[camerax] Implement focus mode configuration

[camsim99]

In the camera plugin API, there are two methods related to the configuration of the focus mode. These should be implemented in the CameraX plugin:

• setFocusMode(....)
• setFocusPoint(..)

[jstevensconverus]

Hello, is there an update on this issue? My company is unable to use this plugin until the issue is resolved.

[camsim99]

Hello, is there an update on this issue? My company is unable to use this plugin until the issue is resolved.

I have just begun working on this feature; will update here when a PR is submitted for review.

[camsim99]

Looking into how we may be able to replicate auto/locked Flutter-defined focus modes and found some helpful discussion sthat I likely will need to implement this: https://groups.google.com/a/android.com/g/camerax-developers/c/VRsER_nHeHM?pli=1, https://groups.google.com/a/android.com/g/camerax-developers/c/h0Q4Al8TXmc?pli=1

[camsim99]

Working on implementing setFocusMode and it's not clear to me how to implement locked versus auto mode, so I want to write out my thoughts as of now so I can correct my assumptions as needed with this as a baseline.

Locked mode:
To implement locked mode in camera_android, we did something like

// When locking the auto-focus the camera device should do a one-time focus and afterwards
// set the auto-focus to idle. This is accomplished by setting the CONTROL_AF_MODE to
// CONTROL_AF_MODE_AUTO.
captureRequestBuilder.set(CaptureRequest.CONTROL_AF_MODE, CaptureRequest.CONTROL_AF_MODE_AUTO);
captureRequestBuilder.set(
  CaptureRequest.CONTROL_AF_TRIGGER, CaptureRequest.CONTROL_AF_TRIGGER_START); 
captureSession.capture(captureRequestBuilder.build(), null, backgroundHandler);
captureRequestBuilder.set(
  CaptureRequest.CONTROL_AF_TRIGGER, CameraMetadata.CONTROL_AF_TRIGGER_IDLE);
captureSession.setRepeatingRequest(
  captureRequestBuilder.build(), null, backgroundHandler);

It's my understanding that this is what is going on under the hood in CameraX when we set an AF MeteringPoint via startFocusAndMetering.

Auto mode:
To implement auto mode in camera_android, we did something like

captureRequestBuilder.set(
    CaptureRequest.CONTROL_AF_MODE,
    recordingVideo
        ? CaptureRequest.CONTROL_AF_MODE_CONTINUOUS_VIDEO
        : CaptureRequest.CONTROL_AF_MODE_CONTINUOUS_PICTURE);
// Cancel existing AF state.
captureRequestBuilder.set(
    CaptureRequest.CONTROL_AF_TRIGGER, CameraMetadata.CONTROL_AF_TRIGGER_CANCEL);
captureSession.capture(captureRequestBuilder.build(), null, backgroundHandler);
// Set AF state to idle again.
captureRequestBuilder.set(
    CaptureRequest.CONTROL_AF_TRIGGER, CameraMetadata.CONTROL_AF_TRIGGER_IDLE);
captureSession.capture(captureRequestBuilder.build(), null, backgroundHandler);

To implement this with CameraX, I believe we will need to remove any AF MeteringPoints from any running FocusMeteringActions set via startFocusandMetering or, if we have only set AF MeteringPoints, cancel focus and metering altogether. This is because the continuous auto focus mode is CameraX's default mode.

[camsim99]

It turns out that CameraX always uses auto focus mode, preferring CaptureRequest.CONTROL_AF_MODE for CaptureRequest. CONTROL_AF_MODE_AUTO, but may fallback to CONTROL_AF_MODE_CONTINUOUS_VIDEO/CONTROL_AF_MODE_CONTINUOUS_PICTURE based on the source code, and never sets CaptureRequest.CONTROL_AF_TRIGGER to CameraMetadata.CONTROL_AF_TRIGGER_IDLE.

To work around this, I'm going to (1) try implementing locked focus mode with Camera2 interop, and depending on the results of that and digging deeper into the philosophy of CameraX only using autofocus mode, (2) consider the pros/cons of not implementing locked focus mode.

[camsim99]

I just tried using Camera2CameraControl to manually lock the focus mode, with two attempts:

Attempt 1 (fail):
I added the capture request options CameraMetadata.CONTROL_AF_TRIGGER_IDLE for CaptureRequest.CONTROL_AF_TRIGGER with Camera2CameraControl.addCaptureRequestOptions, and I still saw autofocus.

Attempt 2 (success?):
I set the capture request options CaptureRequest.CONTROL_AF_MODE_AUTO for CaptureRequest.CONTROL_AF_MODE and CameraMetadata.CONTROL_AF_TRIGGER_IDLE for CaptureRequest.CONTROL_AF_TRIGGER with Camera2CameraControl.setCaptureRequestOptions, and it actually seemed to work, though I wonder how this may conflict with the default behavior.

[github-actions]

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