Develop Reference

Can't load OpenCV on Linux - undefined symbol error

So I would like to play with OpenCV little bit. My test project is in Java (OS is Debian Linux 8.4), and I have followed this tutorial to build OpenCV: https://opencv-java-tutorials.readthedocs.io/en/latest/01-installing-opencv-for-java.html
After fixing few issues, I was able to successfully build OpenCV jar and so file. There were no errors or warnings during the build. I have put opencv-400.jar and libopencv_java400.so into lib subfolder of my project. Added the jar file to build path in Eclipse, and put correct path to so file in Eclipse's Build Configurations.
My project has just a Main class which is a sample I found in OpenCV's sources, so nothing complicated:
import org.opencv.core.Core;
import org.opencv.core.CvType;
import org.opencv.core.Mat;
public class Main {
public static void main(String[] args) {
System.out.println("Welcome to OpenCV " + Core.VERSION);
System.loadLibrary(Core.NATIVE_LIBRARY_NAME);
Mat m = Mat.eye(3, 3, CvType.CV_8UC1);
System.out.println("m = " + m.dump());
}
}
It all looks that it should be working fine, but when I run the project, I see this exception:
Exception in thread "main" java.lang.UnsatisfiedLinkError: /home/firzen/ownCloud/develop/java/workspace/CVExperiments/lib/libopencv_java400.so: /home/firzen/ownCloud/develop/java/workspace/CVExperiments/lib/libopencv_java400.so: undefined symbol: _ZNK6google8protobuf8internal12MapFieldBase28SpaceUsedExcludingSelfNoLockEv
at java.lang.ClassLoader$NativeLibrary.load(Native Method)
at java.lang.ClassLoader.loadLibrary0(ClassLoader.java:1938)
at java.lang.ClassLoader.loadLibrary(ClassLoader.java:1854)
at java.lang.Runtime.loadLibrary0(Runtime.java:870)
at java.lang.System.loadLibrary(System.java:1122)
at Main.main(Main.java:9)
And this part of exception is really making me worried:
/home/firzen/ownCloud/develop/java/workspace/CVExperiments/lib/libopencv_java400.so: undefined symbol: _ZNK6google8protobuf8internal12MapFieldBase28SpaceUsedExcludingSelfNoLockEv
It almost seems to me that there is something wrong with that libopencv_java400.so file. Am I right? Or do I need some another files to make it work? I have build OpenCV as Debug, so that so file has 135 MiB, but that shouldn't be a problem I think.
I will be thankful for any ideas!

That error means that your system does not have a suitable protobuf library installed. You might give sudo apt install libprotobuf10 a try, although I can't guarantee that will help.
Alternatively, you can also run ldd /home/firzen/ownCloud/develop/java/workspace/CVExperiments/lib/libopencv_java400.so, which will show you all libraries OpenCV tries to import - perhaps Protobuf has actually been built along with OpenCV, but is just not installed.

Ensuring files are available to the JVM

I'm trying to install TensorFlow for Java on Windows 10 using this Article
. I followed the steps carefully but the windows commands didn't work with me so I decided to do it manually.
The first command is to make the .jar part of the classpath and I did it manually
but the second step was to ensure that the following two files are available to the JVM: the .jar file and the extracted JNI library
but I don't know how to do that manually
The code:
package securityapplication;
import org.tensorflow.TensorFlow;
import org.tensorflow.Graph;
import org.tensorflow.Session;
import org.tensorflow.Tensor;
public class SecurityApplication {
public static void main(String[] args) throws Exception {
try (Graph g = new Graph()) {
final String value = "Hello from " + TensorFlow.version();
// Construct the computation graph with a single operation, a constant
// named "MyConst" with a value "value".
try (Tensor t = Tensor.create(value.getBytes("UTF-8"))) {
// The Java API doesn't yet include convenience functions for adding operations.
g.opBuilder("Const", "MyConst").setAttr("dtype", t.dataType()).setAttr("value", t).build();
}
// Execute the "MyConst" operation in a Session.
try (Session s = new Session(g);
Tensor output = s.runner().fetch("MyConst").run().get(0)) {
System.out.println(new String(output.bytesValue(), "UTF-8"));
}
}
}
}
could someone help? cuz my program that uses TensorFlow still have the following error
The text in the image is :
Exception in thread "main" java.lang.UnsatisfiedLinkError: Cannot find TensorFlow native library for OS: windows, architecture: x86. See https://github.com/tensorflow/tensorflow/tree/master/tensorflow/java/README.md for possible solutions (such as building the library from source). Additional information on attempts to find the native library can be obtained by adding org.tensorflow.NativeLibrary.DEBUG=1 to the system properties of the JVM.
at org.tensorflow.NativeLibrary.load(NativeLibrary.java:66)
at org.tensorflow.NativeLibrary.load(NativeLibrary.java:66)
at org.tensorflow.TensorFlow.init(TensorFlow.java:36)
at org.tensorflow.TensorFlow.<clinit>(TensorFlow.java:40)
at org.tensorflow.Graph.<clinit>(Graph.java:194)
at securityapplication.SecurityApplication.main(SecurityApplication.java:15) Java Result: 1 BUILD SUCCESSFUL (total time: 4 seconds)
The result after running the first command in cmd:
The result after running the second command in Windows PowerShell:
Any suggestions?!
Thank you

