Assertion failed (m.dims >= 2) at erode

Hi,

I was trying to run the code of the grabFrame method from the ObjRecognitionController class but I'm getting an error when I perform the Imgproc.erode operation:

Mat erodeElement = Imgproc.getStructuringElement(Imgproc.MORPH_RECT, new Size(12, 12));
Imgproc.erode(mask, morphOutput, erodeElement);

The error is:

OpenCV Error: Assertion failed (m.dims >= 2) in cv::Mat::Mat, file C:\builds\master_PackSlaveAddon-win64-vc12-static\opencv\modules\core\src\matrix.cpp, line 454
Exception in thread "main" CvException [org.opencv.core.CvException: cv::Exception: C:\builds\master_PackSlaveAddon-win64-vc12-static\opencv\modules\core\src\matrix.cpp:454: error: (-215) m.dims >= 2 in function cv::Mat::Mat
]
at org.opencv.imgproc.Imgproc.erode_2(Native Method)
at org.opencv.imgproc.Imgproc.erode(Imgproc.java:2007)
at MainMorphological.main(MainMorphological.java:34)

Have you had to deal with this error?do you know what the reason of the error is?

I don't know what the problem is since the mask and morphOutput elements are empty Mats and the erodeElement is exactly the same as the one you're using.

Thanks in advance.

[luigidr]

Hi,

I never encountered this error before... I can verify the code in the next days. eroWhat version of OpenCV (and Java) are you running? In which version of Windows are you working?

Notice, however, that mask should not be an empty Mat. In the ObjRecognitionController class, mask is filled by the code at line 203:

// threshold HSV image to select tennis balls
Core.inRange(hsvImage, minValues, maxValues, mask);

mask is the source image on which erode() works, it cannot be an "empty image".

Hi,

You are right, my problem was that the mask was an empty image. Since I was running a test and took only some pieces of your example I forgot to fill the mask. Now it's working fine.

Thanks a lot for your time.