Android CameraX - manually change exposure compensation?

Question

I'm using CameraX for my project. I have created preview useCase and capture useCase.

final CameraSelector cameraSelector = new CameraSelector.Builder().requireLensFacing(lensFacing).build();

        previewBuilder = new Preview.Builder()
            .setTargetResolution(targetOutputSize)
            .setTargetRotation(rotation);

        preview = previewBuilder.build();

        final ImageCapture.Builder imageCaptureBuilder = new ImageCapture.Builder()
            .setCaptureMode(ImageCapture.CAPTURE_MODE_MINIMIZE_LATENCY)
            .setTargetResolution(targetOutputSize)
            .setTargetRotation(rotation);

        imageCapture = imageCaptureBuilder.build();

Everything works fine. Now, I need to add functionality to manually change exposure compensation, but I can't find any reference in official documentation or anywhere else how to do this. Is it possible with CameraX, or I need to switch to Camera2 API?

Please, any help is welcome.

score 5 · Accepted Answer · answered Sep 25 '20 at 00:12

There is new version of CameraX library.

def camerax_version = '1.0.0-beta09'

Firstly add those dependencies to gradle file.

// CameraX core library
implementation "androidx.camera:camera-core:$camerax_version"

// CameraX Camera2 extensions
implementation "androidx.camera:camera-camera2:$camerax_version"

This version supports Exposure compensation which can be adjusted in runtime. First create preview and takePicure use cases, and then bind those use cases to cameraProvider.

 camera = cameraProvider.bindToLifecycle(this, cameraSelector, preview, imageCapture);

Now we have camera instance and it can be used to retrive CameraInfo, and from CameraInfo, we retrive ExposureState.

ExposureState exposureState = camera.getCameraInfo().getExposureState();

We can use exposureState to check if exposure compensation is supported on device

if (!exposureState.isExposureCompensationSupported()) return;

Next we need to get ExposureCompensation Range

Range<Integer> range = exposureState.getExposureCompensationRange();

Finally, we can set ExposureCompensation index in following way

 if (range.contains(index))
     camera.getCameraControl().setExposureCompensationIndex(index);

score 1 · Answer 2 · answered Sep 02 '20 at 19:05

1

Looks like there is a Camera2Interop class under the CameraX API which allows you to internally change the values. This is the official documentation: Camera2Interop.Extender

Before building your ImageCapture, add this:

Camera2Interop.Extender(imageCaptureBuilder)
    .setCaptureRequestOption(CaptureRequest.CONTROL_AE_EXPOSURE_COMPENSATION, value);

answered Sep 02 '20 at 19:05

Bingostew

138
6

It needs to be changeable during the use of camera. For example, on camera UI we need to have two buttons "+" and "-" and clicking on those buttons to change exposure compensation. Currently, this is not possible on CameraX, but I found that branch with this feature was merged into master on CameraX and I hope that it will be soon in release version. – Šemsudin Tafilović Sep 04 '20 at 20:27

score 0 · Answer 3 · answered Jun 19 '21 at 16:12

In case you want to know when the camera completed changing the exposure settings, do something like (camerax_version = '1.0.0'):

    lateinit var myCameraExposureListener: ListenableFuture<Int>

and then

        myCameraExposureListener =
        myCameraControl!!.setExposureCompensationIndex(exposureCompensationIndex);

    myCameraExposureListener.addListener({
        try {
            Log.v(TAG, "Changing Exposure Settings Completed")
        } catch (exception: Exception) {
            Log.v(TAG, "Changing Exposure Settings Failed")
        }
    }, ContextCompat.getMainExecutor(context) )

Android CameraX - manually change exposure compensation?

3 Answers3