学步园

一、绘图操作---画抛物线

void parabola(IplImage *image, CvPoint pL, CvPoint pM, CvPoint pR, const CvScalar &color, int thickness)
{
     double x1, y1, x2, y2, x3, y3, a, b, c;
     x1 = (double)pL.x;
     y1 = (double)pL.y;
     x2 = (double)pM.x;
     y2 = (double)pM.y;
     x3 = (double)pR.x;
     y3 = (double)pR.y;
     a = ((y1-y2)/(x1-x2)-(y1-y3)/(x1-x3)) / (x2-x3);
     b = (y1-y2)/(x1-x2)-a*(x1+x2);
     c = y1-a*x1*x1-b*x1;
     //x的变化范围是[x1, x3],三像素画一个点
     int x = 0;
    double y = 0;
     vector<CvPoint> pt;
     for (x = int(x1); x <= int(x3); x = x+3)
    {
         y = a * double(x) * double(x) + b * double(x) + c;
         pt.push_back(cvPoint(x, int(y)));
     }
     pt.push_back(cvPoint(int(x3), int(y3)));
     for (size_t i = 0; i < pt.size()-1; ++ i)
     {
        cvLine(image, pt[i], pt[i+1], color);
     }
}

二.绘图操作-画圆

#include "cv.h"  
#include "highgui.h"  
#include <stdio.h>  
#include <../opencv2/core/core.hpp>


using namespace std;
using namespace cv;

int main(int argc,char **argv)  
{  
	//圆心
	Point center = Point(255,255);
	//半径
	int r = 100;
	//承载图像
	Mat picture(500,500,CV_8UC3,Scalar(255,255,255));
	//参数为：承载的图像、圆心、半径、颜色、粗细、线型
	circle(picture,center,r,Scalar(0,0,0),-1);
	imshow("底板",picture);
    waitKey(0);

}  

效果如图所示：

其中可以通过把线的粗细设置为-1来画实心的图形