Question

我正在开发一款需要使用固定（手动）对焦的Android相机应用，并始终使用闪光灯。我有一些似乎与闪光时间有关的问题。闪光灯始终闪光并始终获取图像，但有时闪光灯实际上并未照亮捕捉的画面。有些画面有闪光灯，有些画面过度曝光，有些画面暗;基本上它是不一致和不可预测的。

我的代码基于Camera2Basic示例。我想我已经在这里展示了所有相关部分：

我的预览请求构建器具有以下设置

mPreviewRequestBuilder.set(CaptureRequest.CONTROL_AF_MODE, CaptureRequest.CONTROL_AF_MODE_OFF);
float minimumLens = mCameraCharacteristics.get(CameraCharacteristics.LENS_INFO_MINIMUM_FOCUS_DISTANCE);
mPreviewRequestBuilder.set(CaptureRequest.LENS_FOCUS_DISTANCE, minimumLens);
mPreviewRequestBuilder.set(CaptureRequest.CONTROL_AWB_MODE,CaptureRequest.CONTROL_AWB_MODE_OFF);
mPreviewRequestBuilder.set(CaptureRequest.CONTROL_AE_MODE,CaptureRequest.CONTROL_AE_MODE_ON_ALWAYS_FLASH);
mPreviewRequestBuilder.set(CaptureRequest.FLASH_MODE, CameraMetadata.FLASH_MODE_OFF);

然后获取图片的实际序列（几乎直接来自Camera2Basic）是：

private void takePicture() {
    runPrecaptureSequence();
}

private CameraCaptureSession.CaptureCallback mCaptureCallback = new CameraCaptureSession.CaptureCallback() {

    private void process(CaptureResult result) {
        switch (mState) {
            case STATE_PREVIEW: {
                break;
            }
            case STATE_WAITING_PRECAPTURE: {
                Integer aeState = result.get(CaptureResult.CONTROL_AE_STATE);
                if (aeState == null ||
                        aeState == CaptureResult.CONTROL_AE_STATE_PRECAPTURE ||
                        aeState == CaptureRequest.CONTROL_AE_STATE_FLASH_REQUIRED) {
                    mState = STATE_CAPTURE;
                }
                break;
            }

            case STATE_CAPTURE: {
                // CONTROL_AE_STATE can be null on some devices
                Integer aeState = result.get(CaptureResult.CONTROL_AE_STATE);
                if (aeState == null || aeState != CaptureResult.CONTROL_AE_STATE_PRECAPTURE) {
                    mState = STATE_PICTURE_TAKEN;
                    captureStillPicture();
                }
                break;
            }
        }
    }

    @Override
    public void onCaptureProgressed(**ARGS**) {
        process(partialResult);
    }

    @Override
    public void onCaptureCompleted(**ARGS**) {
        process(result);
    }

};

private void runPrecaptureSequence() {
    try {          mPreviewRequestBuilder.set(CaptureRequest.CONTROL_AE_PRECAPTURE_TRIGGER, CaptureRequest.CONTROL_AE_PRECAPTURE_TRIGGER_START);
        mState = STATE_WAITING_PRECAPTURE;
        mCaptureSession.capture(mPreviewRequestBuilder.build(), mCaptureCallback, mBackgroundHandler);
    } catch (CameraAccessException e) {
        e.printStackTrace();
    }
}

private void captureStillPicture() {
    try {
        final Activity activity = getActivity();
        if (null == activity || null == mCameraDevice) {
            return;
        }

        final CaptureRequest.Builder captureBuilder = mCameraDevice.createCaptureRequest(CameraDevice.TEMPLATE_STILL_CAPTURE);
        captureBuilder.addTarget(mImageReader.getSurface());
        captureBuilder.set(CaptureRequest.CONTROL_AF_MODE, CaptureRequest.CONTROL_AF_MODE_OFF);           CaptureBuilder.set(CaptureRequest.CONTROL_AWB_MODE,CaptureRequest.CONTROL_AWB_MODE_OFF);
        float minimumLens = mCameraCharacteristics.get(CameraCharacteristics.LENS_INFO_MINIMUM_FOCUS_DISTANCE);
        captureBuilder.set(CaptureRequest.LENS_FOCUS_DISTANCE, minimumLens);
        captureBuilder.set(CaptureRequest.CONTROL_AE_MODE,CaptureRequest.CONTROL_AE_MODE_ON_ALWAYS_FLASH);
        captureBuilder.set(CaptureRequest.FLASH_MODE, CameraMetadata.FLASH_MODE_OFF);
        int rotation = activity.getWindowManager().getDefaultDisplay().getRotation();
        captureBuilder.set(CaptureRequest.JPEG_ORIENTATION, getOrientation(rotation));

        mFileName = getFileNameFromTime() + ".jpg";

