OpenCV3学习笔记（8）：基本绘图

参考文档：https://docs.opencv.org/3.4.11/d6/d6e/group__imgproc__draw.html

参考教程：https://www.w3cschool.cn/opencv/opencv-fpo82ccc.html

0.准备工作

Point 表示一个2D坐标点

Point pt;
pt.x = 10;
pt.y = 8;

Point pt=Point(10,8);

Rect 表示一个矩形区域

Rect rect=Rect(0,0,100,100); //左上角xy+长宽

Size 表示大小

Size size=Size(100,100);

Scalar 可用来表示颜色，分别为BGRA分量

Scalar(1,2,3);  //blue=1,green=2,red=3

1.画圆 circle

void cv::circle	(	
    InputOutputArray img, //图像
    Point center,         //原心位置
    int radius,           //半径大小
    const Scalar & color, //颜色
    int thickness = 1,    //画笔粗细，负值则为实心填充
    int lineType = LINE_8,//线类型枚举LineTypes，LINE_AA抗锯齿
    int shift = 0         //中心坐标和半径值中的小数位数
)	

测试代码： 

	circle(canvas, Point(100, 100), 50,Scalar(255,255,255) , -1);
	circle(canvas, Point(100, 100), 60, Scalar(255, 255, 255), 2);

2.画直线

void cv::line(	
    InputOutputArray img,  //图像
    Point pt1,             //起点
    Point pt2,             //终点
    const Scalar & color,  //颜色
    int thickness = 1,     //线宽，粗细
    int lineType = LINE_8, //线类型枚举LineTypes，LINE_AA抗锯齿
    int shift = 0          //点坐标中的小数位数
)	

测试代码：

line(canvas, Point(100, 100), Point(500, 100), Scalar(255, 255, 0), 2);

3.画椭圆ellipse

void cv::ellipse(	
    InputOutputArray img,    //图像
    const RotatedRect & box, //外接矩形
    const Scalar & color,    //颜色
    int thickness = 1,       //画笔粗细，负值则为实心填充
    int lineType = LINE_8    //线类型枚举LineTypes，LINE_AA抗锯齿
)	


void cv::ellipse(	
    InputOutputArray img, //图像
    Point center,         //圆心
    Size axes,            //主轴尺寸的一半
    double angle,         //旋转角度，单位为角度
    double startAngle,    //其实角
    double endAngle,      //终止角
    const Scalar & color, //颜色
    int thickness = 1,    //画笔粗细，负值则为实心填充
    int lineType = LINE_8,//线类型枚举LineTypes，LINE_AA抗锯齿
    int shift = 0         //中心坐标和轴值的小数位数
)	

测试代码：

	ellipse(canvas, Point(100, 300), Size(100, 50),0,0,360,Scalar(0, 0, 255), -1);
	ellipse(canvas, Point(100, 300), Size(80, 40), 0, 0, 120, Scalar(0, 255, 0), -1);
	ellipse(canvas, Point(100, 300), Size(50, 100), 0, 0, 360, Scalar(255, 0, 0), 2);

4.画矩形rectangle

void cv::rectangle(	
    InputOutputArray img, //图像
    Point pt1,            //矩形顶点1
    Point pt2,            //顶点1对角线上的顶点2
    const Scalar & color, //颜色
    int thickness = 1,    //画笔粗细，负值则为实心填充
    int lineType = LINE_8,//线类型枚举LineTypes，LINE_AA抗锯齿
    int shift = 0         //点坐标中的小数位数
)	

void cv::rectangle(	
    Mat & img,             //图像
    Rect rec,              //矩形（左上角顶点+size）
    const Scalar & color,  //颜色
    int thickness = 1,     //画笔粗细，负值则为实心填充
    int lineType = LINE_8, //线类型枚举LineTypes，LINE_AA抗锯齿
    int shift = 0          //点坐标中的小数位数
)	

测试代码：

	rectangle(canvas, Point(50,475),Point(150,525),Scalar(0,0,255),-1);
	//rectangle(canvas, Point(75, 450), Point(125, 550), Scalar(0, 255, 0), 2);
	rectangle(canvas, Rect(75,450,50,100), Scalar(0, 255, 0), 2);

