Scheme of an image pixel structure before and after the conversion from a hexagonal grid to a square grid. Each point represents a pixel center (the standard image pixels are reported in blue, and the ones added with the sharpening process are reported in red), while each number is an impact point position. In the top panel, the position of the IPs on the square grid without corrections is reported, while in the bottom panel the position of the IPs on the square grid takes a fine-tuning correction into account.