From this article
The High-Resolution Imaging Science Experiment (HiRISE) camera on NASA's Mars Reconnaissance Orbiter plays an important role in evaluating candidate landing sites on Mars. HiRISE took about 150 images of candidate InSight landing sites, covering nearly all of the ground of the final site.
I came to know that the site selection 150 images were taken to land InSight Mars lander. But to process those images, what kind of processing was done to identify the flat ground, rocks, craters, etc.?