OpenCV  4.10.0
Open Source Computer Vision
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Quasi dense Stereo

Goal

In this tutorial you will learn how to

  • Configure a QuasiDenseStero object
  • Compute dense Stereo correspondences.
#include <opencv2/core.hpp>
#include <fstream>
using namespace cv;
using namespace std;
int main()
{
cv::Mat rightImg, leftImg;
leftImg = imread("./imgLeft.png", IMREAD_COLOR);
rightImg = imread("./imgRight.png", IMREAD_COLOR);
cv::Size frameSize = leftImg.size();
Ptr<stereo::QuasiDenseStereo> stereo = stereo::QuasiDenseStereo::create(frameSize);
stereo->process(leftImg, rightImg);
cv::Mat disp;
disp = stereo->getDisparity();
cv::namedWindow("disparity map");
cv::imshow("disparity map", disp);
cv::namedWindow("right channel");
cv::namedWindow("left channel");
cv::imshow("left channel", leftImg);
cv::imshow("right channel", rightImg);
vector<stereo::MatchQuasiDense> matches;
stereo->getDenseMatches(matches);
std::ofstream dense("./dense.txt", std::ios::out);
for (uint i=0; i< matches.size(); i++)
{
dense << matches[i].p0 << matches[i].p1 << endl;
}
dense.close();
return 0;
}
n-dimensional dense array class
Definition mat.hpp:812
MatSize size
Definition mat.hpp:2160
Template class for specifying the size of an image or rectangle.
Definition types.hpp:335
std::shared_ptr< _Tp > Ptr
Definition cvstd_wrapper.hpp:23
uint32_t uint
Definition interface.h:42
void imshow(const String &winname, InputArray mat)
Displays an image in the specified window.
int waitKey(int delay=0)
Waits for a pressed key.
void namedWindow(const String &winname, int flags=WINDOW_AUTOSIZE)
Creates a window.
int main(int argc, char *argv[])
Definition highgui_qt.cpp:3
"black box" representation of the file storage associated with a file on disk.
Definition core.hpp:102
STL namespace.

Explanation:

The program loads a stereo image pair.

After importing the images.

cv::Mat rightImg, leftImg;
leftImg = imread("./imgLeft.png", IMREAD_COLOR);
rightImg = imread("./imgRight.png", IMREAD_COLOR);

We need to know the frame size of a single image, in order to create an instance of a QuasiDesnseStereo object.

cv::Size frameSize = leftImg.size();
Ptr<stereo::QuasiDenseStereo> stereo = stereo::QuasiDenseStereo::create(frameSize);

Because we didn't specify the second argument in the constructor, the QuasiDesnseStereo object will load default parameters.

We can then pass the imported stereo images in the process method like this

stereo->process(leftImg, rightImg);

The process method contains most of the functionality of the class and does two main things.

  • Computes a sparse stereo based in "Good Features to Track" and "pyramidal Lucas-Kanade" flow algorithm
  • Based on those sparse stereo points, densifies the stereo correspondences using Quasi Dense Stereo method.

After the execution of process() we can display the disparity Image of the stereo.

cv::Mat disp;
disp = stereo->getDisparity();
cv::namedWindow("disparity map");
cv::imshow("disparity map", disp);

At this point we can also extract all the corresponding points using getDenseMatches() method and export them in a file.

vector<stereo::MatchQuasiDense> matches;
stereo->getDenseMatches(matches);
std::ofstream dense("./dense.txt", std::ios::out);
for (uint i=0; i< matches.size(); i++)
{
dense << matches[i].p0 << matches[i].p1 << endl;
}
dense.close();