MotionDetector example to JavaFX?

[mjackstone6]

Hello,

I am currently working through the MotionDetector sample at "https://github.com/bytedeco/javacv/blob/master/samples/MotionDetector.java" but I am having trouble getting this into JavaFX.

The part I am having trouble with is displaying each frame into an ImageView rather than a CanvasFrame. I used a JavaFXFrameConverter to convert IplImage but I got an error where it only supports 3 channels so I modified the code to create an IplImage with 3 channels. When running the code, I run into "The crash happened outside the Java Virtual Machine in native code."

Is there a better a way to do this example properly in JavaFX?

I have modified the code into:

@FXML
public void play() throws FrameGrabber.Exception {
    OpenCVFrameGrabber grabber = new OpenCVFrameGrabber("test.mp4");
    OpenCVFrameConverter.ToIplImage converter = new OpenCVFrameConverter.ToIplImage();
    grabber.start();

    IplImage frame = converter.convert(grabber.grab());
    IplImage image = null;
    IplImage prevImage = null;
    IplImage diff = null;

    JavaFXFrameConverter frameConverter = new JavaFXFrameConverter();

    CvMemStorage storage = CvMemStorage.create();

    while ((frame = converter.convert(grabber.grab())) != null) {
        cvClearMemStorage(storage);

        cvSmooth(frame, frame, CV_GAUSSIAN, 9, 9, 2, 2);
        if (image == null) {
            image = IplImage.create(frame.width(), frame.height(), IPL_DEPTH_8U, 3);
            cvCvtColor(frame, image, CV_RGB2GRAY);
        } else {
            prevImage = image;
            image = IplImage.create(frame.width(), frame.height(), IPL_DEPTH_8U, 3);
            cvCvtColor(frame, image, CV_RGB2GRAY);
        }

        if (diff == null) {
            diff = IplImage.create(frame.width(), frame.height(), IPL_DEPTH_8U, 3);
        }

        if (prevImage != null) {
            // perform ABS difference
            cvAbsDiff(image, prevImage, diff);
            // do some threshold for wipe away useless details
            cvThreshold(diff, diff, 64, 255, CV_THRESH_BINARY);

            Frame f = converter.convert(diff);
            Image im = frameConverter.convert(f);

            Platform.runLater(() -> mediaView.setImage(im));

        }
    }
    grabber.stop();

}

[teocci]

can you be more specific about your error? I mean in which line the exception occurred? what is the error you got? did you got something like this signal 11 (SIGSEGV)??

[saudet]

The cause of this issue is probably similar to bytedeco/javacpp#272. I've just fixed this for IplImage as well, so please give it a try with the snapshots: http://bytedeco.org/builds/

It is also possible to work around this by making sure that OpenCVFrameConverter doesn't get deallocated, by storing it in a field, for example.

In any case, IplImage is deprecated, so I would recommend switching to Mat anyway.

[mjackstone6]

I've tried testing on a snapshot and also converting to a field but I get the same error.
Here is the log file: https://pastebin.com/ZrZnDBwA

All the examples I've seen are using IplImage so I'm confused at what I should replace methods like:
cvInRangeS and cvSmooth with?

[saudet]

The snapshots are not ready for all platforms. You'll have to wait tomorrow for that. We can refer to OpenCV's documentation for the equivalences.

[saudet]

The fix has now been released with JavaCV 1.4.4, enjoy! And thanks for reporting this issue.