Android Camera2 YUV to RGB conversion turns out green?

edit

I have been able to do it successfully.

    Image.Plane Y = image.getPlanes()[0];
    Image.Plane U = image.getPlanes()[1];
    Image.Plane V = image.getPlanes()[2];

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

    byte[] data = new byte[Yb + Ub + Vb];

    Y.getBuffer().get(data, 0, Yb);
    U.getBuffer().get(data, Yb, Ub);
    V.getBuffer().get(data, Yb+ Ub, Vb);

I'm using OpenCV JNI and was able to convert it to BGR image using CV_YUV2BGR_I420 with cvtColor

Here's my C++ code.

jboolean Java_com_fenchtose_myPackage_myClass_myMethod(
        JNIEnv* env, jobject thiz,
        jint width, jint height,
        jbyteArray YUVFrameData)
{
    jbyte * pYUVFrameData = env->GetByteArrayElements(YUVFrameData, 0);

    double alpha;
    alpha = (double) alphaVal;

    Mat mNV(height + height/2, width, CV_8UC1, (unsigned char*)pYUVFrameData);
    Mat mBgr(height, width, CV_8UC3);

    cv::cvtColor(mNV, mBgr, CV_YUV2BGR_I420);

    env->ReleaseByteArrayElements(YUVFrameData, pYUVFrameData, 0);

    return true;
}

I have a image(YUV_420_888) that captured by ARCore in pixel, and want to covert it to Mat.

I have try the first answer(http://answers.opencv.org/ques..., but it failed.I can't get the rgb image by save the picture using the opencv function: imwrite().

And then, I try the second answer(http://answers.opencv.org/ques..., I failed too. because in the image that saved by imwrite(), red object covert to green.

Finally, because of a little accident, I try the code that YUV to data(byte[]) that write in the first answer, and try the code that data(byte[]) to Mat that writes in the second answer, and I successd.

---------- Java

    Image.Plane Y = image.getPlanes()[0];
    Image.Plane U = image.getPlanes()[1];
    Image.Plane V = image.getPlanes()[2];

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

    byte[] data = new byte[Yb + Ub + Vb];

    Y.getBuffer().get(data, 0, Yb);
    U.getBuffer().get(data, Yb, Ub);
    V.getBuffer().get(data, Yb+ Ub, Vb);

    return data;

--------- OpenCV JNI ,c++

extern "C"
JNIEXPORT jintArray JNICALL
Java_com_google_ar_core_examples_java_helloar_HelloArActivity_getKeyPoint2
    (JNIEnv *env, jobject jobj, jbyteArray _pixels1, jbyteArray _pixels2, jint width, jint height)
{

jbyte *pixels1 = env->GetByteArrayElements(_pixels1 , NULL);
jbyte *pixels2 = env->GetByteArrayElements(_pixels2 , NULL);

if(pixels1==NULL){
    int size = -1;
    jintArray result = env->NewIntArray(size);
    return result;
}
Mat lyuvMat(height + (height / 2), width, CV_8UC1, (unsigned char*)pixels1);
imwrite("/storage/emulated/0/camoutput/xly/lyuv.jpg", lyuvMat);
Mat lrgbMat(height, width, CV_8UC3);
cvtColor(lyuvMat, lrgbMat, COLOR_YUV2RGB_NV21, 3);
imwrite("/storage/emulated/0/camoutput/xly/lrgb.jpg", lrgbMat);



.......

}

COLOR_YUV420sp2BGRA 或许你应该使用这个答案，我在face 上也有部分有色变绿，希望对你有用。

Camera2 YUV_420_888 to RGB Mat(opencv) in Java

@Override
public void onImageAvailable(ImageReader reader){
    Image image = null;

    try {
        image = reader.acquireLatestImage();
        if (image != null) {

            byte[] nv21;
            ByteBuffer yBuffer = mImage.getPlanes()[0].getBuffer();
            ByteBuffer uBuffer = mImage.getPlanes()[1].getBuffer();
            ByteBuffer vBuffer = mImage.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);

            Mat mRGB = getYUV2Mat(nv21);



        }
    } catch (Exception e) {
        Log.w(TAG, e.getMessage());
    }finally{
        image.close();// don't forget to close
    }
}



public Mat getYUV2Mat(byte[] data) {
Mat mYuv = new Mat(image.getHeight() + image.getHeight() / 2, size.getWidth(), CV_8UC1);
mYuv.put(0, 0, data);
Mat mRGB = new Mat();
cvtColor(mYuv, mRGB, Imgproc.COLOR_YUV2RGB_NV21, 3);
return mRGB;}

• Read Y, U and V binary files into byte buffers
  • Create OpenCV Mat object from the created buffers.
  • Resize U and V Mats to the size of Y.
  • Merge Y and resized U and V.
  • Convert from YUV to BGR

