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弱光增强

Android 15 引入了低光增强功能，这是一种新的自动曝光模式，相机 2 和夜间模式相机扩展程序。弱光增强在光线较暗时自动调整预览视频流的亮度条件。这与夜间模式相机扩展程序创建的方式不同因为夜间模式会合并多张连拍照片美化图片。虽然夜间模式对于制作静态图片非常有效，无法创建连续的帧流，但“低光增强”功能可以。因此， “低光增强”可启用新的相机功能，例如：

提供增强的图片预览，以便用户能够更好地设定图片预览效果，低光照下的照片。
在光线昏暗的环境下扫描二维码。

如果您启用“弱光增强”功能，系统会在光线较暗时自动开启该功能并在光线充足时关闭。

应用可在光线较暗的情况下从预览视频流中录制下来，以保存调亮的视频。

您可以在 Camera2 中或通过相机扩展程序。本文档介绍了如何将“弱光增强”与 Camera2 搭配使用。您还可以使用使用夜间模式相机扩展进行弱光增强（如果受设备。

检查可用性

在使用“弱光增强”功能之前，请确保设备支持该功能。如果 “低光增强”是 camera2.CameraCharacteristics.CONTROL_AE_AVAILABLE_MODES。（弱光模式）与其他自动曝光设置一样，“增强”是其自身的自动曝光设置与“低光增强”执行的预览提亮功能不兼容。）

因此，如要检查“低光增强”功能是否可用，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

要在 Camera2 会话中启用“弱光增强”，请将设置 CaptureRequest.CONTROL_AE_MODE至 ON_LOW_LIGHT_BOOST_BRIGHTNESS_PRIORITY。之后，您需要确认“低光增强”已开启；为此，您可以查看 CaptureResult.CONTROL_AE_MODE 字段。你需要进行检查，因为光线较暗 “增强”功能并非与所有相机配置都兼容。例如，高速出于 FPS 的考虑，录制不支持低光增强。如果 “弱光增强”未开启，你可能需要更换摄像头然后重试。

Kotlin

val captureRequestBuilder = camera.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

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) ==
          CameraMetadata.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
);

监控弱光增强

“低光增强”可在弱光条件下使预览视频流变亮；如果环境已经足够亮，可以达到正常亮度，则不会产生任何效果捕获。您可以通过查看 CaptureResult.CONTROL_LOW_LIGHT_BOOST_STATE 字段。如果您 “弱光增强”已开启，且当前处于启用状态，该字段会设为 CameraMetadata.CONTROL_LOW_LIGHT_BOOST_STATE_ACTIVE。然后，您可以向月亮图标或指示预览变亮的其他指示。

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) ==
        CameraMetadata.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) ==
        CameraMetadata.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
);