Several intersecting lines (top left), the |ψ₂| Minkowski map at a window size large enough for an increased line density (top right), the resulting line density (bottom left), and the |ψ₂| Minkowski map at triple window size (bottom right, same scale as the other Minkowski map). In spite of setting a low line density threshold, no part of the image is detected as a bubble because the decreasing |ψ₂ | condition is not fulfilled.