The first command failure (javac) suggests that the javac command is not in your PATH environment variables. See for example, this StackOverflow question
For the second command failure, I believe the space after -D is what is causing you trouble as Holger suggested.
IDEs like Eclipse and others also provide a means to set the java.library.path property for the JVM (see this StackOverflow answer for example).
Background: TensorFlow for Java consists of a Java library (packaged in a .jar file) and a native library (.dll on Windows, distributed in a .zip file). You need to ensure that the .jar file is in the classpath and the directory containing the .dll is in included in the java.library.path of the JVM when executing a program.
Hope that helps.

ACM Library simple example not working with jdk 1.7.0_79

Hi All java Experts!
When I tried a little example of acm library
import acm.program.*;
class prog extends ConsoleProgram {
public void run() {
int number = readInt("?");
println("You entered: " number);
}
}
It compiled successfully.
I used commandline like this:
javac -cp acm.jar; main.java
java -cp acm.jar; prog
But I got this error:
Exception in thread "main" java.lang.UnsatisfiedLinkError: acm.util.DOSCommandLi
ne.getLine()Ljava/lang/String;
at acm.util.DOSCommandLine.getLine(Native Method)
at acm.util.DOSCommandLine.getCommandLine(JTFTools.java:1627)
at acm.util.JTFTools.getCommandLine(JTFTools.java:439)
at acm.util.JTFTools.getMainClass(JTFTools.java:464)
at acm.program.Program.main(Program.java:1320)
What does it mean... I think the JDK version problem.... however I am using JDK 'jdk1.7.0_79'
In my opinion It is throwing exception only for this JDK version. Request to try you and give feedback.
Thanks...

Solved!
It doesn't require any native library...
What I had to do was to Use main entry as:
public static void main(String[] args) {
new prog().start(args);
}
Adding after 'run' method it works now. Note: this line 'new prog().start(args);'
This solution found here:
http://www.dreamincode.net/forums/topic/240789-acmjar-package-problem-class-wasnt-find-in-project/
Thanks Choppy
But it took me considerable time Hushhhhh.....

UnsatisfiedLinkError at Native Method means that there is no native library (for windows it would be dll) loaded which could be called for your acm.util.DOSCommandLine.getLine() method.
With your library there should be native packages, which will contain native libraries for your system architecture. You have to put one of these into your classpath folder.

Running Java OpenCV on Ubuntu from command line

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?

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.

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

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

Cannot use installed java 3d

hi i'm trying to use java 3d in both command prompt and in netbeans. I have a win8 64 bit computor. I installed j3d-1_5_2-windows-amd64.exe. and it got installed inside java folder in a folder called Java3D. then I added an environmental variable as CLASSPATH and the values are C:\Program Files\Java\Java3D\1.5.2\lib\ext\j3dcore.jar;C:\Program Files\Java\Java3D\1.5.2\lib\ext\j3dutils.jar;C:\Program Files\Java\Java3D\1.5.2\lib\ext\vecmath.jar.
my file get compilled without errors when I try to runit from command prompt using the command java -cp . Hello3d it gives a calss not found error for javax/media/j3d/Node. and when i try to import 3d libraries from netbeans it gives an error on j3d after import com.sun. the following is the class I compiled from command prompt. please tell me what i'm doing wrong. thanx in advance
import com.sun.j3d.utils.universe.SimpleUniverse;
import com.sun.j3d.utils.geometry.ColorCube;
import javax.media.j3d.BranchGroup;
public class Hello3d {
public Hello3d()
{
SimpleUniverse universe = new SimpleUniverse();
BranchGroup group = new BranchGroup();
group.addChild(new ColorCube(0.3));
universe.getViewingPlatform().setNominalViewingTransform();
universe.addBranchGraph(group);
}
public static void main( String[] args ) {
new Hello3d();
}
} // end of class Hello3d

You use an obsolete version (1.5.2) of Java3D, this version is no longer maintained since a few years. Please uninstall it and install the latest version (1.6.0). Follow my instructions here.

Your code runs perfectly in my eclipse environment using java3d version 1.5.2.
It shows an ugly cube seen from one side only, red faced.
I guess you need to set the path to the native libraries that java3d needs.
Regrettably, I don't know how to do this on windows (R).
Regrettably I have not enough reputation to put this into a comment rather than an answer.
If anyone with enough reputation cares, please turn this answer into a comment.