The Core Functionality7(Basic Drawing)

Goals

In this tutorial you will learn how to:

Draw a line by using the OpenCV function line()(直线)
Draw an ellipse by using the OpenCV function ellipse()（椭圆）
Draw a rectangle by using the OpenCV function recctangel()(矩形)
Draw a circle by using the OpenCV function circle()(圆)
Draw a filled polygon by using the OpenCV function fillPoly()（填充多边形）

Point（点）

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

或者：Point pt=Point(10,8)

Scalar

代表一个4元素的向量。标量类型广泛用于OpenCV传递像素值。
在本教程中，我们将广泛使用它来表示BGR颜色值（3个参数）。如果不使用最后一个参数，则没有必要定义它。
让我们来看一个例子，如果我们要求一个颜色参数，并且我们给：

Scalar（a，b，c）

我们将定义BGR颜色，例如：蓝色= a，绿色= b和红色= c

Code

#include <opencv2/core.hpp>
#include <opencv2/imgproc.hpp>
#include <opencv2/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"; //图像1
char rook_window[] = "Drawing 2: Rook"; //图像2
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 );

//图像，相对顶点1和2，颜色，填充，线型
rectangle( rook_image,
Point( 0, 7*w/8 ),
Point( w, w),
Scalar( 0, 255, 255 ),
FILLED,
LINE_8 );

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;
//图像，中心点，长短轴，角度，范围，颜色，线宽，线型
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 )
{
//图像，中心，半径，颜色，FILLLED（-1）,LINE_8(8连通线型)
circle( img,
center,
w/32,
Scalar( 0, 0, 255 ),
FILLED,
LINE_8 );
}
void MyPolygon( Mat img )
{
int lineType = LINE_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] }; //说明数组的每个元素均为指针，而这个指针为顶点集合的首元素开始地址
int npt[] = { 20 }; //指针
//图像，顶点集（指针的指针），边（指针的指针），数量，颜色，线型
fillPoly( img,
ppt,
npt,
1,
Scalar( 255, 255, 255 ),
lineType );
}
void MyLine( Mat img, Point start, Point end )
{
int thickness = 2;
int lineType = LINE_8;
//图像，开始，结束，颜色，线宽，线型
line( img,
start,
end,
Scalar( 0, 0, 0 ),
thickness,
lineType );

}

CMakeLists.txt文件如下：

cmake_minimum_required(VERSION 2.8)
set(CMAKE_CXX_FLAGS "-std=c++11")
project( DisplayImage )
find_package( OpenCV REQUIRED )
include_directories( ${OpenCV_INCLUDE_DIRS} )
add_executable( DisplayImage main.cpp )
target_link_libraries( DisplayImage ${OpenCV_LIBS} )

install(TARGETS DisplayImage RUNTIME DESTINATION bin)

运行结果如下：