【计算机视觉基础】IPM

IPM

逆透视变换的整体过程：

 

 灭点的求解

假设Zc为1，

 

 消失点可以认为是空间直线上无穷远处的点投影在图像上所成的像点。对于空间中某一直线L，方向为（dx,dy,dz），给定直线上坐标（ax,ay,az）,所以直线上任一点A可以表示为:

 

 

 

 当趋于无穷时可以得到

 

 

从而得到消失点的坐标。

 注：逆透视变换的范围不能到达消失点，否则不能还原。

code

#if 0
void xyp2ipmp(cv::Mat& xyp, cv::Mat& ipmp, cv::Mat& xylim, Size& sz){

    //xylimist_[0]-latteral/xylimist_[1]-longitudinal...
    //ipmp-row0-cols-latteral/ipmp-row1-rows-longitudinal...

    double xmin = 0, xmax = 0, ymin = 0, ymax = 0;
    minMaxLoc(xylim.row(0), &xmin, &xmax);
    minMaxLoc(xylim.row(1), &ymin, &ymax);

    double stepcol = (xmax - xmin) / sz.width;
    double steprow = (ymax - ymin) / sz.height;

    cv::Mat tempx = cv::Mat::ones(1, xyp.cols, CV_64FC1) * xmin;
    cv::Mat tempy = cv::Mat::ones(1, xyp.cols, CV_64FC1) * ymax;

    ipmp = cv::Mat::zeros(2, xyp.cols, CV_64FC1);
    ipmp.rowRange(0, 1) = ( xyp.rowRange(0, 1) - tempx ) / stepcol;
    ipmp.rowRange(1, 2) = ( tempy - xyp.rowRange(1, 2) ) / steprow;
    for (int i = 0; i < xyp.cols; i++ )
    {
        double y = ipmp.at<double>(1, i);
        if( y > ymax){
            ipmp.at<double>(1, i) = ymax;
        }
    }
    
}
#endif

 

code

#if 0
    //IPM-parameters...    
    double left_upper_x = 1;//left
    double left_upper_y = 330;//top-greater than 320...
    double right_down_x = 1280;//right...
    double right_down_y = 720;//bottom...
    double uvlimist[8] = { left_upper_x, right_down_x, left_upper_x, right_down_x, 
                           left_upper_y, left_upper_y, right_down_y, right_down_y };
    cv::Mat uvlmt = cv::Mat(2, 4, CV_64FC1, uvlimist);

     //I2G
    cv::Mat xylimit;
    imagetoground(uvlmt, xylimit, h, roll, pitch, camera_param_KK);
     //G2I
    cv::Mat uvgd;
    cv::Size sz = cv::Size(PROB_W, PROB_H);//Size(srcimage.cols, srcimage.rows)
    groundtoimage(xylimit, uvgd, sz, h, roll, pitch, camera_param_KK );
#endif

 

code

#if 1
        //IPM...
        cv::Mat outimage, coord;
        src2ipm( prob, uvgd, outimage, coord, sz, h, roll, pitch, camera_param_KK );
        outimage.convertTo(outimage, CV_8UC1);
        cv::Mat ipm3 = cv::Mat::zeros(PROB_H, PROB_W, CV_8UC3);
        cv::cvtColor(outimage, ipm3, COLOR_GRAY2BGR);

        //
        //cv::Mat uvp = cv::Mat::zeros(2, probp.size(), CV_8UC1);
        cv::Mat uvp = cv::Mat::zeros(2, probp.size(), CV_64FC1);//data-type...
        for (unsigned int i = 0; i <probp.size(); i++ )
        {
            uvp.at<double>(0, i) = probp[i].x;//cols-width.
            uvp.at<double>(1, i) = probp[i].y;//rows-height.
            //std::cout <<  uvp.at<double>(0, i) << "-----" << probp[i].x <<std::endl;
            //std::cout <<  uvp.at<double>(1, i) << "-----" << probp[i].y <<std::endl;
        }
        cv::Mat ipmps, xyp;
        //std::cout << "uvp:" << uvp << std::endl;
        imagetoground(uvp, xyp, h, roll, pitch, camera_param_KK);
        xyp2ipmp(xyp, ipmps, xylimit, sz);
        ipmps.convertTo(ipmps, CV_32SC1);
        for (unsigned int i = 0; i <probp.size(); i++ )
        {
            cv::Point ipmp;
            ipmp.x = ipmps.at<int>(0, i);
            ipmp.y = ipmps.at<int>(1, i);
            if (plabel[i] == 1)//-barrier
            {
                cv::circle(ipm3, ipmp, 3, cv::Scalar(240, 32, 160), -1); //
                //cv::putText(orig, std::to_string(i), pt, CV_FONT_NORMAL, 0.1, cv::Scalar(255, 255, 255));
            }
            else if (plabel[i] == 0)//-undifined
            {
                cv::circle(ipm3, ipmp, 3, cv::Scalar(255, 255, 0), -1); //
                //cv::putText(orig, std::to_string(i), pt, CV_FONT_NORMAL, 0.1, cv::Scalar(255, 255, 255));
            }
    
        }

        cv::imshow("ipmp", ipm3);
        cv::waitKey(1);//unit-ms.
        sprintf(output_path,"./ipmp/00000%05d.png",cnt);
        cv::imwrite(output_path, ipm3);
#endif

 

 

参考

1. matlab_逆透视变换详解 及 代码实现(一);

2. matlab_逆透视变换详解 及 代码实现(二);

3. matlab_github;

完