Using OpenCV in Java with JavaCV

Question

I am getting desperate !! I am trying to use OpenCV in Java, via JavaCV (JNA to wrap OpenCV for java).

I am on Mac Os X 1.5.

I installed OpenCV, and I can compile and run the examples included. So that works.

Now I open Eclipse, and I create a new project, as described here : http://code.google.com/p/javacv/

In that new project, only one small class with a call to a opencv function (I used the sample code) :

import static name.audet.samuel.javacv.jna.cxcore.*;
import static name.audet.samuel.javacv.jna.cv.*;
import static name.audet.samuel.javacv.jna.highgui.*;
import static name.audet.samuel.javacv.jna.cvaux.*;

public class Test {
    public static void main(String[] args) {
        IplImage image = cvLoadImage("test.png", 1);
        if (image == null) {
            System.err.println("Could not load image file.");
        } else {
            cvSmooth(image, image, CV_GAUSSIAN, 3, 0, 0, 0);
            // ...
        }
    }
}

When I run it, I have the following error :

Exception in thread "main" java.lang.UnsatisfiedLinkError: Unable to load library 'cxcore': dlopen(libcxcore.dylib, 9): image not found

Please, I need help, I looked over google for hours, I don't know where to look for anymore.

Answer 1

It turned out the SVN version was not compatible with JavaCV.

I downloaded the latest official version (2.1) and compiled it and installed it, and it works.

See http://code.google.com/p/javacv/issues/detail?id=19

Answer 2

You need to link these two libraries:

- javacpp.jar
- javacv.jar

In the JavaCV/lib-opencv/win_x86_64 you have to have files of your like:

 - msvcp100.dll
 - msvcr100.dll
 - opencv_core220.dll
 - opencv_calib3d220.dll
 - ...

These DLLs have to be compiled for your platform (win 32 / win 64 / Linux / etc.

You have to define path to your OpneCV DLL files:

-Djava.library.path=lib-opencv/win_x86_64/
- or the DLLs have to be somewhere in your system PATH of your operating system

Answer 3

I had looked at this problem for a while, as the OP suggests all kinds of problems start crawling out of the woodwork. I went through a ton of StackOverflow posts to be able to come up with a relatively painless experience for setting up a OpenCV project in Java. I went through JavaCV and found that it did not meet my needs. I was however able to directly implement functionality referenced in OpenCV posts (C++ posts) but in the Java language when I used certain javacpp versions. I had a ton of compilation issues too since javacpp depends on compiled C++ libraries that must be native to the environment the user is in (something people that live in Java land love to not deal with). Anyway I was able to construct and environment with Maven. I use eclipse but this should work fine with other programming environments. I put up an example project to illustrate how to start build a bootstrap project and start working. The project compares 2 images, given their URLs. It's a equality test, wither the images are identical or not. Hopefully this can help folks setup and get working in this environment and avoid the tons and tons of pitfalls that I encountered when trying to work with OpenCV in Java (I was in the exact same place as OP mentally at that time :) ).

The example: https://github.com/darkhipo/ImgzCmp