Method for upscaling an image and apparatus for upscaling an image

Known super-resolution algorithms are inefficient due to a high degree of redundant calculations, require search operations such as block matching for finding nearest neighbors, and achieve only small magnification factors. An improved method for upscaling an image comprises steps of upscaling the image by pixel interpolation to obtain a coarse upscaled image, and, for each pixel of the coarse upscaled image, determining a nonlinear regression function for a patch of pixels around a current pixel of the coarse upscaled image and enhancing the value of the current pixel by adding the result of the nonlinear regression function, wherein a pixel of an upscaled image is obtained. The nonlinear regression function is obtained from a trained regression tree, based on geometric features of the patch.