In a method for generating a depth map for an image, an image processing apparatus is configured to: determine a depth level for each of at least two objects in the image according to an angle of incidence in which light incident upon the object is projected onto an image sensor of a light-field camera; calculate a depth value of the depth level associated with one of the objects; estimate a depth value for the depth level associated with another one of the objects; and generate a depth map according to the depth values. The depth value is estimated based on a distance between first and second locations on the image sensor, on which light incident upon the reference and relative objects are projected.