Question

我尝试使用Galaxy S4上的Camera2 API捕获图像数据。 ImageReader被用作表面提供者。已使用ImageFormat.YV12和ImageFormat.YUV_420_888尝试使用的图像格式，并生成相同的结果。

设置似乎很好，我使用ImageReader从ImageReader获取一个Image。图像有3个平面。缓冲区是预期的大小，Y平面的宽度*高度和其他两个平面的（宽度*高度）/ 4。

问题在于我没有以两种方式正确获取数据。第一个问题是Y平面数据是镜像。这可以处理，虽然很奇怪所以我很好奇，如果这是预期的。

更糟糕的问题是，其他两架飞机似乎根本无法正确传送数据。例如，如果图像大小为640x480，导致U和V缓冲区大小为76800字节，则只有缓冲区的前320字节为非零值。这个数字有所不同，似乎不符合不同图像尺寸之间的设定比例，但在每种尺寸的图像之间似乎都是一致的。

我想知道在使用此API时是否存在我遗漏的内容。代码如下。

public class OnboardCamera {
  private final String TAG = "OnboardCamera";

  int mWidth = 1280;
  int mHeight = 720;
  int mYSize = mWidth*mHeight;
  int mUVSize = mYSize/4;
  int mFrameSize = mYSize+(mUVSize*2); 

  //handler for the camera
  private HandlerThread mCameraHandlerThread;
  private Handler mCameraHandler;

  //the size of the ImageReader determines the output from the camera.
  private ImageReader mImageReader = ImageReader.newInstance(mWidth, mHeight, ImageFormat.YV12, 30);

  private Surface mCameraRecieverSurface = mImageReader.getSurface();
  {
      mImageReader.setOnImageAvailableListener(mImageAvailListener, mCameraHandler);
  }

  private byte[] tempYbuffer = new byte[mYSize];
  private byte[] tempUbuffer = new byte[mUVSize];
  private byte[] tempVbuffer = new byte[mUVSize];

  ImageReader.OnImageAvailableListener mImageAvailListener = new ImageReader.OnImageAvailableListener() {
      @Override
      public void onImageAvailable(ImageReader reader) {
          //when a buffer is available from the camera
          //get the image
          Image image = reader.acquireNextImage();
          Image.Plane[] planes = image.getPlanes();

          //copy it into a byte[]
          byte[] outFrame = new byte[mFrameSize];
          int outFrameNextIndex = 0;


          ByteBuffer sourceBuffer = planes[0].getBuffer();
          sourceBuffer.get(tempYbuffer, 0, tempYbuffer.length);

          ByteBuffer vByteBuf = planes[1].getBuffer();
          vByteBuf.get(tempVbuffer);

          ByteBuffer yByteBuf = planes[2].getBuffer();
          yByteBuf.get(tempUbuffer);

          //free the Image
          image.close();
      }
  };


  OnboardCamera() {
      mCameraHandlerThread = new HandlerThread("mCameraHandlerThread");
      mCameraHandlerThread.start();
      mCameraHandler = new Handler(mCameraHandlerThread.getLooper());

  }




  @Override
  public boolean startProducing() {
      CameraManager cm = (CameraManager) Ten8Application.getAppContext().getSystemService(Context.CAMERA_SERVICE);
      try {
          String[] cameraList = cm.getCameraIdList();
          for (String cd: cameraList) {
              //get camera characteristics
              CameraCharacteristics mCameraCharacteristics = cm.getCameraCharacteristics(cd);

              //check if the camera is in the back - if not, continue to next
              if (mCameraCharacteristics.get(CameraCharacteristics.LENS_FACING) != CameraCharacteristics.LENS_FACING_BACK) {
                  continue;
              }

              //get StreamConfigurationMap - supported image formats
              StreamConfigurationMap scm = mCameraCharacteristics.get(CameraCharacteristics.SCALER_STREAM_CONFIGURATION_MAP);

              android.util.Size[] sizes =  scm.getOutputSizes(ImageFormat.YV12);

              cm.openCamera(cd, mDeviceStateCallback, mCameraHandler);
          }

      } catch (CameraAccessException e) {
          e.printStackTrace();
          Log.e(TAG, "CameraAccessException detected", e);
      }
      return false;
  }

  private final CameraDevice.StateCallback mDeviceStateCallback = new CameraDevice.StateCallback() {
      @Override
      public void onOpened(CameraDevice camera) {
          //make list of surfaces to give to camera
          List<Surface> surfaceList = new ArrayList<>();
          surfaceList.add(mCameraRecieverSurface);

          try {
              camera.createCaptureSession(surfaceList, mCaptureSessionStateCallback, mCameraHandler); 
          } catch (CameraAccessException e) {
              Log.e(TAG, "createCaptureSession threw CameraAccessException.", e);
          }
      }

      @Override
      public void onDisconnected(CameraDevice camera) {

      }

      @Override
      public void onError(CameraDevice camera, int error) {

      }
  };

  private final CameraCaptureSession.StateCallback mCaptureSessionStateCallback = new CameraCaptureSession.StateCallback() {
      @Override
      public void onConfigured(CameraCaptureSession session) {
          try {
              CaptureRequest.Builder requestBuilder = session.getDevice().createCaptureRequest(CameraDevice.TEMPLATE_RECORD);
              requestBuilder.addTarget(mCameraRecieverSurface);
              //set to null - image data will be produced but will not receive metadata
              session.setRepeatingRequest(requestBuilder.build(), null, mCameraHandler); 

          } catch (CameraAccessException e) {
              Log.e(TAG, "createCaptureSession threw CameraAccessException.", e);
          }


      }

      @Override
      public void onConfigureFailed(CameraCaptureSession session) {

      }
  };
}

Answer 1

您是否关注Image.Plane的row-和pixelStride参数？

由于硬件内存映射约束，行步幅通常大于图像的宽度，图像中行y的开始位于（y rowStride）而不是（y （）宽度）在给定平面的ByteArray中。

如果是这种情况，那么对于640x480图像（1行二次采样色度数据）的前320个字节后，U或V平面在一段时间内将为0并不奇怪 - 应该有（rowStride - width）字节为零或垃圾，然后下一行像素数据将开始。

请注意，如果pixelStride不是1，那么您还必须跳过像素值之间的字节;当底层YCbCr缓冲区实际上是半平面而非平面时，最常使用这种方法。

Answer 2

我遇到了同样的问题，我认为这个问题出现在Android API 21中。我升级到API 23并且相同的代码运行正常。也在API 22上进行了测试，它也有效。

将Camera2 API与ImageReader一起使用

2 个答案: