Alpha Compression with Variable Data Formats

Abstract

Based on the insight into the essential differences between transparency and color, we present a novel alpha compression scheme, called EAC (Enhanced Alpha Compression), as an improvement to that of DXT5. EAC defines new compression data formats, and employs clustering algorithms combined with linear interpolation method used in DXT5 to compress 16 input alpha values to 64 bits. The compressed block has three possible formats, corresponding to two process modes in decompression. Results show that EAC improves the average PSNR with about 0.2 dB compared to alpha compression of DXT5 over a set of test images. Moreover, the average cell area of hardware implementation is reduced by about 25 percent, and the power consumption is lowered by 21.66 percent 26.75 percent.