O2TC：利用二進制優點的高品質、低複雜度二進制材質壓縮法

Abstract

對於儲存空間或是傳輸頻寬有限的裝置材質壓縮是必要的。雖然有損耗的壓縮是有效的，但是解壓縮後的材質品質是一個問題。我們提出一個可以達成壓縮率高、解碼簡單而且解碼後的品質高的二進制材質壓縮法—O2TC (Order of 2 Texture Compression)。O2TC試著利用二進制系統的優點。他的特點包含:對用來表示的基本顏色做明智的選擇與編碼、簡單而且可平行接收方塊材元。我們使用一對基本顏色或是一個基本色與一個差值，與簡單快速的二進制內插與外插計算出用來表示的顏色不需要使用乘法或是除法。因截斷所造成的最大可能誤差也盡量被使用隱藏位元給最小化。我們進一步減少使用2的補數算術的壓縮/解壓縮誤差。並且透明分量也可以使用一樣的方法。跟著名的S3TC的DXT5方法比較，我們有更簡單的解壓縮方式與更好的解壓縮後影像品質，在有透明分量的材質上，O2TC RGB888, 8-color, 與Plain64-64 options 方法分別領先了0.37, 2.80 and 0.15 dB。

Texture compression is necessary for limited storage and low bandwidth devices. While lossy compressions are effective, quality of texture after recovery becomes an issue. We propose an order-of-two texture compression method—O2TC (Order of 2 Texture Compression) to achieve high compression rate, easy decompression, and high quality after decompression. O2TC tries to exploit virtues in binary system. Its attributes include: judicious selection and coding of representative base colors, and simple and parallelizable retrieval of block of texels. We use either a pair of base colors or a base colors and a difference, and simple and fast binary calculations—without *, ÷ or approximation—to inter/extrapolate them into representative colors. Truncation error upper bound is also minimized with implicit color bits. With 2’s complement arithmetic, we further reduce the compression/decompression error. And alpha channel can be treated the same. Compared with renowned S3TC’s DXT5, our method has much simplified decompression with better texture quality—0.37, 2.80 and 0.15 dB better on average with O2TC RGB888, 8-color, and Plain64-64 options, respectively, on popular alpha maps.