Shape from positional-contrast

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Graphical queries for searching pictorial information are increasingly important in fields like design, architecture, and engineering, where images convey essential information. Sketching these queries helps express the visual characteristics of desired objects. However, a challenge arises in identifying necessary shape properties within sketches, as they are often imprecise and influenced by the artist's limitations. The concept of pictorial space is crucial in addressing this issue. New approaches are needed to manage imprecise shape information in two dimensions. A proposed relation algebra of intersection-free relations facilitates reasoning about qualitative line arrangements in the plane. This theory extends to characterizing polygons by deriving qualitative properties that assist in their description. It emphasizes that only line arrangements that are easily sketched and perceived are considered distinct. The introduction of positional-contrast highlights that the specific arrangements of line segments, and their relative positions, serve as a powerful means to define necessary shape properties. This methodology is particularly effective for utilizing graphical queries in the search for historical objects.