5.画多边形fillPoly

void cv::fillPoly(	
    Mat & img,             //图像
    const Point ** pts,    //多边形顶点数组
    const int * npts,      //每个数组中顶点个数
    int ncontours,         //多少个顶点数组
    const Scalar & color,  //颜色
    int lineType = LINE_8, //线类型枚举LineTypes，LINE_AA抗锯齿
    int shift = 0,         //顶点坐标中的小数位数
    Point offset = Point() //轮廓所有点的可选偏移量
)	

void cv::fillPoly(	
    InputOutputArray img,   //图像
    InputArrayOfArrays pts, //多边形点数组
    const Scalar & color,   //颜色
    int lineType = LINE_8,  //线类型枚举LineTypes，LINE_AA抗锯齿
    int shift = 0,          //顶点坐标中的小数位数
    Point offset = Point()  //轮廓所有点的可选偏移量
)	

测试代码：

	Point pts_1[3] = {Point(300,300),Point(300,350),Point(350,350)};
	Point pts_2[4] = { Point(300,400),Point(300,450),Point(400,500),Point(500,420) };
	const Point* pts_list[] = { pts_1,pts_2 };
	const int pts_size[] = { 3,4 };
	fillPoly(canvas, pts_list, pts_size, 2, Scalar(0, 255, 255));

6.绘制文字putText（英文）

void cv::putText(	
    InputOutputArray img,  //图像
    const String & text,   //字符串
    Point org,             //文本左下角坐标
    int fontFace,          //字体类型枚举HersheyFonts
    double fontScale,      //字体比例因子乘以特定于字体的基本大小
    Scalar color,          //颜色
    int thickness = 1,     //粗细
    int lineType = LINE_8, //线类型枚举LineTypes，LINE_AA抗锯齿
    bool bottomLeftOrigin = false  //如果为true，则图像数据原点位于左下角。否则，它位于左上角
)	

测试代码：

putText(canvas, "OpenCV", Point(250, 80), FONT_HERSHEY_SIMPLEX, 1, Scalar(255, 255, 0), 2);

7.完整代码

#include 
#include 

using namespace cv;

int main()
{
	//创建一个全0的黑色图作为画布
	Mat canvas= Mat::ones(Size(600, 600), CV_8UC3);

	//绘制圆形
	circle(canvas, Point(100, 100), 50,Scalar(255,255,255) , -1);
	circle(canvas, Point(100, 100), 60, Scalar(255, 255, 255), 2);

	//绘制直线
	line(canvas, Point(100, 100), Point(500, 100), Scalar(255, 255, 0), 2);

	//画椭圆
	ellipse(canvas, Point(100, 300), Size(100, 50),0,0,360,Scalar(0, 0, 255), -1);
	ellipse(canvas, Point(100, 300), Size(80, 40), 0, 0, 120, Scalar(0, 255, 0), -1);
	ellipse(canvas, Point(100, 300), Size(50, 100), 0, 0, 360, Scalar(255, 0, 0), 2);

	//画矩形
	rectangle(canvas, Point(50,475),Point(150,525),Scalar(0,0,255),-1);
	//rectangle(canvas, Point(75, 450), Point(125, 550), Scalar(0, 255, 0), 2);
	rectangle(canvas, Rect(75,450,50,100), Scalar(0, 255, 0), 2);

	//画多边形
	Point pts_1[3] = {Point(300,300),Point(300,350),Point(350,350)};
	Point pts_2[4] = { Point(300,400),Point(300,450),Point(400,500),Point(500,420) };
	const Point* pts_list[] = { pts_1,pts_2 };
	const int pts_size[] = { 3,4 };
	fillPoly(canvas, pts_list, pts_size, 2, Scalar(0, 255, 255));

	//画文字（英文）
	putText(canvas, "OpenCV", Point(250, 80), FONT_HERSHEY_SIMPLEX, 1, Scalar(255, 255, 0), 2);

	imshow("canvas", canvas);
	waitKey(0);
	return 0;
}