opencv

point2f(y,x) # inverted!
BGR 	#not rgb ...
Scalar = 4 element vector
CV_RGB(r, g, b) #from bgs

Types:
	#depth
	CV_8U 	unsigned char
	CV_8S 	char
	CV_16U 	unsigned short
	CV_16S 	short
	CV_32S 	int
	CV_32F 	float
	CV_64F 	double
	# + channels C1..4 	eg RGBA:
	# eg Mat M(2,2, CV_8UC3, Scalar(0,0,255));
	0 to 255 for CV_8U images
	0 to 65535 for CV_16U images
	0 to 1 for CV_32F images



Camera Calibration:
	distortion_coefficients - 5 values
	camera_matrix - 3x3 matrix - eg focal length etc.

	different methods:
		https://docs.opencv.org/4.x/d7/d21/tutorial_interactive_calibration.html
		https://docs.opencv.org/4.x/d6/d55/tutorial_table_of_content_calib3d.html

		# using chess board, to get values
		https://github.com/abidrahmank/OpenCV2-Python-Tutorials/blob/master/source/py_tutorials/py_calib3d/py_calibration/py_calibration.rs


roi - region of interest
	x, y, w, h

	// roi as subset of full data image
	Mat D (A, Rect(10, 10, 100, 100) ); // using a rectangle
	Mat E = A(Range::all(), Range(1,3)); // using row and column boundaries

Matrix
	Fill matrix with random values
		Mat R = Mat(3, 2, CV_8UC3);
		randu(R, Scalar::all(0), Scalar::all(255));

	Formatted output
		cout << "R (csv)     = " << endl << format(R, Formatter::FMT_CSV   ) << endl << endl;
		#sa FMT_C/PYTHON/NUMPY/CSV

MISC
	glob( dir, file )
	CommandLineParser
	randu() # https://docs.opencv.org/4.x/d2/de8/group__core__array.html#ga1ba1026dca0807b27057ba6a49d258c0
	cvtColor(img, img, COLOR_BGR2Luv); #convert color


BS:
https://docs.opencv.org/4.x/da/d5c/tutorial_canny_detector.html
https://docs.opencv.org/4.x/d1/dc5/tutorial_background_subtraction.html
https://web.archive.org/web/20140418093037/http://bmc.univ-bpclermont.fr/
https://web.archive.org/web/20140221195750/http://docs.opencv.org/trunk/doc/tutorials/video/background_subtraction/background_subtraction.html
https://www.pyimagesearch.com/2020/07/27/opencv-grabcut-foreground-segmentation-and-extraction/
https://learnopencv.com/applications-of-foreground-background-separation-with-semantic-segmentation/
https://docs.opencv.org/4.x/d2/d55/group__bgsegm.html
https://docs.opencv.org/4.x/d5/de8/samples_2cpp_2segment_objects_8cpp-example.html#_a15

tuts:))
https://docs.opencv.org/4.x/d6/d00/tutorial_py_root.html
https://datahacker.rs/opencv-thresholding/

# median frame as bg + frame difference
https://learnopencv.com/simple-background-estimation-in-videos-using-opencv-c-python/

https://learnopencv.com/contour-detection-using-opencv-python-c/
https://learnopencv.com/deep-learning-with-opencvs-dnn-module-a-definitive-guide/

moments
https://docs.opencv.org/4.x/d0/d49/tutorial_moments.html