1. A method of generating a compressed image of an original image that includes a plurality of pixels, each pixel having a first color value, a second color value, and a third color value, the method comprising: storing an unweighted sum of the first color value and the second color value for each pixel in the plurality of pixels as a first channel; subsampling, among the plurality of pixels, a difference between the first color value and the second color value as a second channel; subsampling, among the plurality of pixels, the third color value as a third channel; and storing the first channel, the second channel, and the third channel as the compressed image.