Java Opencv Mat constructor mismatch

Question

I am trying to create a Mat object as follows:

// ROI by creating mask for the trapezoid
Mat mask = Mat(frame.rows(), frame.cols(), CvType.CV_8UC1, new Scalar(0));

However I get the following compile-time error:

The method Mat(int, int, int, Scalar) is undefined for the type

Whereas in Mat.class file I can surely see the following function signature:

//
// C++: Mat::Mat(int rows, int cols, int type, Scalar s)
//

// javadoc: Mat::Mat(rows, cols, type, s)
public Mat(int rows, int cols, int type, Scalar s)
{

    nativeObj = n_Mat(rows, cols, type, s.val[0], s.val[1], s.val[2], s.val[3]);

    return;
}

Is this a bug, or?

shouldn't it be Mat mask = new Mat(...) in the first place? — Miki
– Miki, Commented Nov 14, 2016 at 11:45
You are right, stupid of me, I am converting the code from C++ to Java, hence the mistake. I'll accept it as answer if you write it. Thanks. — Schütze
– Schütze, Commented Nov 14, 2016 at 11:59

Miki · Accepted Answer · 2016-11-14 12:01:17Z

1

The signature is correct. In Java you need to use the new keyword to create new objects:

Mat mask = new Mat(frame.rows(), frame.cols(), CvType.CV_8UC1, new Scalar(0));

answered Nov 14, 2016 at 12:01

Miki

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