Make visualization of the feature slopes.
calibration/cg_visualize_fslopes dataset_parameters.json slopes.json out_visualization.png [width=200] [exaggeration=1] [dataset_group]
Like calibration/cg_slopes_viewer, but saves the visualization in a PNG file instead of showing GUI. Length (width) of shown line segments for the horizontal and vertical slopes on each feature point, and exxageration factor of slopes can be set. Background is the view on which these feature slopes are taken.