CODEWITHSUNDEEP
c++opencv
axl
axl

Reputation: 41

Can't distort back image in opencv C++

I am trying to distort back an image in opencv. At first the image captured with a pinhole camera is undistort thanks to cv::undistort(raw, undist, cameraMatrix, distCoeffs); which is working. Now I am trying to distort back undist to it's original state with the patch that I found here: http://code.opencv.org/issues/1387 but so far I have not manage to make it work. Here is the code:

void distort(const cv::Mat& src, cv::Mat& dst, const cv::Mat& cameraMatrix, const cv::Mat& distCoeffs)
{

  cv::Mat pixel_locations_src = cv::Mat(src.size(), CV_32FC2);

  for (int i = 0; i < src.size().height; i++) {
    for (int j = 0; j < src.size().width; j++) {
      pixel_locations_src.at<cv::Point2f>(i,j) = cv::Point2f(j,i);
    }
  }

  cv::Mat fractional_locations_dst = cv::Mat(src.size(), CV_32FC2);

  cv::Mat pixel_locations_dst = cv::Mat(src.size(), CV_32FC2);

  cv::undistortPoints(pixel_locations_src, pixel_locations_dst, cameraMatrix, distCoeffs);

  const float fx = cameraMatrix.at<double>(0,0);
  const float fy = cameraMatrix.at<double>(1,1);
  const float cx = cameraMatrix.at<double>(0,2);
  const float cy = cameraMatrix.at<double>(1,2);

  // is there a faster way to do this?
  for (int i = 0; i < fractional_locations_dst.size().height; i++) {
    for (int j = 0; j < fractional_locations_dst.size().width; j++) {
      const float x = fractional_locations_dst.at<cv::Point2f>(i,j).x*fx + cx;
      const float y = fractional_locations_dst.at<cv::Point2f>(i,j).y*fy + cy;
      pixel_locations_dst.at<cv::Point2f>(i,j) = cv::Point2f(x,y);
    }
  }

  cv::remap(src, dst, pixel_locations_dst, cv::Mat(), CV_INTER_LINEAR);
}

I tried to pass a RGB image to the function but since undistortPoints takes a 1*N, 2 channels matrix the code will fire an assertion at undistortPoints I don't understand why distort() takes a 1xN matrix as input.

Any light on the topic would be great. Thanks

Upvotes: 3

Views: 1235

Answers (1)

axl
axl

Reputation: 41

I finally used a different approach, I only needed to distort back a certain set of points, here is the code:

void DistortPoints(const std::vector<cv::Point2f> & src, std::vector<cv::Point2f> & dst, const cv::Mat& cameraMatrix, const cv::Mat& distorsionMatrix)
{
    double fx = cameraMatrix.at<double>(0,0);
    double fy = cameraMatrix.at<double>(1,1);
    double cx = cameraMatrix.at<double>(0,2);
    double cy = cameraMatrix.at<double>(1,2);
    std::vector<cv::Point3f> src2;

    for (int i = 0; i < src.size(); i++)
        src2.push_back(cv::Point3f((src[i].x - cx) / fx, (src[i].y - cy) / fy, 0));

    cv::Mat rVec(3, 1, cv::DataType<double>::type, cv::Scalar(0)); // Rotation vector
    cv::Mat tVec(3, 1, cv::DataType<double>::type, cv::Scalar(0)); // Translation vector

    std::vector<cv::Point2f> dst2;
    cv::projectPoints(src2, rVec, tVec, cameraMatrix, distorsionMatrix, dst);
}

Upvotes: 1

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