1. An image-processing method comprising the steps of: (i) providing a stack for storing a predetermined number of frame portions; (ii) obtaining an image including a target object, the image being formed by an array of pixels; (iii) extracting a frame portion from the image, the frame portion being at least a portion of the pixels forming the image, corresponding to a region of interest in the image, the region of interest comprising the target object; the frame portion having an associated phase, representative of the sub-pixel translation shift of the region of interest defined by the frame portion, (iv) storing the frame portion in the stack, the storing including discarding an oldest previously stored frame portion from the stack if the number of frame portions stored in the stack has reached the predetermined number; (v) repeating steps (ii) to (iv) a plurality of times; and (vi) calculating a super-resolved image from the plurality of stored frame portions, including a sub-step of averaging all frame portions in the stack having a phase substantially equal to a given phase.