Image reading

Image low pass filtering

Emphasis on low image intensities:

Background subtraction, horizontal stripes removal

Obtaining one-dimensional (special case) Fourier spectra for image fragments using https://github.com/leerichardson/tree-swdft-2D

Finding the separation line points where spectra main frequencies abruptly change

Preliminary filtering of points using cv::partition and nanoflann library

Using RANSAC to find the separation line using separation line points

Using CERES solver to refine the separation line

Using both adaptiveThreshold and binary background subtraction to generate threshold image

Using thinning to obtain lines skeletons

Calling erode/dilate to filter out vertical lines

Invoking HoughLinesP to generate lines from skeletons

Merging lines according to https://stackoverflow.com/a/51121483/10472202

Filtering out short lines

Cutting lines using the RANSAC/CERES separation line mentioned above

Filtering out short lines once more

Search for the beginnings of short stripes with "known good" SURF data

Movement to the left and up along long lines

Merging HoughLinesP and SURF results to obtain the final data