VibeCoding/.agents/skills/camerax/references/low-light.md

This guide covers implementing low-light features using Night mode extensions and Low Light Boost (LLB).

Choosing the right tool

Feature	Used for	Implementation	UX impact
Night mode	High-quality stills	ExtensionsManager	Possibly requires user to hold still for several seconds.
LLB, AE mode	Real-time preview or video	Camera2Interop, CameraX utility	Hardware drops the frame rate to increase brightness.
LLB, Play services	Real-time preview and video	SurfaceProcessor	Software-based brightening; maintains a higher frame rate.

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Night mode extension

CameraX Extensions provide access to the device's built-in computational photography pipeline.

Basic setup

To set up the extension, initialize the extension manager:

// Use ListenableFuture.await() extension function for coroutine support
val extensionsManager = ExtensionsManager.getInstanceAsync(context, cameraProvider).await()
if (extensionsManager.isExtensionAvailable(cameraSelector, ExtensionMode.NIGHT)) {
    val nightSelector = extensionsManager.getExtensionEnabledCameraSelector(
        cameraSelector, ExtensionMode.NIGHT
    )
    cameraProvider.bindToLifecycle(lifecycleOwner, nightSelector, imageCapture, preview)
}

Comprehensive features

• Image postview : Display a low-resolution image immediately while the multi-frame processing occurs.

  val imageCapture = ImageCapture.Builder()
      .setPostviewEnabled(true)
      .build()
  

• Extension strength : Let users control the intensity of the night effect.

  // Set the strength of the active extension (e.g. NIGHT mode intensity)
  val extensionsManager = ExtensionsManager.getInstanceAsync(context, cameraProvider).await()
  val extensionsControl = extensionsManager.getCameraExtensionsControl(camera.cameraControl)
  extensionsControl?.setExtensionStrength(strength)
  

• Capture progress : Show a UI progress bar for long exposures.

  // Use the suspend extension function for takePicture to avoid callback boilerplate
  try {
      val result = imageCapture.takePicture(outputOptions)
      // Use result.savedUri or other fields
  } catch (e: ImageCaptureException) {
      // Handle capture failure
  }
  

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Low-light boost

LLB is designed for preview and video streams where you prefer high frame rates.

AE mode

The built-in CameraX way to prioritize brightness. It modifies the hardware's auto-exposure algorithm.

• Activation : Use CameraControl.enableLowLightBoostAsync.

• Implementation :

  // Enable Low Light Boost (LLB) natively in CameraX 1.4+
  camera.cameraControl.enableLowLightBoostAsync(true)
  

• Monitoring : Observe CameraInfo.lowLightBoostState to track when the hardware actively applies the enhancement.

Google Play services LLB

It's a multi-step implementation that uses a session-based SurfaceProcessor.

Dependency : com.google.android.gms:play-services-camera-low-light-boost

To implement Google Play services LLB, follow these core steps:

1. Initialize client : val client = LowLightBoost.getClient.

2. Implement SurfaceProcessor :

   • Manage session : Call client.createSession.
   • Forward required metadata : Observe the camera's TotalCaptureResult stream and forward every result to the session: session.processCaptureResult.
   • Provide surface : Get the input surface from the session, session.getCameraSurface, and provide it to the camera's SurfaceRequest.
   • Lifecycle : Release the session, session.release, when the processor is closed or the SurfaceRequest completes.

3. Wire using CameraEffect :

   val effect = SimpleCameraEffect(
       CameraEffect.PREVIEW or CameraEffect.VIDEO_CAPTURE,
       executor,
       llbSurfaceProcessor
   ) { throw it }
   
   // Add to UseCaseGroup
   val useCaseGroup = UseCaseGroup.Builder()
       .addUseCase(preview)
       .addUseCase(videoCapture)
       .addEffect(effect)
       .build()
   

4. Scene detection : Use session.setSceneDetectorCallback to receive boostStrength updates for real-time UI indicators.

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Implementation notes

• Thread safety : Always handle ExtensionsManager and LowLightBoostClient initialization asynchronously.
• FPS trade-offs: AE mode LLB often drops the frame rate significantly to increase brightness.
• Compatibility : Extensions, Night Mode, possibly conflict with ConcurrentCamera. Always verify support before binding.