Camera2中的前置摄像头未捕获图像

Question

我有来自https://github.com/googlesamples/android-Camera2Basic 的 Camera2 的代码。

我面临的问题是，当我打开前置摄像头时，我无法拍摄照片，但使用后置摄像头可以正常工作。

有人实现了Camera2 Api吗，请帮忙！

这里是sn-p的代码：

private void setUpCameraOutputs(int width, int height) {
    Activity activity = getActivity();
    CameraManager manager = (CameraManager) activity.getSystemService(Context.CAMERA_SERVICE);
    try {
        for (String cameraId : manager.getCameraIdList()) {
            CameraCharacteristics characteristics
                    = manager.getCameraCharacteristics(cameraId);

            // We don't use a front facing camera in this sample.
            int facing = characteristics.get(CameraCharacteristics.LENS_FACING);
            Log.i(TAG,"Front Cam ID: "+ facing);
            if (characteristics.get(CameraCharacteristics.LENS_FACING)==CameraCharacteristics.LENS_FACING_FRONT)
            {



                StreamConfigurationMap map = characteristics.get(
                        CameraCharacteristics.SCALER_STREAM_CONFIGURATION_MAP);


                // For still image captures, we use the largest available size.
                Size largest = Collections.max(
                        Arrays.asList(map.getOutputSizes(ImageFormat.JPEG)),
                        new CompareSizesByArea());
                mImageReader = ImageReader.newInstance(largest.getWidth(), largest.getHeight(),
                        ImageFormat.JPEG, /*maxImages*/2);
                mImageReader.setOnImageAvailableListener(
                        mOnImageAvailableListener, mBackgroundHandler);

                // Danger, W.R.! Attempting to use too large a preview size could  exceed the camera
                // bus' bandwidth limitation, resulting in gorgeous previews but the storage of
                // garbage capture data.
                mPreviewSize = chooseOptimalSize(map.getOutputSizes(SurfaceTexture.class),
                        width, height, largest);

                // We fit the aspect ratio of TextureView to the size of preview we picked.
                int orientation = getResources().getConfiguration().orientation;
                if (orientation == Configuration.ORIENTATION_LANDSCAPE) {
                    mTextureView.setAspectRatio(
                            mPreviewSize.getWidth(), mPreviewSize.getHeight());
                } else {
                    mTextureView.setAspectRatio(
                            mPreviewSize.getHeight(), mPreviewSize.getWidth());
                }

                mCameraId = cameraId;
                return;
            }
            else
            {
                onActivityCreated(Bundle.EMPTY);
            }
        }
    } catch (CameraAccessException e) {
        e.printStackTrace();
    } catch (NullPointerException e) {
        // Currently an NPE is thrown when the Camera2API is used but not supported on the
        // device this code runs.
        ErrorDialog.newInstance(getString(R.string.camera_error))
                .show(getChildFragmentManager(), FRAGMENT_DIALOG);
    }
}

Answer 1

问题在于许多前置摄像头都有固定焦距。因此，在lockFocus() 中的自动对焦触发后，自动对焦状态 (CONTROL_AF_STATE) 保持 INACTIVE 并且自动对焦触发器什么也不做。

因此，为了使其正常工作，您需要检查是否支持自动对焦。为此，请将以下内容添加到setUpCameraOutputs()：

int[] afAvailableModes = characteristics.get(CameraCharacteristics.CONTROL_AF_AVAILABLE_MODES);

if (afAvailableModes.length == 0 || (afAvailableModes.length == 1
        && afAvailableModes[0] == CameraMetadata.CONTROL_AF_MODE_OFF)) {
    mAutoFocusSupported = false;
} else {
    mAutoFocusSupported = true;
}

最后，如果你想拍照的时候不支持，就不要锁定焦点：

private void takePicture() {
    if (mAutoFocusSupported) {
        lockFocus();
    } else {
        captureStillPicture();
    }
}

Answer 2

对于 Camera2 Api，Google 的视频示例适用于前置和后置摄像头，但对于图像捕获，Google 的示例仅适用于后置摄像头，不适用于前置摄像头。
适合我的解决方案是

在lockFocus()方法中，替换行

mCaptureSession.capture(mPreviewRequestBuilder.build(),
                                                  mCaptureCallback, mBackgroundHandler);

与

captureStillPicture();

希望这会有所帮助！

Answer 3

@ArvindSingh 的解决方案不是最好的，因为您还会禁用后置摄像头的对焦功能。更好的解决方案是像这样在 takePicture 中进行摄像头朝向检查：

private void takePicture() {
    if (CameraCharacteristics.LENS_FACING_FRONT == mSelectedFacing) {
        // front camera selected, so take a picture without focus
        captureStillPicture();
    } else {
        // back camera selected, trigger the focus before creating an image
        lockFocus();
    }
}

对于此解决方案，您只需将当前使用的朝向保存在 mSelectedFacing 中的某处即可

Answer 4

在lockFocus()方法中，替换行

mCaptureSession.capture(mPreviewRequestBuilder.build(),
                                              mCaptureCallback,    mBackgroundHandler);

与

captureStillPicture();

为了防止不需要的方向，您可以使用

/** * 从屏幕旋转到 JPEG 方向的转换。 */

   static {
       ORIENTATIONS.append(Surface.ROTATION_0, 270);
       ORIENTATIONS.append(Surface.ROTATION_90, 0);
       ORIENTATIONS.append(Surface.ROTATION_180, 180);
       ORIENTATIONS.append(Surface.ROTATION_270, 270);
   }

Answer 5

请尝试使用此代码进行捕获

case STATE_WAITING_LOCK: {
                Integer afState = result.get(CaptureResult.CONTROL_AF_STATE);
                if (afState == null) {
                    captureStillPicture();
                } else if (CaptureResult.CONTROL_AF_STATE_FOCUSED_LOCKED == afState ||
                        CaptureResult.CONTROL_AF_STATE_NOT_FOCUSED_LOCKED == afState ||
                         CaptureResult.CONTROL_AF_STATE_INACTIVE == afState /*add this*/) {
                    // 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_CONVERGED) {
                        mState = STATE_PICTURE_TAKEN;
                        captureStillPicture();
                    } else {
                        runPrecaptureSequence();
                    }
                }
                break;
            }