1. A method for rendering an image from a light-field camera, the light-field camera generating a raw light-field image in response to detecting light rays incident on a focal plane using a photosensor which detects the light rays from a scene, the light rays being incident on an array of microlenses and passed to different locations on the focal plane, the raw light-field image being composed of a plurality of micro-images, the method to be implemented by an image rendering system and comprising: (A) generating, by the image rendering system, feature data, which includes feature elements associated with corresponding position information, associated with the raw light-field image, and obtained based on the raw light-field image and a preset threshold condition; (B) generating, by the image rendering system, a raw focused image from the raw light-field image; (C) obtaining, by the image rendering system, a virtual focus position that is designated on the raw focused image; and (D) refocusing, by the image rendering system, the raw focused image according to the virtual focus position by updating pixel values of pixels of the raw focused image that correspond respectively in position to the feature elements of the feature data, so as to generate a refocused image; wherein a first portion of pixels of the refocused image that correspond respectively in position to the feature elements of the feature data has pixel values which are determined by performing a refocusing operation upon the raw light-field image according to the virtual focus position; and wherein a second portion of the pixels of the refocused image that do not correspond in position to the feature elements of the feature data has pixel values which are determined according to pixel values of pixels of the raw focused image that correspond respectively in position to the second portion of the pixels of the refocused image.