涉及到的绘制函数如下:
- 用于绘制直线的 line 函数;
- 用于绘制椭圆的 ellipse 函数;
- 用于绘制矩形的 rectangle 函数;
- 用于绘制圆的 circle 函数;
- 用于绘制填充的多边形的 fillPoly函数
这里我们通过一个OpenCV官方的示例程序来掌握OpenCV中各种绘制函数的用法。
此示例主要的脉络是定义了几个自定义的绘制函数,然后调用这些自定义的函数绘制出了两幅图——化学原子示例图和一幅组合图。
//---------------------------------【头文件、命名空间包含部分】----------------------------
// 描述:包含程序所使用的头文件和命名空间
//------------------------------------------------------------------------------------------------
#include <opencv2/core/core.hpp>
#include <opencv2/highgui/highgui.hpp>
using namespace cv;
//此程序对于OpenCV3版需要额外包含头文件:
#include <opencv2/imgproc/imgproc.hpp>
//-----------------------------------【宏定义部分】--------------------------------------------
// 描述:定义一些辅助宏
//------------------------------------------------------------------------------------------------
#define WINDOW_NAME1 "【绘制图1】" //为窗口标题定义的宏
#define WINDOW_NAME2 "【绘制图2】" //为窗口标题定义的宏
#define WINDOW_WIDTH 600//定义窗口大小的宏
//--------------------------------【全局函数声明部分】-------------------------------------
// 描述:全局函数声明
//-----------------------------------------------------------------------------------------------
void DrawEllipse( Mat img, double angle );//绘制椭圆
void DrawFilledCircle( Mat img, Point center );//绘制圆
void DrawPolygon( Mat img );//绘制多边形
void DrawLine( Mat img, Point start, Point end );//绘制线段
//-----------------------------------【ShowHelpText( )函数】----------------------------------
// 描述:输出一些帮助信息
//----------------------------------------------------------------------------------------------
void ShowHelpText()
{
//输出欢迎信息和OpenCV版本
printf("\n\n\t\t\t非常感谢购买《OpenCV3编程入门》一书!\n");
printf("\n\n\t\t\t此为本书OpenCV3版的第20个配套示例程序\n");
printf("\n\n\t\t\t 当前使用的OpenCV版本为:" CV_VERSION );
printf("\n\n ----------------------------------------------------------------------------\n");
}
//---------------------------------------【main( )函数】--------------------------------------
// 描述:控制台应用程序的入口函数,我们的程序从这里开始执行
//-----------------------------------------------------------------------------------------------
int main( void )
{
// 创建空白的Mat图像
Mat atomImage = Mat::zeros( WINDOW_WIDTH, WINDOW_WIDTH, CV_8UC3 );
Mat rookImage = Mat::zeros( WINDOW_WIDTH, WINDOW_WIDTH, CV_8UC3 );
ShowHelpText();
// ---------------------<1>绘制化学中的原子示例图------------------------
//【1.1】先绘制出椭圆
DrawEllipse( atomImage, 90 );
DrawEllipse( atomImage, 0 );
DrawEllipse( atomImage, 45 );
DrawEllipse( atomImage, -45 );
//【1.2】再绘制圆心
DrawFilledCircle( atomImage, Point( WINDOW_WIDTH/2, WINDOW_WIDTH/2) );
// ----------------------------<2>绘制组合图-----------------------------
//【2.1】先绘制出椭圆
DrawPolygon( rookImage );
// 【2.2】绘制矩形
rectangle( rookImage,
Point( 0, 7*WINDOW_WIDTH/8 ),
Point( WINDOW_WIDTH, WINDOW_WIDTH),
Scalar( 0, 255, 255 ),
-1,
8 );
// 【2.3】绘制一些线段
DrawLine( rookImage, Point( 0, 15*WINDOW_WIDTH/16 ), Point( WINDOW_WIDTH, 15*WINDOW_WIDTH/16 ) );
DrawLine( rookImage, Point( WINDOW_WIDTH/4, 7*WINDOW_WIDTH/8 ), Point( WINDOW_WIDTH/4, WINDOW_WIDTH ) );
DrawLine( rookImage, Point( WINDOW_WIDTH/2, 7*WINDOW_WIDTH/8 ), Point( WINDOW_WIDTH/2, WINDOW_WIDTH ) );
DrawLine( rookImage, Point( 3*WINDOW_WIDTH/4, 7*WINDOW_WIDTH/8 ), Point( 3*WINDOW_WIDTH/4, WINDOW_WIDTH ) );
// ---------------------------<3>显示绘制出的图像------------------------
imshow( WINDOW_NAME1, atomImage );
moveWindow( WINDOW_NAME1, 0, 200 );
imshow( WINDOW_NAME2, rookImage );
moveWindow( WINDOW_NAME2, WINDOW_WIDTH, 200 );
waitKey( 0 );
return(0);
}
其中,4个自定义的函数解析如下:
//-------------------------------【DrawEllipse( )函数】--------------------------------
// 描述:自定义的绘制函数,实现了绘制不同角度、相同尺寸的椭圆
//-----------------------------------------------------------------------------------------
// 函数DrawEllipse()调用了OpenCV中的ellipse函数,将椭圆画到图像img上,
