Running Java OpenCV on Ubuntu from command line

Question

I'm trying to compile and run a simple example of Java code using OpenCV library, on Ubuntu 14.04 64bits, found in OpenCV's documentation: Java OpenCV Documentation

import org.opencv.core.Core;
import org.opencv.core.Mat;
import org.opencv.core.CvType;
import org.opencv.core.Scalar;

class SimpleSample
{
    static
    {
        System.loadLibrary(Core.NATIVE_LIBRARY_NAME);
    }

    public static void main(String[] args)
    {
        System.out.println("Welcome to OpenCV " + Core.VERSION);
        Mat m = new Mat(5, 10, CvType.CV_8UC1, new Scalar(0));
        System.out.println("OpenCV Mat: " + m);
        Mat mr1 = m.row(1);
        mr1.setTo(new Scalar(1));
        Mat mc5 = m.col(5);
        mc5.setTo(new Scalar(5));
        System.out.println("OpenCV Mat data:\n" + m.dump());
    }
}

Since it is just a simple test, I really don't want to use any sophisticated building system. So I'm compiling with the following command:

javac -cp "/usr/share/OpenCV/java/opencv-248.jar" SimpleSample.java

However I'm unable to run the application, because when I call: java SimpleSample

I face the following exception:

Exception in thread "main" java.lang.NoClassDefFoundError: org/opencv/core/Core

at SimpleSample.<clinit>(SimpleSample.java:10)

Caused by: java.lang.ClassNotFoundException: org.opencv.core.Core
at java.net.URLClassLoader.findClass(URLClassLoader.java:381)
at java.lang.ClassLoader.loadClass(ClassLoader.java:424)
at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:331)
at java.lang.ClassLoader.loadClass(ClassLoader.java:357)
... 1 more

Can someone help me running this application?

Dukefirehawk · Accepted Answer · 2016-01-09 18:24:23Z

2

The opencv-248.jar is not on the CLASSPATH. You can run it as follows:

java -cp /usr/share/OpenCV/java/opencv-248.jar:. SimpleSample

Compile from the source and copy libopencv_java248.so into $JAVA_HOME/jre/lib/amb64/ directory. This platform specific file is not included in the jar file. Running the sample program without this file installed would get "java.lang.UnsatisfiedLinkError: no opencv_java248 in java.library.path" error. Also note that Apache Ant need to be installed for this platform specific file to be generated during compilation.

edited Jan 9, 2016 at 18:24

answered Jan 8, 2016 at 17:33

Dukefirehawk

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2 Comments

Fernando Over a year ago

This doesn't work. java -cp /usr/share/OpenCV/java/opencv-248.jar:. SimpleSample Exception in thread "main" java.lang.UnsatisfiedLinkError: no opencv_java248 in java.library.path at java.lang.ClassLoader.loadLibrary(ClassLoader.java:1864) at java.lang.Runtime.loadLibrary0(Runtime.java:870) at java.lang.System.loadLibrary(System.java:1122) at SimpleSample.<clinit>(SimpleSample.java:10)

Dukefirehawk Over a year ago

You need to install libopencv_java248.so in your $JAVA_HOME/jre/lib/amb64/ directory for the opencv-248.jar to work. To get libopencv_java248.so, compile it from the source.

Fernando · Accepted Answer · 2016-01-11 11:42:00Z

1

I managed to solve the problem. In Ubuntu 14.04 64bit you can run the code from command line with the following command:

LD_LIBRARY_PATH=/usr/lib/jni/ java -cp /usr/share/OpenCV/java/opencv-248.jar:. SimpleSample

answered Jan 11, 2016 at 11:42

Fernando

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Comments

Freeman · Accepted Answer · 2019-09-05 15:35:18Z

0

The OpenCV native binary library path (in my case libopencv_java343.dylib) can be defined with -D:

java -cp /opt/local/share/OpenCV/java/opencv-343.jar:. -Djava.library.path=/opt/local/share/OpenCV/java/ SimpleCV

edited Sep 5, 2019 at 15:35

answered Sep 5, 2019 at 9:45

Freeman

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