opencv拟合抛物线

简介

　　本篇主要是对opnecv函数cvSolve的熟悉笔记。这里只是简单用它来拟合抛物线。
大致内容为：预先设定三个点，用这三个点来拟合出它们的抛物线。

具体实现

实现代码

#include <opencv2/opencv.hpp>
#include <stdio.h>
using namespace cv;
using namespace std;
 
#define pointNUmber 3
 
Mat src;
CvPoint point[pointNUmber];
int width, height;
int pointAddr[pointNUmber][2] = {{70, 420}, {160, 90}, {390, 410}};
 
float A[3][3] = {{70*70, 70, 1}, {160*160, 160, 1}, {390*390, 390, 1}};
float B[3] = {420, 90, 410};
float C[3] = {0, 0, 0};
 
CvMat* matA = cvCreateMat(3,3,CV_32FC1); 
CvMat* matB = cvCreateMat(3,1,CV_32FC1);    
CvMat* matC = cvCreateMat(3,1,CV_32FC1);
 
void Init(void){
    IplImage ip1;
    CvScalar s;
    int i;
 
    src = Mat(480, 480, CV_8UC1, Scalar(0,0,0));
    ip1 = src;
    width = ip1.width;
    height = ip1.height;
 
    for(i=0; i<pointNUmber; i++){
        point[i].x = pointAddr[i][0];
        point[i].y = pointAddr[i][1];
        s.val[0] = 255; 
        circle(src, point[i], 3, cvScalar(255,255,255), -1);
    }
    imshow("src", src);
}
 
void work(void){
    int i;
 
    cvSetData(matA, A, CV_AUTOSTEP);
    cvSetData(matB, B, CV_AUTOSTEP);
    cvSolve(matA, matB, matC, CV_LU);
 
    for(i=0;i<3;i++){  
        printf("%f\t", matC->data.fl[i]);  
    }  
}
 
void show(void){
    int i, j;
    int result;
    CvScalar s;
    for(i=0; i<width; i++){
        result = (int)(i*i*matC->data.fl[0]) + i*matC->data.fl[1] + matC->data.fl[2];
        s.val[0] = 255;
        if(result < height){
            circle(src, cvPoint(i, result), 3, cvScalar(255,255,255), -1);
        }
    }
    imshow("dst", src);
}
 
int main(int argc, char* argv[]){
    int k;
 
    Init();
    work();
    show();
 
    waitKey(0);
    return 0;
}

代码讲解

　　1、初始化一副480X480的空白图片，接着以预先设置的三个点：{70, 420}, {160, 90}, {390, 410}为圆心，在该图片上显示出这些点。

void Init(void){
    IplImage ip1;
    CvScalar s;
    int i;
 
    src = Mat(480, 480, CV_8UC1, Scalar(0,0,0));
    ip1 = src;
    width = ip1.width;
    height = ip1.height;
 
    for(i=0; i<pointNUmber; i++){
        point[i].x = pointAddr[i][0];
        point[i].y = pointAddr[i][1];
        s.val[0] = 255; 
        circle(src, point[i], 3, cvScalar(255,255,255), -1);
    }
    imshow("src", src);
}

　　2、根据公司a*x1*x1 + b*x1 + c = y1，a*x2*x2 + b*x2 + c = y2，a*x3*x3 + b*x3 + c = y3。其中x1、x2、x3为那三个点的X坐标；
y1、y2、y3为那三个点的Y坐标；a、b、c为被拟合的抛物线参数。
　　填充矩阵：A[3][3] = [[x1*x1, x1, 1], [x2*x2, x2, 1], [x3*x3, x3, 1]]
　　          B[3]    = [y1, y2, y3];
　　将矩阵A、B作为输入参数，生成抛物线参数a、b、c,保存到matC中。

void work(void){
    int i;
 
    cvSetData(matA, A, CV_AUTOSTEP);
    cvSetData(matB, B, CV_AUTOSTEP);
    cvSolve(matA, matB, matC, CV_LU);
 
    for(i=0;i<3;i++){  
        printf("%f\t", matC->data.fl[i]);  
    }  
}

　　3、根据计算得到的抛物线参数，拟合出抛物线，并在之前的空白图片上显示出来：

void show(void){
    int i, j;
    int result;
    CvScalar s;
    for(i=0; i<width; i++){
        result = (int)(i*i*matC->data.fl[0]) + i*matC->data.fl[1] + matC->data.fl[2];
        s.val[0] = 255;
        if(result < height){
            circle(src, cvPoint(i, result), 3, cvScalar(255,255,255), -1);
        }
    }
    imshow("dst", src);
}

结果显示

　对应的效果演示如下:
     

参考资料

  http://blog.csdn.net/woxincd/article/details/7278019