An analytical study of subpixel-based image down-sampling patterns in frequency domain

Subpixel-based image down-sampling is a class of methods that can provide improved apparent resolution of the down-scaled image compared to the pixel-based methods. The frequency characteristics of all possible subpixel-based down-sampling patterns for RGB vertical stripes are analytically studied in this paper. Our proposed algorithm reveals that there are merely seven equivalent energy distributions in the luminance frequency spectrum. To achieve higher luminance resolution, we then calculate and choose the optimal down-sampling pattern with anti-aliasing low-pass filter designed for it so as to maximize the energy of the luminance component within the cut-off shape. Experimental results show that the proposed method provides sharper images compared to the state-of-art subpixel-based methods, with little color distortion.