get rectified image and put disparity image

Stereo_match.cpp

// for image processing
#include "opencv2/calib3d/calib3d.hpp"
#include "opencv2/imgproc.hpp"
#include "opencv2/imgcodecs.hpp"
#include "opencv2/highgui.hpp"
#include "opencv2/core/utility.hpp"
#include "opencv2/ximgproc/disparity_filter.hpp"
#include <stdio.h>
#include <stdlib.h>

cv::Rect computeROI(cv::Size2i src_sz, cv::Ptr<cv::StereoMatcher> matcher_instance)
{
    using namespace cv;
    using namespace cv::ximgproc;

    int min_disparity = matcher_instance->getMinDisparity();
    int num_disparities = matcher_instance->getNumDisparities();
    int block_size = matcher_instance->getBlockSize();

    int bs2 = block_size/2;
    int minD = min_disparity, maxD = min_disparity + num_disparities - 1;

    int xmin = maxD + bs2;
    int xmax = src_sz.width + minD - bs2;
    int ymin = bs2;
    int ymax = src_sz.height - bs2;

    Rect r(xmin, ymin, xmax - xmin, ymax - ymin);
    return r;
}

void show_stereo(const cv::Mat imgLeft,const cv::Mat imgRight){
    using namespace cv;
    using namespace cv::ximgproc;
    
    Mat imgDisparity16S = Mat( imgLeft.rows, imgLeft.cols, CV_16S );
    Mat imgDisparity8U = Mat( imgLeft.rows, imgLeft.cols, CV_8UC1 );
    Mat filtered_disp;
     //-- 2. Call the constructor for StereoBM
    int ndisparities = 16*5;   /**< Range of disparity */
    int SADWindowSize = 21; /**< Size of the block window. Must be odd */

    Ptr<StereoBM> sbm = StereoBM::create( ndisparities, SADWindowSize );
    sbm->setTextureThreshold(0);
    sbm->setUniquenessRatio(0);
    Rect ROI = computeROI(imgLeft.size(),sbm);
    // define filter
    Ptr<DisparityWLSFilter> wls_filter;
    wls_filter = createDisparityWLSFilterGeneric(false);
    wls_filter->setDepthDiscontinuityRadius((int)ceil(0.33*SADWindowSize));

    //-- 3. Calculate the disparity image
    sbm->compute( imgLeft, imgRight, imgDisparity16S );

    // Post Filtering
    double lambda,sigma;
    lambda = 8000.0;
    sigma = 1.5;
    wls_filter->setLambda(lambda);
    wls_filter->setSigmaColor(sigma);
    wls_filter->filter(imgDisparity16S,imgLeft,filtered_disp,Mat(),ROI);
    
    //-- Check its extreme values
    double minVal; double maxVal;

    minMaxLoc( filtered_disp, &minVal, &maxVal );

        
    //-- 4. Display it as a CV_8UC1 image
    filtered_disp.convertTo( imgDisparity8U, CV_8UC1, 255/(maxVal - minVal));

    namedWindow( "Disparity", WINDOW_NORMAL );
    imshow( "Disparity", imgDisparity8U );

    waitKey(1);

}