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Android: Why can't I initialize BackgroundSubtractor with Video.createBackgroundSubtractorMOG2()?

asked 2019-03-27 08:51:10 -0500

I implemented my class with CameraBridgeViewBase.CvCameraViewListener2. And here is my onCameraFrame() method that does the processing after frame grabbing before rendering the frame on screen:

public Mat onCameraFrame(CameraBridgeViewBase.CvCameraViewFrame inputFrame) {
    Mat frame=(Mat)inputFrame;
    Mat fgMask=new Mat();
    BackgroundSubtractor bs=Video.createBackgroundSubtractorMOG2();
    //return 4 channel as rgba or 1 channel as gray scale
    return inputFrame.rgba();

I learn the syntax from here.

The problem is that Android Studio says 'Cannot resolve method createBackgroundSubtractorMOG2()' after I imported the Video class.

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code runs fine on desktop java, so the problem unfortunately is between you and your ide (and there's not much we can do from here) ;(

apart from that,you have another problem: it does not make any sense, to create a new bgsubtractor per frame (onCameraFrame is the wrong place to create one).

berak gravatar imageberak ( 2019-03-28 00:46:06 -0500 )edit

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answered 2019-03-29 11:24:44 -0500

I did it in onCameraFrame():

    public Mat onCameraFrame(CameraBridgeViewBase.CvCameraViewFrame inputFrame) {
    mRgba = inputFrame.rgba();
    Imgproc.cvtColor(mRgba, mRgb, Imgproc.COLOR_RGBA2RGB); //the apply function will throw the above error if you don't feed it an RGB image
    sub.apply(mRgb, mFGMask, -1); //apply() exports a gray image by definition
    Imgproc.cvtColor(mFGMask, mRgba, Imgproc.COLOR_GRAY2RGBA);

    return mRgba;

The global vars needed:

 private BackgroundSubtractorMOG2 sub = new BackgroundSubtractorMOG2(10, 25, false);
private Mat mRgb=new Mat();
private Mat mFGMask=new Mat();
private Mat mRgba=new Mat();

Credits to Austin from Stack Overflow.

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Asked: 2019-03-27 08:51:10 -0500

Seen: 252 times

Last updated: Mar 29 '19