2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/33280This paper presents an invariant under scaling and linear brightness change. The invariant is based on differentials and therefore is a local feature. Rotationally invariant 2-d differential Gaussian operators up to third order are proposed for the implementation of the invariant. The performance is analyzed by simulating a camera zoom-out.5 pages, 7 figuresComputer Vision and Pattern RecognitionI.4.7text