1. A method for indexing in an image decoder, comprising: identifying a tile in an image, wherein said image comprises a plurality of tiles, wherein each tile includes color data associated with a plurality of pixels; asymmetrically providing a plurality of indices throughout said tile; identifying a pixel in said tile; determining a corresponding rectangular grid including said pixel, wherein said corresponding rectangular grid comprises a group of four indices; and determining an index for said pixel by bilinearly filtering said group of indices in relation to said pixel.