Methods, systems, and apparatus, including computer programs encoded on computer storage media, for upscaling an image. One of the methods includes upscaling a low resolution image, creating first pixel subsets of the first upscaled image, creating second pixel subsets of a high resolution image, determining, for each subset in the pixel subsets, a value of a property of the pixel subset, determining, for each subset in the pixel subsets, a group of subsets to which the corresponding pixel subset belongs using the value of the property, and determining, for each of the groups of subsets, a filter to apply to each of the first pixel subsets that correspond to the pixel subsets in the group to create a final pixel subset that approximates the corresponding second pixel subset using the first pixel subset, a combination of all of the final pixel subsets representing a second upscaled image.