Question

我使用OnImageAvailableListener获取预览帧：

@Override
public void onImageAvailable(ImageReader reader) {
    Image image = null;
    try {
        image = reader.acquireLatestImage();
        Image.Plane[] planes = image.getPlanes();
        ByteBuffer buffer = planes[0].getBuffer();
        byte[] data = new byte[buffer.capacity()];
        buffer.get(data);
        //data.length=332803; width=3264; height=2448
        Log.e(TAG, "data.length=" + data.length + "; width=" + image.getWidth() + "; height=" + image.getHeight());
        //TODO data processing
    } catch (Exception e) {
        e.printStackTrace();
    }
    if (image != null) {
        image.close();
    }
}

每次数据长度不同但图像宽度和高度相同主要问题：data.length太小，无法达到3264x2448等分辨率数据阵列的大小应为3264 * 2448 = 7,990,272，而不是300,000 - 600,000 有什么问题？

imageReader = ImageReader.newInstance(3264, 2448, ImageFormat.JPEG, 5);

Answer 1

我通过使用 YUV_420_888 图片格式并手动将其转换为 JPEG 图片格式来解决此问题。

imageReader = ImageReader.newInstance(MAX_PREVIEW_WIDTH, MAX_PREVIEW_HEIGHT, 
                                      ImageFormat.YUV_420_888, 5);
imageReader.setOnImageAvailableListener(this, null);

Surface imageSurface = imageReader.getSurface();
List<Surface> surfaceList = new ArrayList<>();
//...add other surfaces
previewRequestBuilder = cameraDevice.createCaptureRequest(CameraDevice.TEMPLATE_PREVIEW);
previewRequestBuilder.addTarget(imageSurface);
            surfaceList.add(imageSurface);
cameraDevice.createCaptureSession(surfaceList,
                    new CameraCaptureSession.StateCallback() {
//...implement onConfigured, onConfigureFailed for StateCallback
}, null);

@Override
public void onImageAvailable(ImageReader reader) {
    Image image = reader.acquireLatestImage();
    if (image != null) {
        //converting to JPEG
        byte[] jpegData = ImageUtils.imageToByteArray(image);
        //write to file (for example ..some_path/frame.jpg)
        FileManager.writeFrame(FILE_NAME, jpegData);
        image.close();
    }
}

public final class ImageUtil {

    public static byte[] imageToByteArray(Image image) {
        byte[] data = null;
        if (image.getFormat() == ImageFormat.JPEG) {
            Image.Plane[] planes = image.getPlanes();
            ByteBuffer buffer = planes[0].getBuffer();
            data = new byte[buffer.capacity()];
            buffer.get(data);
            return data;
        } else if (image.getFormat() == ImageFormat.YUV_420_888) {
            data = NV21toJPEG(
                    YUV_420_888toNV21(image),
                    image.getWidth(), image.getHeight());
        }
        return data;
    }

    private static byte[] YUV_420_888toNV21(Image image) {
        byte[] nv21;
        ByteBuffer yBuffer = image.getPlanes()[0].getBuffer();
        ByteBuffer uBuffer = image.getPlanes()[1].getBuffer();
        ByteBuffer vBuffer = image.getPlanes()[2].getBuffer();

        int ySize = yBuffer.remaining();
        int uSize = uBuffer.remaining();
        int vSize = vBuffer.remaining();

        nv21 = new byte[ySize + uSize + vSize];

        //U and V are swapped
        yBuffer.get(nv21, 0, ySize);
        vBuffer.get(nv21, ySize, vSize);
        uBuffer.get(nv21, ySize + vSize, uSize);

        return nv21;
    }

    private static byte[] NV21toJPEG(byte[] nv21, int width, int height) {
        ByteArrayOutputStream out = new ByteArrayOutputStream();
        YuvImage yuv = new YuvImage(nv21, ImageFormat.NV21, width, height, null);
        yuv.compressToJpeg(new Rect(0, 0, width, height), 100, out);
        return out.toByteArray();
    }
}

public final class FileManager {
    public static void writeFrame(String fileName, byte[] data) {
        try {
            BufferedOutputStream bos = new BufferedOutputStream(new FileOutputStream(fileName));
            bos.write(data);
            bos.flush();
            bos.close();
//            Log.e(TAG, "" + data.length + " bytes have been written to " + filesDir + fileName + ".jpg");
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}

Answer 2

我不确定，但我认为你只采用了YUV_420_888格式（亮度部分）的一个平面。

在我的情况下，我通常以这种方式将图像转换为byte []。

            Image m_img;
            Log.v(LOG_TAG,"Format -> "+m_img.getFormat());
            Image.Plane Y = m_img.getPlanes()[0];
            Image.Plane U = m_img.getPlanes()[1];
            Image.Plane V = m_img.getPlanes()[2];

            int Yb = Y.getBuffer().remaining();
            int Ub = U.getBuffer().remaining();
            int Vb = V.getBuffer().remaining();

            data = new byte[Yb + Ub + Vb];
            //your data length should be this byte array length.

            Y.getBuffer().get(data, 0, Yb);
            U.getBuffer().get(data, Yb, Ub);
            V.getBuffer().get(data, Yb+ Ub, Vb);
            final int width = m_img.getWidth();
            final int height = m_img.getHeight();

我使用这个字节缓冲区转换为rgb。

希望这会有所帮助。

干杯。垂发。

Answer 3

您的代码正在请求压缩的JPEG格式图像。它们的每个帧的大小都会发生变化，并且它们会比未压缩的图像小得多。如果除了保存JPEG图像之外什么都不做，你只需将byte []数据中的内容保存到磁盘即可。

如果您想要实际使用JPEG，可以使用BitmapFactory.decodeByteArray（）将其转换为Bitmap，例如，虽然效率很低。

或者你可以切换到效率更高的YUV，但你需要做更多工作才能从中获取Bitmap。

Android Camera2 API YUV_420_888到JPEG

3 个答案: