libvlfeat: Glossary

Column-major. A M x N matrix A is stacked with column-major order as the sequence $(A_{11}, A_{21}, \dots, A_{12}, \dots)$ . More in general, when stacking a multi dimensional array this indicates that the first index is the one varying most quickly, with the other followed in the natural order.
Opaque structure. A structure is opaque if the user is not supposed to access its member directly, but through appropriate interface functions. Opaque structures are commonly used to define objects.
Row-major. A M x N matrix A is stacked with row-major order as the sequence $(A_{11}, A_{12}, \dots, A_{21}, \dots)$ . More in general, when stacking a multi dimensional array this indicates that the last index is the one varying most quickly, with the other followed in reverse order.
Feature frame. A feature frame is the geometrical description of a visual features. For instance, the frame of a SIFT feature is oriented disk and the frame of MSER feature is either a compact and connected set or a disk.
Feature descriptor. A feature descriptor is a quantity (usually a vector) which describes compactly the appearance of an image region (usually corresponding to a feature frame).