Andrey Pavlenko's profile - activity

http://docs.opencv.org/master/d7/dbd/...

https://github.com/Itseez/opencv/tree...

OpenCV for Android is built using Android NDK. Do you know anything about NDK version supporting compilation for Android x86_64?

The new viz module exists in OpenCV-2.4.9 sources but was not included into pre-built libraries since it depends on VTK that assumes redistribution of pre-built VTK with the package.

For those who needs the viz module we suggest building OpenCV-2.4.9 from sources with -DWITH_VTK=ON CMake option. (Use -DVTK_DIR=/your/vtk/build/path to help CMake finding VTK).

hi, i use ndk-build to compile my opencv code for android.I have successful experience on the work.but,today i fail to success.this is my log under ndk-build:

 /cygdrive/e/EclipseSomkeDetect/obj/local/armeabi/libopencv_androidcamera.a(camera_activity.o):
In function 'CameraWrapperConnector::getPathLibFolder()': camera_activity.cpp:
(.text._ZN22CameraWrapperConnector16getPathLibFolderEv+0x38): 
undefined reference to 'dladdr' 
collect2: ld returned 1 exit status /cygdrive/d/android-ndk-r4-crystax/build/core/build-shared-library.mk:38: 
recipe for target '/cygdrive/e/EclipseSomkeDetect/obj/local/armeabi/libSmokeDetect.so' failed
make: *** [/cygdrive/e/EclipseSomkeDetect/obj/local/armeabi/libSmokeDetect.so] Error 1

could any expert tell me what is problem?several weeks ago,i compile opencv code successfully which include no cvcapture func .My current c++ code uses cvcapture func and could not link successfully.any message would be appreciated. someone tells you should add app_platform:=android-8 in application.mk,i try,but i fail.

What I would suggest first: please use the latest NDK (r9d), the latest OpenCV4Android SDK (2.4.8 or even coming soon 2.4.9) and don't use Cygwin. Start from here: http://docs.opencv.org/doc/tutorials/introduction/android_binary_package/android_dev_intro.html

Have you read the items 9 and 10 from http://docs.opencv.org/doc/tutorials/introduction/android_binary_package/android_dev_intro.html#building-application-native-part-from-eclipse-cdt-builder ?

still getting the same error as i mentioned in links , it runs in first time but when i click on DetectionBasedTracker_jni.cpp it showing me error on

  # include < string >
  # include < vectotr >
  # include < jni.h >

Are you going to use 'core' and 'imgproc' in JNI C++ code or in Java code?

OpenCV has WinRT support, no plans for Win Phone 8 for today.

//C++/JNI
//vector_Point2f

void Mat_to_vector_Point2f(Mat& mat, vector<Point2f>& v_point)
{
    v_point.clear();
    CHECK_MAT(mat.type()==CV_32FC2 && mat.cols==1);
    v_point = (vector<Point2f>) mat;
}

void vector_Point2f_to_Mat(vector<Point2f>& v_point, Mat& mat)
{
    mat = Mat(v_point, true);
}

// C++ / JNI
// vector_KeyPoint converters

void Mat_to_vector_KeyPoint(Mat& mat, vector<KeyPoint>& v_kp)
{
    v_kp.clear();
    CHECK_MAT(mat.type()==CV_32FC(7) && mat.cols==1);
    for(int i=0; i<mat.rows; i++)
    {
        Vec<float, 7> v = mat.at< Vec<float, 7> >(i, 0);
        KeyPoint kp(v[0], v[1], v[2], v[3], v[4], (int)v[5], (int)v[6]);
        v_kp.push_back(kp);
    }
    return;
}


void vector_KeyPoint_to_Mat(vector<KeyPoint>& v_kp, Mat& mat)
{
    int count = (int)v_kp.size();
    mat.create(count, 1, CV_32FC(7));
    for(int i=0; i<count; i++)
    {
        KeyPoint kp = v_kp[i];
        mat.at< Vec<float, 7> >(i, 0) = Vec<float, 7>(kp.pt.x, kp.pt.y, kp.size, kp.angle, kp.response, (float)kp.octave, (float)kp.class_id);
    }
}

Hi, I am doing some Structure-from-Motion approach and having some trouble getting R and T from the essential matrix.

So far I am doing the following steps:

• Calibrate Camera
• Take two images with the same camera
• undistort images
• find feature points
• match features
• calculate fundamental matrix F using Mat fundamental = Calib3d.findFundamentalMat(object_left, object_right);

• Calculate essential matix E using the following block of code:

  Mat E = new Mat();
  Core.multiply(cameraMatrix.t(),fundamental, E);
  Core.multiply(E, cameraMatrix, E);
  

Using E I now need to calculate R and T, the relative rotation and translation between both cameras. I've read the chapter about SCV and E in Hartley and Zisserman, but now I am struggeling with OpenCV Code. A quick google-question brought me this code which is in C++:

Matx34d P;
//decompose E 
SVD svd(E,SVD::MODIFY_A);
Mat svd_u = svd.u;
Mat svd_vt = svd.vt;
Mat svd_w = svd.w;
Matx33d W(0,-1,0,1,0,0,0,0,1);//HZ 9.13
Mat_<double> R = svd_u * Mat(W) * svd_vt; //
Mat_<double> T = svd_u.col(2); //u3

if (!CheckCoherentRotation (R)) {
  std::cout<<"resulting rotation is not coherent\n";
  return 0;
}

The problem is now that I don't know how to transfer this code to Android/Java. There is no object SVD. I am doing the SVD for E using Mat svd = E.inv(Core.DECOMP_SVD); which returns a Mat Object.

