Improving Opencv7 Image Processing (imgproc module) : Basic Drawing

https://docs.opencv.org/4.3.0/d3/d96/tutorial_basic_geometric_drawing.html

Goals

In this tutorial you will learn how to:

• Draw a line by using the OpenCV function line()
• Draw an ellipse by using the OpenCV function ellipse()
• Draw a rectangle by using the OpenCV function rectangle()
• Draw a circle by using the OpenCV function circle()
• Draw a filled polygon by using the OpenCV function fillPoly()

OpenCV Theory

For this tutorial, we will heavily use two structures: cv::Point and cv::Scalar :

#include <opencv2/core/core.hpp>
#include<opencv2/imgproc/imgproc.hpp>
#include <opencv2/highgui/highgui.hpp>
#define w 400
using namespace cv;


void MyEllipse(Mat img, double angle);
void MyFilledCircle(Mat img, Point center);
void MyPolygon(Mat img);
void MyLine(Mat img, Point start, Point end);


int main(void){
	char atom_window[] = "Drawing 1: Atom";
	char rook_window[] = "Drawing 2: Rook";
	Mat atom_image = Mat::zeros(w, w, CV_8UC3);
	Mat rook_image = Mat::zeros(w, w, CV_8UC3);

	MyEllipse(atom_image, 90);
	MyEllipse(atom_image, 0);
	MyEllipse(atom_image, 45);
	MyEllipse(atom_image, -45);

	MyFilledCircle(atom_image, Point(w / 2, w / 2));
	MyPolygon(rook_image);
	rectangle(rook_image,
		Point(0, 7 * w / 8),
		Point(w, w),
		Scalar(0, 255, 255));

	MyLine(rook_image, Point(0, 15 * w / 16), Point(w, 15 * w / 16));
	MyLine(rook_image, Point(w / 4, 7 * w / 8), Point(w / 4, w));
	MyLine(rook_image, Point(w / 2, 7 * w / 8), Point(w / 2, w));
	MyLine(rook_image, Point(3 * w / 4, 7 * w / 8), Point(3 * w / 4, w));

	imshow(atom_window, atom_image);
	moveWindow(atom_window, 0, 200);
	imshow(rook_window, rook_image);
	moveWindow(rook_window, w, 200);
	waitKey(0);
	return(0);
}
void MyEllipse(Mat img, double angle)
{
	int thickness = 2;
	int lineType = 8;
	ellipse(img,
		Point(w / 2, w / 2),
		Size(w / 4, w / 16),
		angle,
		0,
		360,
		Scalar(255, 0, 0),
		thickness,
		lineType);
}
void MyFilledCircle(Mat img, Point center)
{
	circle(img,
		center,
		w / 32,
		Scalar(0, 0, 255), -1);
}
void MyPolygon(Mat img)
{
	int lineType = 8;
	Point rook_points[1][20];
	rook_points[0][0] = Point(w / 4, 7 * w / 8);
	rook_points[0][1] = Point(3 * w / 4, 7 * w / 8);
	rook_points[0][2] = Point(3 * w / 4, 13 * w / 16);
	rook_points[0][3] = Point(11 * w / 16, 13 * w / 16);
	rook_points[0][4] = Point(19 * w / 32, 3 * w / 8);
	rook_points[0][5] = Point(3 * w / 4, 3 * w / 8);
	rook_points[0][6] = Point(3 * w / 4, w / 8);
	rook_points[0][7] = Point(26 * w / 40, w / 8);
	rook_points[0][8] = Point(26 * w / 40, w / 4);
	rook_points[0][9] = Point(22 * w / 40, w / 4);
	rook_points[0][10] = Point(22 * w / 40, w / 8);
	rook_points[0][11] = Point(18 * w / 40, w / 8);
	rook_points[0][12] = Point(18 * w / 40, w / 4);
	rook_points[0][13] = Point(14 * w / 40, w / 4);
	rook_points[0][14] = Point(14 * w / 40, w / 8);
	rook_points[0][15] = Point(w / 4, w / 8);
	rook_points[0][16] = Point(w / 4, 3 * w / 8);
	rook_points[0][17] = Point(13 * w / 32, 3 * w / 8);
	rook_points[0][18] = Point(5 * w / 16, 13 * w / 16);
	rook_points[0][19] = Point(w / 4, 13 * w / 16);
	const Point* ppt[1] = { rook_points[0] };
	int npt[] = { 20 };
	fillPoly(img,
		ppt,
		npt,
		1,
		Scalar(255, 255, 255),
		lineType);
}
void MyLine(Mat img, Point start, Point end)
{
	int thickness = 2;
	int lineType = 8;
	line(img,
		start,
		end,
		Scalar(0, 0, 0),
		thickness,
		lineType);
}