说明：转载自 Android Camera，不定期添加自己的学习思考。
Monochrome Cameras
Devices running Android 9 or higher can support monochrome cameras. Android 10 provides additional support for the Y8 stream format, monochrome and near-infrared (NIR) color filter array static metadata, and DngCreator functions for monochrome cameras.
With this capability, device manufacturers can implement a monochrome or NIR camera device and reduce memory use by using the Y8 stream format. A monochrome camera can serve as the underlying physical camera of a logical multi-camera device to achieve better low-light noise characteristics.
Implementation
Hardware requirements
To implement this feature, your device must have a monochrome camera sensor and an image signal processor (ISP) to process the sensor output.
Implementing a monochrome camera
To advertise a camera device as a monochrome camera, the Camera HAL must meet the following requirements:
android.sensor.info.colorFilterArray is set to MONO or NIR.
BACKWARD_COMPATIBLE required keys are supported and MANUAL_POST_PROCESSING isn’t supported.
android.control.awbAvailableModes only contains AUTO and android.control.awbState is either CONVERTED or LOCKED depending on android.control.awbLock.
android.colorCorrection.mode, android.colorCorrection.transform, and android.colorCorrection.gains aren’t in available request and result keys. As a result, the camera device is LIMITED.
The following color-related static metadata keys aren’t present:
android.sensor.referenceIlluminant*
android.sensor.calibrationTransform*
android.sensor.colorTransform*
android.sensor.forwardMatrix*
android.sensor.neutralColorPoint
android.sensor.greenSplit
All color channels have the same values for the following metadata keys:
android.sensor.blackLevelPattern
android.sensor.dynamicBlackLevel
android.statistics.lensShadingMap
android.tonemap.curve
android.sensor.noiseProfile has only one color channel.
For monochrome devices supporting Y8 stream formats, the Camera HAL must support swapping YUV_420_888 formats in mandatory stream combinations (including reprocessing) with Y8 formats.
The following public APIs are used in this feature:
Y8 image format
SENSOR_INFO_COLOR_FILTER_ARRANGEMENT_MONO
SENSOR_INFO_COLOR_FILTER_ARRANGEMENT_NIR
MONOCHROME camera capability (introduced in Android 9)
For more details on the Camera HAL, see docs.html. For more information on related public APIs, see ImageFormat, CameraCharacteristics, CaptureRequest, and CaptureResult.
Validation
To validate your implementation of a monochrome camera, run the following CTS and VTS tests.
CTS tests
testMonochromeCharacteristics
CaptureRequestTest
CaptureResultTest
StillCaptureTest
DngCreatorTest
VTS tests
getCameraCharacteristics
processMultiCaptureRequestPreview