Can someone help me please? I need access to U, W and VT from the singular value decomposition.

I use example code as following to try open MP4 video file and put some text to video file but open result always return failed.

extern "C"
{
//.... something code............

const char* arrURL = "mnt/sdcard/Download/VID_20140317_104750.mp4";
string source(arrURL);

VideoCapture inputVideo;              // Open input
//inputVideo.open(source);

if (!inputVideo.open(source)) -> alway return false here...
{
    env->ReleaseStringUTFChars(URL, arrURL);
    env->ReleaseStringUTFChars(sInputText, arrInputText);
    return;
}
//....

i used eclipse CDT - juno, NDK-r9, OpenCV 2.4.8 do everyone can help me answer some questions? - VideoCapture can not be supported on android? - Do you know any other solution on android? (not FFMPEG lib)

Thanks

https://github.com/Itseez/opencv/pull/2541

JNB, thanks!

I started to use cv::format() a while ago to format my data in a CSV like text stream, and noticed it worked oddely : no problem of importance when used on a N * P cv::Mat where P is greater or equal to 2. The only matter then would be the useless spaces before each row but the first, but we can trim them afterwards easily.

But when P is equal to 1 (the matrix is a column), cv::format() does not seem to add the end of line signals between lines and I end up with a single line full of characters with no separation in between.

Here is an exemple, where I fill up two matrices and display them before and after using cv::format() :

#include <iostream>
#include "opencv2/opencv.hpp"

using namespace std;

int main()
{
  int dimensions = 5;
  int sampleCount = 4;

  cv::Mat points(sampleCount,dimensions, CV_32F,cv::Scalar(10));
  cout<<points<<endl;
  cout<<cv::format(points,"csv")<<endl;

  cv::Mat points2(sampleCount,1, CV_32F,cv::Scalar(10));
  cout<<points2<<endl;
  cout<<cv::format(points2,"csv")<<endl;

  return 0;
}

The output given is :

[10, 10, 10, 10, 10;
  10, 10, 10, 10, 10;
  10, 10, 10, 10, 10;
  10, 10, 10, 10, 10]
10, 10, 10, 10, 10
  10, 10, 10, 10, 10
  10, 10, 10, 10, 10
  10, 10, 10, 10, 10

[10; 10; 10; 10]
10101010

The extra spaces in the first case seem to come from the << operator which gives a nicer display since it displays a bracket on first line.

As for the second and most important case, I don't know where it comes from but I think this should be fixed.

Note the "csv" format seems not to be the only one with this kind of output, I tried with "python" and got a similar [10101010] output.

By 3.0 release we plan to keep a single license text as the 'opencv/LICENSE' (3-clause BSD) file and just reference it in every source file. The work is just started: https://github.com/Itseez/opencv/pull/2000

Probably because OpenCV4Android dev team has other priorities now. But you or somebody else are welcome to contribute OpenCL support for Android.

I believe the best practice is to use Java code for assets extraction (like the OpenCV sample does). But if you really need it in JNI, try the approach mentioned at http://stackoverflow.com/questions/13317387/how-to-get-file-in-assets-from-android-ndk

Probably the following code will give you an idea:

//==== storing data ====
FileStorage fs(".xml", FileStorage::WRITE + FileStorage::MEMORY);
fs << "date" << date_string << "mymatrix" << mymatrix;
string buf = fs.releaseAndGetString();

//==== reading it back ====
FileStorage fs(buf, FileStorage::READ + FileStorage::MEMORY);
fs["date"] >> date_string;
fs["mymatrix"] >> mymatrix;

I suggest you submit a bugs against CUDA and OCL SURF (reproducer is appreciated) if you'd like to see the problem fixed.

Have you tried to print to STDERR?

fprintf(stderr, ...);

I suggest you use cv::threshold(THRESH_BINARY).

@TimeManx No, it's not possible: Mat reallocates its buffer on native level when needed, so it's hard to share it between native and java without copying...

Maybe the following tutorial will look better for you?

http://www.anlak.com/opencv-java-with-eclipse/

OpenCV camera support may not work on some devices due to Android OS vendor customization. In particular it happens on some TI-based hardware like the 'Panasonic SoftBank 102P' is. Also you can provide logcat for deeper analysis.

The returned Mat is of N*1 size (where N is a number of non-zero elements of input Mat) and each of its elements contains row & col of non-zero element of input Mat. Consider it as an array non-zero pixels indexes.

There are plans to add a simple AR Android sample to OpenCV, but now we don't have it. I suggest you look at the "Mastering OpenCV with Practical Computer Vision Projects" book and its samples on GitHub.

Also try the OpenCV 2.4.6 (not .1).

Mat mat565(height, width, CV_8UC2, pixels);
Mat graymat;
cvtColor(mat565, graymat, COLOR_BGR5652GRAY);