// 椭圆中心为点( WINDOW_WIDTH/2.0, WINDOW_WIDTH/2.0),
// 并且大小位于矩形( WINDOW_WIDTH/4.0, WINDOW_WIDTH/16.0 )内。
// 椭圆旋转角度为angle,扩展的弧度从0度到360度。
// 图形颜色为Scalar(255,129,0)代表的蓝色,线宽(thickess)为2,线型(lineType)为 8 (8联通线型)。
//-----------------------------------------------------------------------------------------
void DrawEllipse( Mat img, double angle )
{
int thickness = 2;
int lineType = 8;
ellipse( img,
Point( WINDOW_WIDTH/2, WINDOW_WIDTH/2 ),
Size( WINDOW_WIDTH/4, WINDOW_WIDTH/16 ),
angle,
0,
360,
Scalar( 255, 129, 0 ),
thickness,
lineType );
}
//-----------------------------------【DrawFilledCircle( )函数】---------------------------
// 描述:自定义的绘制函数,实现了实心圆的绘制
//-----------------------------------------------------------------------------------------
// 函数DrawFilledCircle()调用了OpenCV 中的circle函数,将圆画到图像img上,
// 圆心由点 center 定义,圆的半径为WINDOW WIDTH/32,
// 圆的颜色为Scalar(0,0,255),按BGR的格式为红色,线粗定义为thickness = -1,因此绘制的圆是实心的。
//-----------------------------------------------------------------------------------------
void DrawFilledCircle( Mat img, Point center )
{
int thickness = -1;
int lineType = 8;
circle( img,
center,
WINDOW_WIDTH/32,
Scalar( 0, 0, 255 ),
thickness,
lineType );
}
//-----------------------------------【DrawPolygon( )函数】--------------------------
// 描述:自定义的绘制函数,实现了凹多边形的绘制
//--------------------------------------------------------------------------------------
// 函数DrawPolygon()调用了OpenCV中的 fillPoly 函数,用于将多边形画到图像img上,
// 其中多边形的顶点集为ppt,要绘制的多边形顶点数目为npt, 要绘制的多边形数量仅为1,
// 多边形的颜色定义为白色Scalar(255,255,255).
//--------------------------------------------------------------------------------------
void DrawPolygon( Mat img )
{
int lineType = 8;
//创建一些点
Point rookPoints[1][20];
rookPoints[0][0] = Point( WINDOW_WIDTH/4, 7*WINDOW_WIDTH/8 );
rookPoints[0][1] = Point( 3*WINDOW_WIDTH/4, 7*WINDOW_WIDTH/8 );
rookPoints[0][2] = Point( 3*WINDOW_WIDTH/4, 13*WINDOW_WIDTH/16 );
rookPoints[0][3] = Point( 11*WINDOW_WIDTH/16, 13*WINDOW_WIDTH/16 );
rookPoints[0][4] = Point( 19*WINDOW_WIDTH/32, 3*WINDOW_WIDTH/8 );
rookPoints[0][5] = Point( 3*WINDOW_WIDTH/4, 3*WINDOW_WIDTH/8 );
rookPoints[0][6] = Point( 3*WINDOW_WIDTH/4, WINDOW_WIDTH/8 );
rookPoints[0][7] = Point( 26*WINDOW_WIDTH/40, WINDOW_WIDTH/8 );
rookPoints[0][8] = Point( 26*WINDOW_WIDTH/40, WINDOW_WIDTH/4 );
rookPoints[0][9] = Point( 22*WINDOW_WIDTH/40, WINDOW_WIDTH/4 );
rookPoints[0][10] = Point( 22*WINDOW_WIDTH/40, WINDOW_WIDTH/8 );
rookPoints[0][11] = Point( 18*WINDOW_WIDTH/40, WINDOW_WIDTH/8 );
rookPoints[0][12] = Point( 18*WINDOW_WIDTH/40, WINDOW_WIDTH/4 );
rookPoints[0][13] = Point( 14*WINDOW_WIDTH/40, WINDOW_WIDTH/4 );
rookPoints[0][14] = Point( 14*WINDOW_WIDTH/40, WINDOW_WIDTH/8 );
rookPoints[0][15] = Point( WINDOW_WIDTH/4, WINDOW_WIDTH/8 );
rookPoints[0][16] = Point( WINDOW_WIDTH/4, 3*WINDOW_WIDTH/8 );
rookPoints[0][17] = Point( 13*WINDOW_WIDTH/32, 3*WINDOW_WIDTH/8 );
rookPoints[0][18] = Point( 5*WINDOW_WIDTH/16, 13*WINDOW_WIDTH/16 );
rookPoints[0][19] = Point( WINDOW_WIDTH/4, 13*WINDOW_WIDTH/16 );
const Point* ppt[1] = { rookPoints[0] };
int npt[] = { 20 };
fillPoly( img,
ppt,
npt,
1,
Scalar( 255, 255, 255 ),
lineType );
}
//-----------------------------------【DrawLine( )函数】--------------------------
// 描述:自定义的绘制函数,实现了线的绘制
//---------------------------------------------------------------------------------
// DrawLine()函数调用了OpenCV中的line函数,用于在图像img上画一条从点start到点end的直线段,
// 线的颜色为Scalar(0,0,0)代表的黑色,线的粗细thickness为2,且此线为8联通(lineType = 8)。
//---------------------------------------------------------------------------------
void DrawLine( Mat img, Point start, Point end )
{
int thickness = 2;
int lineType = 8;
line( img,
start,
end,
Scalar( 0, 0, 0 ),
thickness,
lineType );
}