Size actual_size(1280, 720);
Size half_size(1280/2, 720/2); //Size half_size(1280/2, 720/2);
Mat ndk_rgb_img, ndk_rgb_img_out;
int ndk_image_width = 1280; 
int ndk_image_height = 720;
uint8_t *yPixel, *uPixel, *vPixel;
int32_t yLen, uLen, vLen;
int32_t uvPixelStride;
int32_t uvRowStride;



AImage_getPlaneData(image, 0, &yPixel, &yLen); //Y
AImage_getPlaneData(image, 1, &uPixel, &uLen); // U
AImage_getPlaneData(image, 2, &vPixel, &vLen); //V
AImage_getPlanePixelStride(image, 1, &uvPixelStride); // foulée en pixel
AImage_getPlaneRowStride (image, 1, &uvRowStride); // foulée en ligne

// cout << "length Y " <<  yLen << endl;
// cout << "length U " << uLen << endl;
// cout << "length V " <<  vLen << endl;
//cout << "uvPixelStride " <<  uvPixelStride << endl;
//cout << "uvRowStride " <<  uvRowStride << endl;

Mat y(actual_size, CV_8UC1, yPixel);
Mat u(half_size, CV_8UC2, uPixel); 
Mat v(half_size, CV_8UC2, vPixel); 
long addr_diff = u.data - v.data;
if (addr_diff > 0) { 
    assert(addr_diff == 1); 
    cvtColorTwoPlane(y, u, ndk_rgb_img, COLOR_YUV2BGR_NV12); //COLOR_YUV2RGB_NV12
} else { 
    assert(addr_diff == -1); 
    cvtColorTwoPlane(y, v, ndk_rgb_img, COLOR_YUV2BGR_NV21); 
}

Work for me very well

The answer http://answers.opencv.org/question/61... did not fully work for me, it seems that the data format can vary between devices.

The mentioned answer probably works if the pixel stride is 1, but all devices I have available produce images with pixel stride 2 (Nexus 5, Sony Xperia Z3). The pixel stride means that the U and V planes are padded. The full buffer has the size of 2 bytes per pixel.

There is no way to directly convert this padded format with OpenCV currently, but it can be converted to YUV NV21 before converting it to a RGB/BGR image. (NV21 because it requires less work to convert to NV21 than to normal YUV420).

I do not know if a different pixel stride than 1 or 2 is possible (i guess not).

@TargetApi(21)
public Mat convertYuv420888ToMat(Image image, boolean isGreyOnly) {
    int width = image.getWidth();
    int height = image.getHeight();

    Image.Plane yPlane = image.getPlanes()[0];
    int ySize = yPlane.getBuffer().remaining();

    if (isGreyOnly) {
        byte[] data = new byte[ySize];
        yPlane.getBuffer().get(data, 0, ySize);

        Mat greyMat = new Mat(height, width, CvType.CV_8UC1);
        greyMat.put(0, 0, data);

        return greyMat;
    }

    Image.Plane uPlane = image.getPlanes()[1];
    Image.Plane vPlane = image.getPlanes()[2];

    // be aware that this size does not include the padding at the end, if there is any
    // (e.g. if pixel stride is 2 the size is ySize / 2 - 1)
    int uSize = uPlane.getBuffer().remaining();
    int vSize = vPlane.getBuffer().remaining();

    byte[] data = new byte[ySize + (ySize/2)];

    yPlane.getBuffer().get(data, 0, ySize);

    ByteBuffer ub = uPlane.getBuffer();
    ByteBuffer vb = vPlane.getBuffer();

    int uvPixelStride = uPlane.getPixelStride(); //stride guaranteed to be the same for u and v planes
    if (uvPixelStride == 1) {
        uPlane.getBuffer().get(data, ySize, uSize);
        vPlane.getBuffer().get(data, ySize + uSize, vSize);

        Mat yuvMat = new Mat(height + (height / 2), width, CvType.CV_8UC1);
        yuvMat.put(0, 0, data);
        Mat rgbMat = new Mat(height, width, CvType.CV_8UC3);
        Imgproc.cvtColor(yuvMat, rgbMat, Imgproc.COLOR_YUV2RGB_I420, 3);
        yuvMat.release();
        return rgbMat;
    }

    // if pixel stride is 2 there is padding between each pixel
    // converting it to NV21 by filling the gaps of the v plane with the u values
    vb.get(data, ySize, vSize);
    for (int i = 0; i < uSize; i += 2) {
        data[ySize + i + 1] = ub.get(i);
    }

    Mat yuvMat = new Mat(height + (height / 2), width, CvType.CV_8UC1);
    yuvMat.put(0, 0, data);
    Mat rgbMat = new Mat(height, width, CvType.CV_8UC3);
    Imgproc.cvtColor(yuvMat, rgbMat, Imgproc.COLOR_YUV2RGB_NV21, 3);
    yuvMat.release();
    return rgbMat;
}