弱光增强

Android 15 引入了低光增强，这是一种新的自动曝光模式，可供 Camera 2 和夜间模式相机扩展使用。“低光提升”功能会在弱光条件下自动调整预览数据流的亮度。这与夜间模式相机扩展程序创建静态图片的方式不同，因为夜间模式会合并多张照片来制作单张增强图片。虽然夜间模式非常适合创建静态图片，但无法创建连续的帧流，但“低光增强”可以。因此，“低光增强”可以启用新的相机功能，例如：

  • 提供增强的图片预览，以便用户能够更好地针对弱光环境取景。
  • 在光线昏暗的环境下扫描二维码。

如果您启用“弱光增强”，它会在光线较暗时自动开启，在光线较暗时关闭。

应用可以在光线昏暗的环境下录制预览流，以保存明亮的视频。

您可以在 Camera2 中或通过相机扩展使用弱光提升。本文档介绍了如何搭配使用“弱光增强”与 Camera2。如果设备支持，您还可以将“低光增强”与夜间模式相机扩展搭配使用。

检查是否有空房

在使用弱光增强之前，请检查设备是否支持该模式。如果有可用，“低光增强”是 camera2.CameraCharacteristics.CONTROL_AE_AVAILABLE_MODES 中列出的曝光模式之一。（低光增强是自身的自动曝光设置，因为其他自动曝光设置与低光增强执行的预览亮度不兼容。）

因此，如需检查是否可使用“弱光增强”，请调用 CameraCharacteristics.get(CameraCharacteristics.CONTROL_AE_AVAILABLE_MODES) 并检查返回的模式是否包含 ON_LOW_LIGHT_BOOST_BRIGHTNESS_PRIORITY：

Kotlin

val characteristics = cameraManager.getCameraCharacteristics(cameraId)
val autoExposureModes =
    characteristics.get(CameraCharacteristics.CONTROL_AE_AVAILABLE_MODES)!!
val lowLightBoostSupported = autoExposureModes.contains(
        CameraMetadata.CONTROL_AE_MODE_ON_LOW_LIGHT_BOOST_BRIGHTNESS_PRIORITY)

if (lowLightBoostSupported) {
  // Enable Low Light Boost (next section)
} else {
  // Proceed without Low Light Boost
}

Java

CameraCharacteristics characteristics =
    mCameraManager.getCameraCharacteristics(cameraId);
int[] autoExposureModes =
    characteristics.get(CameraCharacteristics.CONTROL_AE_AVAILABLE_MODES);
boolean lowLightBoostSupported = autoExposureModes.contains(
        CameraMetadata.CONTROL_AE_MODE_ON_LOW_LIGHT_BOOST_BRIGHTNESS_PRIORITY);

if (lowLightBoostSupported) {
  // Enable Low Light Boost (next section)
} else {
  // Proceed without Low Light Boost
}

启用弱光增强

如需在 Camera2 会话中启用弱光提升，请将 CaptureRequest.CONTROL_AE_MODE 设置为 ON_LOW_LIGHT_BOOST_BRIGHTNESS_PRIORITY。之后，您需要确认“弱光增强”已开启；您可以通过查看 CaptureResult.CONTROL_AE_MODE 字段执行此操作。您需要进行检查，因为“弱光提升”功能并不与所有相机配置都兼容。例如，出于 FPS 方面的考虑，高速录制不支持低光提升。如果“低光提升”功能未开启，您可能需要更改摄像头配置，然后重试。

Kotlin

val captureRequestBuilder = camera.createCaptureRequest(
  CameraDevice.TEMPLATE_PREVIEW)
if (isLowLightBoostAvailable(cameraId)) {
  captureRequestBuilder.set(
    CaptureRequest.CONTROL_AE_MODE,
    CaptureMetadata.CONTROL_AE_MODE_ON_LOW_LIGHT_BOOST_BRIGHTNESS_PRIORITY
  )
}
// other capture request params

session.setRepeatingRequest(
  captureRequestBuilder.build(),
  object : CaptureCallback() {
    @Override
    fun onCaptureCompleted(session: CameraCaptureSession,
        request: CaptureRequest, result: TotalCaptureResult) {
      // verify Low Light Boost AE mode set successfully
      result.get(CaptureResult.CONTROL_AE_MODE) ==
          CaptureMetadata.CONTROL_AE_MODE_ON_LOW_LIGHT_BOOST_BRIGHTNESS_PRIORITY
    }
  },
  cameraHandler
)

Java

CaptureRequest.Builder captureRequestBuilder =
  mCamera.createCaptureRequest(CameraDevice.TEMPLATE_PREVIEW);
if (isLowLightBoostAvailable(cameraId)) {
  captureRequestBuilder.set(
    CaptureRequest.CONTROL_AE_MODE,
    CameraMetadata.CONTROL_AE_MODE_ON_LOW_LIGHT_BOOST_BRIGHTNESS_PRIORITY);
}
// other capture request params

mSession.setRepeatingRequest(
  captureRequestBuilder.build(),
  new CaptureCallback() {
    @Override
    public void onCaptureCompleted(CameraCaptureSession session,
        CaptureRequest request, TotalCaptureResult result) {
      // verify Low Light Boost AE mode set successfully
      result.get(CaptureResult.CONTROL_AE_MODE) ==
          CameraMetadata.CONTROL_AE_MODE_ON_LOW_LIGHT_BOOST_BRIGHTNESS_PRIORITY;
    }
  },
  mCameraHandler
);

显示器弱光增强

“低光增强”功能会在弱光条件下使预览视频流变亮，并且如果环境亮度足以进行正常拍摄，则不会产生任何效果。您可以通过查看 CaptureResult.CONTROL_LOW_LIGHT_BOOST_STATE 字段来确认“弱光增强”当前是否处于启用状态。如果您已开启“低光增强”功能，并且它当前处于活跃状态，则该字段设置为 CameraMetadata.CONTROL_LOW_LIGHT_BOOST_STATE_ACTIVE。然后，可能会显示月亮图标或其他一些指示，表明预览正在变亮。

Kotlin

session.setRepeatingRequest(
  captureRequestBuilder.build(),
  object : CaptureCallback() {
    @Override
    fun onCaptureCompleted(session: CameraCaptureSession,
        request: CaptureRequest, result: TotalCaptureResult) {
      // check if Low Light Boost is active or inactive
      if (result.get(CaptureResult.CONTROL_LOW_LIGHT_BOOST_STATE) ==
        CaptureMetadata.CONTROL_LOW_LIGHT_BOOST_STATE_ACTIVE) {
        // Low Light Boost state is active
        // Show Moon Icon
      } else {
        // Low Light Boost state is inactive or AE mode is not set
        // to Low Light Boost
        // Hide Moon Icon
      }
    }
  },
  cameraHandler
)

Java

mSession.setRepeatingRequest(
  captureRequestBuilder.build(),
  new CaptureCallback() {
    @Override
    public void onCaptureCompleted(CameraCaptureSession session,
        CaptureRequest request, TotalCaptureResult result) {
      // check if Low Light Boost is active or inactive
      if (result.get(CaptureResult.CONTROL_LOW_LIGHT_BOOST_STATE) ==
        CaptureMetadata.CONTROL_LOW_LIGHT_BOOST_STATE_ACTIVE) {
        // Low Light Boost state is active
        // Show Moon Icon
      } else {
        // Low Light Boost state is inactive or AE mode is not set
        // to Low Light Boost
        // Hide Moon Icon
      }
    }
  },
  mCameraHandler
);