知识点

1、使用cv::Point(代表点)，cv::Scalar(代表颜色向量)；
2、绘制线，矩形，圆，椭圆等基本几何形状；
3、随机生成与（图像上）绘制文本；
4、代码演示；

使用cv::Point与cv::Scalar

1、Point表示2D平面上一个点x,y;

//use
Point p;
p.x = 10;
p.y = 8;
or
p = Point(10,8);

2、Scalar表示四个元素的向量（Scalar最多只能传入4个参数）

	Scalar(a,b,c);//a = blue;b = green;c = red表示RGB的3个通道

绘制线，矩形，圆，椭圆

1. 画线：cv::line;
   line()中有个参数：linetype：LINE_4\LINE_8\LINE_AA(反锯齿)；
2. 画椭圆：cv::eliipse();
3. 画矩形：cv::rectangle();
4. 画圆：cv::circle;
5. 画填充：cv::fillPoly;
6. 写字：putText();

使用随机数

使用RNG类生成随机数，传入种子12345，方法uniform限定在规定范围内生成随机数；

void RandomLineDemo()
{
   
	RNG rng(12345);//12345为种子
	Point pt1;
	Point pt2;
	Mat bg = Mat::zeros(bgImage.size(), bgImage.type());
	namedWindow("random line window", CV_WINDOW_AUTOSIZE);
	for (int i = 0; i < 100000; i++)
	{
   
	pt1.x = rng.uniform(0, bgImage.cols); //在规定范围内
	pt2.x = rng.uniform(0, bgImage.cols);
	pt1.y = rng.uniform(0, bgImage.rows);
	pt2.y = rng.uniform(0, bgImage.rows);
	Scalar color = Scalar(rng.uniform(0, 255), rng.uniform(0, 255), rng.uniform(0, 255)); //生成规定范围内的颜色
	if (waitKey(50) > 0)
	{
   
		break;
	}
	line(bg, pt1, pt2, color, 1, LINE_8);
	imshow("random line window", bg);
	}

}

Demo

#include <opencv2/opencv.hpp>
#include <iostream>

using namespace std;
using namespace cv;

Mat bgImage;
const char* drawdemo_win = "draw shapes and text demo";

void MyLines();
void MyRectangle();
void MyEllipse();
void MyCircle();
void MyPolygon();
void RandomLineDemo();
int main(int argc, char** argv)
{
   
	bgImage = imread("C:\\Users\\hello\\Desktop\\bai.jpg");
	if (!bgImage.data)
	{
   
		cout << "could not load the image..." << endl;
		return -1;
	}
	MyLines();
	MyRectangle();
	MyEllipse();
	MyCircle();
	MyPolygon();
	//绘制文字 （fontScale）字体大小 thickness: 粗细
	putText(bgImage, "Hello OpenCV", Point(300, 300), CV_FONT_HERSHEY_COMPLEX, 1.0, Scalar(12, 23, 200),2, LINE_8);
	namedWindow(drawdemo_win, CV_WINDOW_AUTOSIZE);
	imshow(drawdemo_win, bgImage);
	RandomLineDemo();
	

	waitKey(0);
	return 0;
}

void MyLines()
{
   
	Point p1 = Point(20, 30);
	Point p2;
	p2.x = 300;
	p2.y = 300;
	Scalar color = Scalar(0, 0, 255);//红色
	line(bgImage, p1, p2, color, 1, LINE_AA);  //画线,锯齿形
}
void MyRectangle()
{
   
	Rect rect = Rect(200, 100, 300, 300);
	Scalar color = Scalar(255, 0, 0);//blue
	rectangle(bgImage, rect, color, 2, LINE_8);

}
void MyEllipse()
{
   
	Scalar color = Scalar(0, 255, 0);
	//中心点，大小，朝那个方向，画的部分，线宽，线型
	ellipse(bgImage, Point(bgImage.cols / 2, bgImage.rows / 2),Size(bgImage.cols/4,bgImage.rows/8),90,0,360,color, 2, LINE_8);
}
void MyCircle()
{
   
	Scalar color = Scalar(0, 255, 255);
	circle(bgImage, Point(bgImage.cols / 2, bgImage.rows / 2), 150, color, 2, LINE_4);
}
void MyPolygon()   //填充图形
{
   
	//定义一个二维Point，，声明二维坐标指针
	Point pts[1][5];
	pts[0][0] = Point(100, 100);
	pts[0][1] = Point(100, 200);
	pts[0][2] = Point(200, 200);
	pts[0][3] = Point(200, 100);
	pts[0][4] = Point(100, 100);
	
	const Point* ppts[] = {
    pts[0] };
	int npt[] = {
    5 };
	Scalar color = Scalar(255, 12, 255);
	
	fillPoly(bgImage, ppts, npt, 1, color, LINE_8);

}
void RandomLineDemo()
{
   
	RNG rng(12345);//12345为种子
	Point pt1;
	Point pt2;
	Mat bg = Mat::zeros(bgImage.size(), bgImage.type());
	namedWindow("random line window", CV_WINDOW_AUTOSIZE);
	for (int i = 0; i < 100000; i++)
	{
   
	pt1.x = rng.uniform(0, bgImage.cols); //在规定范围内
	pt2.x = rng.uniform(0, bgImage.cols);
	pt1.y = rng.uniform(0, bgImage.rows);
	pt2.y = rng.uniform(0, bgImage.rows);
	Scalar color = Scalar(rng.uniform(0, 255), rng.uniform(0, 255), rng.uniform(0, 255)); //生成规定范围内的颜色
	if (waitKey(50) > 0)
	{
   
		break;
	}
	line(bg, pt1, pt2, color, 1, LINE_8);
	imshow("random line window", bg);
	}

}

运行效果