Question

如何在拍摄照片时从Android手机获取AutoExposureCompensation级别（亮度）？

我可以拍照。我可以访问摄像机的参数，包括曝光补偿（当我检查时总是为零），但我需要在拍摄照片时获得AE补偿级别，而不是之前和之后。

背景：我希望在特定时间拍摄的所有照片都使用相同的AE补偿等级拍摄照片。我不希望Android相机通常会对曝光级别或白平衡进行数百次调整。我想获得一次，并为所有后续照片设置相同的设置。

我曾尝试对图片，OpenCV，片段等使用“意图”。我似乎无法使用其中任何一种获得AE补偿设置。这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);
    }
}

以下是Android View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）足以满足您的需求。

来源：https://developer.android.com/reference/android/hardware/camera2/CaptureRequest.html#CONTROL_AE_LOCK

由于相机设备具有飞行中请求的管道，因此   锁定的设置不一定与设置相对应   最新的捕获结果中出现的数据来自于   相机设备，因为可能有额外的捕获和AE更新   甚至在结果发出之前就已经发生了。如果申请是   在自动和手动控制之间切换，并希望消除   切换过程中出现任何闪烁，建议采用以下步骤：


以自动曝光模式开始：

锁定AE

等待输出具有AE锁定的第一个结果

将该结果中的曝光设置复制到请求中，将请求设置为手动AE

提交捕获请求，继续根据需要运行手动AE。

另外，根据AE模式（相同来源）的描述

当设置为任何ON模式时，摄像机选择的值设备自动曝光例程，用于给定的重写字段捕获将在其CaptureResult中提供。

因此，一旦您完成第一个CaptureRequest，您可以使用以下回调中的TotalCaptureResult：

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

Answer 2

好的，问题出现了如何在编写代码来控制Android相机时具体设置曝光，传感器灵敏度和其他变量。这只适用于Lollipop或更高版本。要发布很多代码，但我会尝试加入亮点

简而言之，我使用带有CameraManager的TextureView（AutoFitTextureView）。当我打开相机时，我调用了一个名为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，我自己也会为发现类似问题的人自己回答这个问题。

Manish接近他的回答，但即使在onCaptureSession事件中使用，CONTROL_AE_EXPOSURE_COMPENSATION也只返回0（零），这是没用的;这只是相机的默认起始值。

但是，CameraCaptureSession.CaptureCallback（onCaptureSession事件）可以让您从SENSOR_EXPOSURE_TIME和SENSOR_SENSITIVITY获取值，以创建解决使用Android相机的自动曝光问题的方法。

以下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());

            }
        };

这是我调试器的结果图片：

如何在拍摄照片时通过Java获取Android手机摄像头的曝光补偿等级？

3 个答案: