Extracting biometric information from an eye generally includes a procedure for the segmentation of the iris within an eye image. In addition to this segmentation of the iris, the portion of the iris that is occluded by the eyelids (upper or lower) can be estimated. This estimation is performed because, during normal human activity, the entire iris of a person is rarely visible. Estimating the portion of the iris occluded by the eyelids has presented challenges. Embodiments of eyelid shape estimation described herein advantageously can be used for estimating the portion of the iris occluded by eyelids. Systems and methods for eyelid shape estimation are disclosed. In one aspect, after receiving an eye image of an eye (e.g., from an image capture device), an eye-box is generated over an iris of the eye in the eye image. A plurality of radial lines can be generated from approximately the center of the eye-box to an upper edge or a lower edge of the eye box. Candidate points can be determined to have local maximum derivatives along the plurality of radial lines. From the candidate points, an eyelid shape curve (e.g., for an upper eyelid or a lower eyelid) can be determined by fitting a curve (e.g., a parabola or a polynomial) to the candidate points or a subset of the candidate points.
