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I am making a cross platform Java application that uses Computer Vision (OpenCV). I need to receive video from a webcam. Currently using standard OpenCV methods:

VideoCapture videoCapture = new VideoCapture();
videoCapture.open(cameraIndex);
...
videoCapture.read(frame);

Of course, the native OpenCV library is loaded before accessing the camera:

System.loadLibrary(Core.NATIVE_LIBRARY_NAME);

The library was built with these arguments:

-D WITH_IPP=OFF \
-D BUILD_opencv_java=ON \
-D CMAKE_BUILD_TYPE=RELEASE \
-D CMAKE_INSTALL_PREFIX=../../opencv-4.5.3/build/install \
-D OPENCV_EXTRA_MODULES_PATH=../../opencv_contrib-4.5.3/modules \
-D BUILD_opencv_python2=OFF \
-D BUILD_opencv_python3=OFF \
-D INSTALL_PYTHON_EXAMPLES=OFF \
-D INSTALL_C_EXAMPLES=OFF \
-D OPENCV_ENABLE_NONFREE=ON \
-D BUILD_EXAMPLES=OFF \
-D OPENCV_JAVA_SOURCE_VERSION=1.8 \
-D OPENCV_JAVA_TARGET_VERSION=1.8 \
-D BUILD_SHARED_LIBS=OFF \
-D BUILD_FAT_JAVA_LIB=ON \
-D WITH_MATLAB=OFF \
-D BUILD_ZLIB=OFF \
-D BUILD_TIFF=OFF \
-D BUILD_JASPER=OFF \
-D BUILD_JPEG=OFF \
-D BUILD_PNG=OFF \
-D WITH_JPEG=OFF \
-D WITH_PNG=OFF \
-D WITH_OPENEXR=OFF \
-D BUILD_PERF_TESTS=OFF \
-D BUILD_TESTS=OFF \

The camera works on Windows 10 (x64) and Kali Linux (amd64). But but not on macOS.

After videoCapture.open(cameraIndex) function, an error message appears in the console and the application is closed:

OpenCV: not authorized to capture video (status 0), requesting...
OpenCV: can not spin main run loop from other thread, set OPENCV_AVFOUNDATION_SKIP_AUTH=1 to disable authorization request and perform it in your application.
OpenCV: camera failed to properly initialize!

I tried a lot of things such as export OPENCV_AVFOUNDATION_SKIP_AUTH=0 or Thread.sleep(1000) after videoCapture.open() or opening camera in another thread. Also i added Info.plist

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd">
<plist version="1.0">
<dict>
    <key>NSCameraUsageDescription</key>
    <string>Application needs permission to access the camera to capture images</string>
</dict>
</plist>

into src folder of my .jar. But nothing helped.

I have read these:

and many many other resources but there is still no answer.

I even tried using the OpenPVP-capture-java (https://github.com/openpnp/openpnp-capture-java) library, but that didn't help.

objc[2116]: Class PlatformAVCaptureDelegate is implemented in both /private/var/folders/zz/zyxvpxvq6csfxvn_n0000000000000/T/jna-3506402/jna6724263821710587077.tmp (0x14fac7cd8) and /private/var/folders/zz/zyxvpxvq6csfxvn_n0000000000000/T/jna-3506402/jna1573965830287255196.tmp (0x14faf9cd8). One of the two will be used. Which one is undefined.
2021-10-09 20:44:39.093 java[2116:99975] Requesting permission, bundle path for Info.plist: /Library/Java/JavaVirtualMachines/adoptopenjdk-8.jdk/Contents/Home/bin
zsh: abort      java -Djava.library.path=. -jar CamTest.jar

In the system settings, the terminal has access to the camera. Also, there is a problem with the camera on Ubuntu (after videoCapture.open(), the program freezes). But this is a topic for another question.

Is there a way to access the camera for OpenCV (Java) on macOS? Perhaps using some kind of third party cross platform library ...

Christoph Rackwitz
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F3RNI
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  • does any previous version of OpenCV succeed? does OpenCV from *Python* or C++, on your macOS system, succeed? do you happen to have an older version of macOS to test against? apart from that, if you can get access to the camera in *any* way, you can wrap the data in a cv::Mat using one of the constructors that take a data pointer and other values – Christoph Rackwitz Oct 10 '21 at 01:52
  • @ChristophRackwitz, OpenCV 4.5.1 also fails. `opencv-contrib-python` (installed via `pip3`) works great. As well as FaceTime and `imagesnap -w 1 snapshot.png` detects camera without problems. It looks like the problem is with java itself (maybe with JDK) – F3RNI Oct 10 '21 at 02:12
  • why would the "terminal" need permission, when it's just the terminal? I think java should request and be given permission, because it's the runtime. – Christoph Rackwitz Oct 10 '21 at 12:38

1 Answers1

-1

Again I answer my own question...

Thanks @ChristophRackwitz! After your question whether the camera works in python, I checked it (I don't know why I didn't do it before). And so, the camera in python (with opencv-contrib-python) works without problems, so I realized that the problem was with Java (JDK) itself.

I have JDK 8 installed with this commands:

brew tap adoptopenjdk/openjdk
brew install --cask adoptopenjdk8

So, my JAVA_HOME was /Library/Java/JavaVirtualMachines/adoptopenjdk-8.jdk/Contents/Home

I don’t know if it’s broken Java or something else, but when I installed Java11 with: brew install java11 and set JAVA_HOME to /usr/local/Cellar/openjdk@11/11.0.12/ It's finally working!

I spent so much time on this and the solution is just in the wrong Java version... This is strange, because my application (and .jar file) was compiled with JDK 8. And on other operating systems (Windows, Linux) everything works without problems with Java 8. Anyway, now when I start the application from the terminal, it requests access to the camera and everything works fine!

F3RNI
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  • @gpasch This is the solution for my problem. If you have the same problem, then your Java may be broken or not working properly on macOS. Try installing another JDK. There can be no other solution, because **inside OpenCV there is a function that asks for permission to access the camera.** If the JDK does not handle this request correctly, the camera permission cannot be obtained. This is not a problem with OpenCV. (If, of course, you build it correctly) – F3RNI Oct 13 '21 at 19:40