opencv学习之路（4）、Mat类介绍，基本绘图函数

一、Mat类创建

    Mat img;//创建无初始化矩阵
    Mat img1(200,100,CV_8UC1);//200行，100列（长200，宽100）
    Mat img2(Size(200,100),CV_8UC3,Scalar(0,255,0));//长100，宽200
    Mat img3(200,100,CV_8UC3,Scalar(0,255,0));//创建200行，100列的8位三通道矩阵
    Mat img4(200,100,CV_8UC1,Scalar(255));//创建单通道矩阵    

#include <opencv2/opencv.hpp>
using namespace cv;

void main(){
    Mat img1=imread("E://1.jpg");
    Mat img2(img1);
    Mat img3=img1;
    Mat img4=img1.clone();
    Mat img5;
    img1.copyTo(img5);

    cvtColor(img1,img1,CV_BGR2HSV);//BGR图转为HSV图
    imshow("img1",img1);
    imshow("img2",img2);
    imshow("img3",img3);//image1/2/3跟随原图变化
    imshow("img4",img4);
    imshow("img5",img5);//image4/5不会跟随原图变化
    waitKey(0);
}

二、基本绘图函数

1、画线、画圆、画矩形

#include <opencv2/opencv.hpp>
using namespace cv;

void main(){
    Mat img(500,400,CV_8UC3,Scalar(255,255,255));//创建一个500行400列，3通道（即彩色图）的白色图
    line(img,Point(10,10),Point(100,250),Scalar(0,255,255),20,8);//在img图中画一条黄线，线宽为20，线型为8联通（一般都设置为8）
    circle(img,Point(200,100),50,Scalar(0,255,255),15,8);   //以（200,100）为圆心，半径为50，线宽为15画空心圆
    circle(img,Point(200,250),50,Scalar(0,255,255),-1,8);   //设置为-1时，画实心圆
    rectangle(img,Point(10,100),Point(200,200),Scalar(0,0,255),1,8);   //传入坐上、右下角坐标，画空心矩形
    rectangle(img,Rect(200,300,100,50),Scalar(0,255,0),-1,8); //传矩形数据（左上角坐标（200,300）和宽100，高50），画实心绿色矩形

    imshow("drawing",img);
    waitKey(0);
}

2、画椭圆、画多边形、写入文字

#include <opencv2/opencv.hpp>
using namespace cv;

void main(){
    Mat img(600,650,CV_8UC3,Scalar(255,255,255));
    ellipse(img,Point(200,200),Size(180,80),15,0,360,Scalar(0,255,255),10,8);   //画椭圆，（200,200）为中点，15旋转角度，0~360度，长轴180，短轴80
    ellipse(img,RotatedRect(Point(350,350),Size(150,100),40),Scalar(0,255,0),-1,8);   //画椭圆，40旋转角度
    
    Point ppt[]={Point(120,50),Point(180,50),Point(210,100),Point(180,150),Point(120,150),Point(90,100)};
    Point ppt2[]={Point(80,400),Point(80,550),Point(250,500),Point(300,550)};//定义点集
    const Point* pts[]={ppt};
    const Point* pts2[]={ppt2};
    int npt[]={6};
    int npt2[]={4};
    fillPoly(img,pts,npt,1,Scalar(255,255,0),8);   //画填充多边形
    polylines(img,pts2,npt2,1,false,Scalar(0,100,200),2,8);   //画多边形，false为不闭合，true为闭合
    
    putText(img,"China",Point(400,400),CV_FONT_BLACK,2,Scalar(100,100,100),5,8);//写入文字

    imshow("drawing",img);
    waitKey(0);
}