Catalog

1. Color conversion cvtcolor De background

 2. Image rendering

 3. random number

4. Polygon drawing

1. Color conversion cvtcolor De background

//hsv Space by  hs control , If the background color is single , You should use hsv To control the 
	Mat hsv;
	cvtColor(image, hsv, COLOR_BGR2HSV);
	Mat mask;
	// Intercept the area of a specific pixel value 
	inRange(hsv, Scalar(35, 43, 46), Scalar(77, 255, 255), mask);

	Mat redback = Mat::zeros(image.size(), image.type());
	redback = Scalar(40, 40, 200);
	// Yes mask Take the opposite 
	bitwise_not(mask, mask);
	imshow("mask", mask);
	// Copy only mask by 1 Region 
	image.copyTo(redback, mask);
	imshow("roi Region extraction ", redback);

 2. Image rendering

// rectangular 
	Rect rect;
	// Initial coordinates  
	rect.x = 100;
	rect.y = 100;
	// Rectangle size 
	rect.width = 250;
	rect.height = 300;
	Mat bg = Mat::zeros(image.size(), image.type());
	// Draw a rectangle   The fourth parameter is less than 0 That is, the filling is greater than 0 It's linewidth  8 Is Linetype （ Default ·）
	rectangle(bg, rect, Scalar(0, 0, 255), -1, 8, 0);
	// Draw the circle   center of a circle Point(350, 400)  radius ：15  Color control ：Scalar(255, 0, 0)b g r
	circle(bg, Point(350, 400), 15, Scalar(255, 0, 0), -1, 8, 0);
	// Draw the line 
	line(bg, Point(100, 100), Point(350, 400), Scalar(0, 255, 0), 4, LINE_AA, 0);
	// Rotate rectangle （RotatedRect）
	RotatedRect rrt;
	rrt.center = Point(200, 200);
	rrt.size = Size(100, 200);
	rrt.angle = 90.0;
	// The ellipse 
	ellipse(bg, rrt, Scalar(0, 255, 255), 2, 8);
	Mat dst;
	// Image addition 
	beta, double gamma, CvArr* dst );
	/*
	     Parameters 1：src1, The first original array .
		 Parameters 2：alpha, The weight of the first array element 

		 Parameters 3：src2 The second original array 
		 Parameters 4：beta, The weight of the second array element 
		 Parameters 5：gamma, chart 1 And graph 2 The value added after and . Don't be too big , Otherwise the picture will be white . The sum is equal to 255 The above is pure white .

		 Parameters 6：dst, Output pictures 
	*/
	addWeighted(image, 0.7, bg, 0.3, 0, dst);
	imshow(" Draw a demo ", bg);

 3. random number

Mat canvas = Mat::zeros(Size(512, 512), CV_8UC3);
	int w = canvas.cols;
	int h = canvas.rows;
	// Random seeds 
	RNG rng(12345);
	while (true) {
		int c = waitKey(10);
		if (c == 27) { //  sign out 
			break;
		}
		// produce 0-w The data of 
		int x1 = rng.uniform(0, w);
		int y1 = rng.uniform(0, h);
		int x2 = rng.uniform(0, w);
		int y2 = rng.uniform(0, h);
		int b = rng.uniform(0, 255);
		int g = rng.uniform(0, 255);
		int r = rng.uniform(0, 255);
		// canvas = Scalar(0, 0, 0);
		line(canvas, Point(x1, y1), Point(x2, y2), Scalar(b, g, r), 1, LINE_AA, 0);
		imshow(" Random drawing demonstration ", canvas);
	}

4. Polygon drawing

// Definition point , Stored in an array , Store this array in another array to become a two-dimensional array , Drawing  

// canvas 
	Mat canvas = Mat::zeros(Size(512, 512), CV_8UC3);
	int w = canvas.cols;
	int h = canvas.rows;
	Point p1(100, 100);
	Point p2(300, 150);
	Point p3(300, 350);
	Point p4(250, 450);
	Point p5(50, 450);
	std::vector<Point> pts;
	pts.push_back(p1);
	pts.push_back(p2);
	pts.push_back(p3);
	pts.push_back(p3);
	pts.push_back(p4);
	pts.push_back(p5);
	//-1 Cannot be filled 
	// polylines(canvas, pts, true, Scalar(0, 255, 0), -1, 8, 0); // Draw polygon 
	//

	std::vector<std::vector<Point>> contours;
	contours.push_back(pts);
	// You can draw multiple polygons   Draw fill  -1
	drawContours(canvas, contours, 0, Scalar(0, 0, 255), -1, 8);
	imshow(" Draw polygon ", canvas);