Alpha Compression with Variable Data Formats

The alpha channel compression of texture elements is an integral part of texture compression.A novel alpha compression scheme,called Loongson alpha compression(LAC),is proposed based on an insight into the essential difference between transparency and color.LAC defines 3 alpha compression data formats,employs clustering algorithms combined with linear interpolation method used in DXT5 to compress 16 input alpha data to a 64-bit block,and decompresses the block flexibly.Both compression and decompression are implemented for LAC and DXT5's alpha channel.Experimental results show that LAC improves the average PSNR with about 0.25dB over a set of test images and reduces about 18% of alpha compression time,as compared to DXT5 alpha compression.Moreover the average cell area of the hardware implementation is lowered by about 25% and the power consumption is reduced by 10% ~ 30%.