Camera2 - 设置AE区域、AF区域和AWB区域的问题。

Question

我对camera2还不熟悉，目前已经在Camera2中实现了大部分功能，但我的要求是焦点应该在中间，曝光和白平衡应该基于中间部分进行计算。

为了计算中间区域，我使用了以下方法。

fun getRegion() : MeteringRectangle {
    val sensorRect: Rect = characteristics.get(CameraCharacteristics.SENSOR_INFO_ACTIVE_ARRAY_SIZE)!!
    val sensorOrientation = characteristics.get(CameraCharacteristics.SENSOR_ORIENTATION)!!

    val regionWidth = 200
    val regionHeight = 200
    var regionLeft: Int = (sensorRect.width() - regionWidth) / 2
    var regionTop: Int = (sensorRect.height() - regionHeight) / 2

    if (sensorOrientation == 90 || sensorOrientation == 270) {
        val temp = regionLeft
        regionLeft = regionTop
        regionTop = temp
    }

    return MeteringRectangle(
        regionLeft,
        regionTop,
        regionWidth,
        regionHeight,
        MeteringRectangle.METERING_WEIGHT_MAX - 1
    )
}

我觉得这个结果很有希望，但由于我是初学者，我真的无法完全理解这个API的整个过程。我尝试像这样设置区域，但没有取得积极的结果，预览图像变得模糊不清。

private fun createPreviewRequest() {
    val previewSurface = Surface(viewFinder.surfaceTexture)

    repeatingRequest = cameraDevice.createCaptureRequest(CameraDevice.TEMPLATE_PREVIEW)
    repeatingRequest.addTarget(previewSurface)
    val matArr = getRegion()

    repeatingRequest.apply {
        set(CaptureRequest.CONTROL_AWB_REGIONS, arrayOf(matArr))
        set(CaptureRequest.CONTROL_AF_REGIONS, arrayOf(matArr))
        set(CaptureRequest.CONTROL_AE_REGIONS, arrayOf(matArr))
        set(CaptureRequest.CONTROL_AWB_MODE, CaptureRequest.CONTROL_AWB_MODE_AUTO)
        set(CaptureRequest.CONTROL_AF_MODE, CaptureRequest.CONTROL_AF_MODE_AUTO)
        set(CaptureRequest.CONTROL_AE_MODE, CaptureRequest.CONTROL_AE_MODE_ON)
        set(CaptureRequest.FLASH_MODE, CaptureRequest.FLASH_MODE_TORCH)
    }

    cameraCaptureSession.setRepeatingRequest(repeatingRequest.build(), captureCallBack, cameraHandler)
}

实施我的需求可能需要什么流程？

注意：为了简单起见，我没有对设备是否支持AE、AF、AWB区域进行检查。

- kallis

Answer 1

使用Camera2 API：

• 您需要将自动对焦和自动曝光区域设置为用户点击的区域，可以使用 CONTROL_AF_REGIONS 和 CONTROL_AE_REGIONS 键来实现。这些单位需要从您的 UI 触摸坐标转换为传感器的活动阵列坐标。
  计算出区域后，您应该将 AF 模式设置为 AUTO，然后触发 AF 并等待 CONTROL_AF_STATE_FOCUSED_LOCKED 来拍摄一个清晰的照片。如果您想在一段时间后返回到正常操作状态，或者用户取消了触摸对焦操作，应将 AF 模式切换回 CONTROL_AF_MODE_CONTINUOUS_PICTURE。
  参见 "在 Camera2 API 中实现点击对焦"。

• 关于曝光控制，您可以通过使用 SENSOR_EXPOSURE_TIME 和 SENSOR_SENSITIVITY 键手动设置曝光时间和 ISO。例如，将曝光时间设置为 500000000L 将导致 0.5 秒的曝光时间，并将 SENSOR_SENSITIVITY 设置为 400 将导致 ISO 为 400。

举个当前（2023年）的例子，我建议你看一下{{link1：android/camera-samples/Camera2Extensions，类 java/com/example/android/camera2/extensions/fragments/CameraFragment.kt}}，它具有与焦点相关的功能。

例如：

/**
 * Translates a touch event relative to the preview surface to a region relative to the sensor.
 * Note: This operation does not account for zoom / crop and should be handled otherwise the touch
 * point won't correctly map to the sensor.
 */
private fun meteringRectangle(event: MotionEvent): MeteringRectangle {
val sensorOrientation = characteristics.get(CameraCharacteristics.SENSOR_ORIENTATION)!!
val sensorSize = characteristics.get(CameraCharacteristics.SENSOR_INFO_ACTIVE_ARRAY_SIZE)!!

val halfMeteringRectWidth = (METERING_RECTANGLE_SIZE * sensorSize.width()) / 2
val halfMeteringRectHeight = (METERING_RECTANGLE_SIZE * sensorSize.height()) / 2

// Normalize the [x,y] touch point in the view port to values in the range of [0,1]
val normalizedPoint = floatArrayOf(event.x / previewSize.height, event.y / previewSize.width)

// Scale and rotate the normalized point such that it maps to the sensor region
Matrix().apply {
    postRotate(-sensorOrientation.toFloat(), 0.5f, 0.5f)
    postScale(sensorSize.width().toFloat(), sensorSize.height().toFloat())
    mapPoints(normalizedPoint)
}

val meteringRegion = Rect(
    (normalizedPoint[0] - halfMeteringRectWidth).toInt().coerceIn(0, sensorSize.width()),
    (normalizedPoint[1] - halfMeteringRectHeight).toInt().coerceIn(0, sensorSize.height()),
    (normalizedPoint[0] + halfMeteringRectWidth).toInt().coerceIn(0, sensorSize.width()),
    (normalizedPoint[1] + halfMeteringRectHeight).toInt().coerceIn(0, sensorSize.height())
)

return MeteringRectangle(meteringRegion, MeteringRectangle.METERING_WEIGHT_MAX)
}

private fun startAutoFocus(meteringRectangle: MeteringRectangle) {
submitRequest(
    CameraDevice.TEMPLATE_PREVIEW,
    previewSurface,
    false,
    ) { request ->
        request.apply {
        set(CaptureRequest.CONTROL_AF_REGIONS, arrayOf(meteringRectangle))
        set(CaptureRequest.CONTROL_AF_MODE, CaptureRequest.CONTROL_AF_MODE_AUTO)
        set(CaptureRequest.CONTROL_AF_TRIGGER, CameraMetadata.CONTROL_AF_TRIGGER_START)
        setTag(AUTO_FOCUS_TAG)
        }
    }
}

- VonC