feret

Feret is a surname of French origin and may refer to individuals who bear the name in various fields. In addition to its use as a family name, the term appears in scientific and technical contexts where it denotes a specific type of measurement.

In geometry and digital image analysis, the Feret diameter, also called the caliper diameter, is a size descriptor for two-dimensional objects. It is defined as the distance between two parallel lines tangent to the object's boundary, measured in a particular direction. The measurement is dependent on the orientation of the lines, so rotating the direction yields different Feret diameters for the same object. This concept is useful for characterizing elongated or irregular shapes where simple area or bounding box metrics are insufficient.

Common variants include the maximum Feret diameter, which is the greatest distance across the object between two parallel tangents, and the minimum Feret diameter, the smallest such distance. The angle associated with the orientation of the measuring direction is known as the Feret angle. Together, Feret diameters and Feret angles provide a set of shape descriptors that capture size and orientation.

Feret measurements are widely used in image analysis, materials science, biology, and quality control. They complement other metrics such as area, perimeter, and equivalent diameter to analyze object morphology, orientation distributions, and dimensional properties in both scientific research and industrial applications.