1. A method for restoring compressed image data, comprising: using a computer to perform the following steps: converting a color cell having a first low bit per pixel color value and a second low bit per pixel color value to a first high bit per pixel color value and a second high bit per pixel color value, wherein the color cell is compressed; interpolating between the first high bit per pixel color value and the second high bit per pixel color value to produce a third high bit per pixel color value and a fourth high bit per pixel color value; and reconstructing the color cell from luminance-encoded bitmasks, the first high bit per pixel color value, the second high bit per pixel color value, the third high bit per pixel color value and the fourth high bit per pixel color value.