        CameraCaptureSession.CaptureCallback CaptureCallback
                = new CameraCaptureSession.CaptureCallback() {

            @Override
            public void onCaptureCompleted(@NonNull CameraCaptureSession session,
                                           @NonNull CaptureRequest request,
                                           @NonNull TotalCaptureResult result) {
                resumePreview();
            }
        };

        mCaptureSession.stopRepeating();
        mCaptureSession.capture(captureBuilder.build(), CaptureCallback, null);
    } catch (CameraAccessException e) {
        e.printStackTrace();
    }
}

保存图像发生在ImageReader onImageAvailableListener调用中并且工作正常。

看起来闪存在获取图像之前就已经开始了，所以我尝试了this answer中的建议，但FLASH_FIRED条件建议从未触发过。

任何比我熟悉Camera2的人都能看到我搞砸了吗？

Answer 1

我已经看到了camera2basic https://github.com/googlearchive/android-Camera2Basic的代码及其较新的Java版本https://github.com/android/camera-samples/tree/master/Camera2BasicJava

因此，在代码中，基本上有3个地方设置了Flash（我正在谈论较新的Java版本）

1）私有void createCameraPreviewSession（）函数

2）私有void captureStillPicture（）

3）私有无效的unlockFocus（）

1）将要显示预览时调用createCameraPreviewSession（）函数（因此，我想从应用程序的开头开始Flash并相应地调用这些函数）

2）当捕获高清图片时，将调用captureStillPicture（）函数

3）捕获图像并在单击高清图片时要解锁焦点时，将调用unlockFocus（）函数

因此，如果闪光灯闪烁或图像被冲洗掉，则可能仅在后两个功能之一中设置了闪光灯模式手电筒在最后两个功能中设置合适的闪光模式，并尝试避免刚开始闪光后捕获的第一帧我正在像这样设置闪光灯

       int flashFlag=1;
private void setAutoFlash(CaptureRequest.Builder requestBuilder) {
    if (mFlashSupported) {


        if (flashFlag==1)
        {
            requestBuilder.set(CaptureRequest.CONTROL_AE_MODE,CaptureRequest.CONTROL_AE_MODE_ON);
            requestBuilder.set(CaptureRequest.FLASH_MODE,CaptureRequest.FLASH_MODE_TORCH);
        }
        else
        {
            requestBuilder.set(CaptureRequest.CONTROL_AE_MODE,
                CaptureRequest.CONTROL_AE_MODE_ON);
        }


    }
}

i使flashFlag成为全局变量并将其设置在两个位置，并拒绝第一个Flash HD帧，因为它通常会被冲洗掉

也不要在未捕获高清图片的情况下尝试打开闪光灯，因为它会锁定您的对焦

Answer 2

将以下三行添加到Camera2Basic Sample：

mPreviewRequestBuilder.set(CaptureRequest.CONTROL_MODE, CaptureRequest.CONTROL_MODE_OFF);
mPreviewRequestBuilder.set(CaptureRequest.SENSOR_SENSITIVITY, 4000);
mPreviewRequestBuilder.set(CaptureRequest.FLASH_MODE, FLASH_MODE_TORCH);

当激活Flash并启动repeatingRequest时，某些默认设置（传感器灵敏度：100）会覆盖手动设置。但该请求明确指出传感器灵敏度应为4000。我在onCaptureCompleted方法中用这两行测试了它：

Log.d(TAG, "request: "+request.get(CaptureRequest.SENSOR_SENSITIVITY));
Log.d(TAG, "result: "+result.get(CaptureResult.SENSOR_SENSITIVITY));

Android Camera2 Flash时序问题

2 个答案: