The present invention provides a scheme for compressing the color components
of image data. The pixel data is grouped into a plurality of tiles for storage.
A test is performed to determine if a tile can be compressed so that its size after
compression is less than its size before compression. If so, the tile is compressed.
A tile table is provided that includes a flag that can be set for each tile that
is compressed. In a data transfer from memory to a graphics processor, the tile
table is examined to identify those tiles that are compressed and must be decompressed
prior to use. In one embodiment, a number of compression schemes are available
for use on a tile and the best compression scheme is chosen on a tile by tile basis.
The invention includes an identifying code for each compression scheme (stored
as a value in each compressed tile).