconds, int sensorSetting) {
    Log.v("createRequest","here");
    try {
        CaptureRequest.Builder builder = mCamera.createCaptureRequest(CameraDevice.TEMPLATE_PREVIEW);
        builder.set(CaptureRequest.CONTROL_EFFECT_MODE, CameraMetadata.CONTROL_EFFECT_MODE_OFF);
        for (Surface surface : surfaces)
            builder.addTarget(surface);
        int exposureTime = milliSeconds * (milliSecondFactor); //billionth
        CaptureRequestSettings.SetRequestBuilder(builder,CONTROL_AWB_MODE_DAYLIGHT);

        builder.set(CaptureRequest.SENSOR_EXPOSURE_TIME, Long.valueOf(exposureTime));       //set hard values based on settings caught when photo taken
        builder.set(CaptureRequest.SENSOR_SENSITIVITY, Integer.valueOf(sensorSetting));     //same thing
        builder.set(CaptureRequest.CONTROL_AF_MODE, CaptureRequest.CONTROL_AF_MODE_CONTINUOUS_PICTURE);
        builder.set(CaptureRequest.CONTROL_AWB_MODE, CaptureRequest.CONTROL_AWB_MODE_OFF);  //CaptureRequest.CONTROL_AWB_MODE_OFF); //off here just like video mode
        builder.set(CaptureRequest.CONTROL_AE_MODE, CaptureRequest.CONTROL_AE_MODE_OFF);    //off ... don't want auto exposure

        return builder.build();
    } catch (CameraAccessException e) {
        Log.e("CaptureRequest", "CameraAccessException: " +e.getMessage());
    } catch (Exception e) {
        Log.e("CaptureRequest", "Regular Exception: " +e.getMessage());
    }
    Log.v("createRequest","shouldn't get here");
    return null;
}

Answer 3

好的，我会亲自回答这个问题，无论谁发现类似的问题。

Manish接近了他的答案，但是即使在onCaptureSession事件中使用时，CONTROL_AE_EXPOSURE_COMPENSATION也只返回0(0)，这是无用的；这只是摄像机的默认起始值。

然而，CameraCaptureSession.CaptureCallback (onCaptureSession事件)确实允许您从SENSOR_EXPOSURE_TIME和SENSOR_SENSITIVITY中获取值，从而创建一个解决与安卓相机打交道的自动曝光问题的方法。

下面是我使用的代码片段：

private void captureStillPicture() {
    try {
          ...
        CameraCaptureSession.CaptureCallback CaptureCallback
                = new CameraCaptureSession.CaptureCallback() {

            @Override
            public void onCaptureCompleted(@NonNull CameraCaptureSession session,
                                           @NonNull CaptureRequest request,
                                           @NonNull TotalCaptureResult result) {

                long sensorTime= result.get(CaptureResult.SENSOR_EXPOSURE_TIME);
                long sensorSensitivity = result.get(CaptureResult.SENSOR_SENSITIVITY);

                int ONE_SECOND = 1000000000; //1 billion nanoseconds
                int MICRO_SECOND = 1000000;
                int MILLI_SECOND = 1000;
                String exposureText = "";
                if (sensorTime > ONE_SECOND) {
                    exposureText = String.format("%.2f s", sensorTime / 1e9);
                } else if (sensorTime > MILLI_SECOND) {
                    exposureText = String.format("%.2f ms", sensorTime / 1e6);
                } else if (sensorTime > MICRO_SECOND) {
                    exposureText = String.format("%.2f us", sensorTime / 1e3);
                } else {
                    exposureText = String.format("%d ns", sensorTime);
                }

                int aecompensationlevel=result.get(CaptureResult.CONTROL_AE_EXPOSURE_COMPENSATION); //only returns zero
                showToast("Saved: " + mFile +" | " +exposureText );
                Log.d(TAG, mFile.toString());

            }
        };

下面是我的调试器结果的图片：

​

​