Reavy M D, Boncelet C G
Dept. of Electr. and Comput. Eng., Delaware Univ., Newark, DE 19716, USA.
IEEE Trans Image Process. 2001;10(5):669-76. doi: 10.1109/83.918560.
This paper presents the block arithmetic coding for image compression (BACIC) algorithm: a new method for lossless bilevel image compression which can replace JBIG, the current standard for bilevel image compression. BACIC uses the block arithmetic coder (BAC): a simple, efficient, easy-to-implement, variable-to-fixed arithmetic coder, to encode images. BACIC models its probability estimates adaptively based on a 12-bit context of previous pixel values; the 12-bit context serves as an index into a probability table whose entries are used to compute p(1) (the probability of a bit equaling one), the probability measure BAC needs to compute a codeword. In contrast, the Joint Bilevel Image Experts Group (JBIG) uses a patented arithmetic coder, the IBM QM-coder, to compress image data and a predetermined probability table to estimate its probability measures. JBIG, though, has not get been commercially implemented; instead, JBIG's predecessor, the Group 3 fax (G3), continues to be used. BACIC achieves compression ratios comparable to JBIG's and is introduced as an alternative to the JBIG and G3 algorithms. BACIC's overall compression ratio is 19.0 for the eight CCITT test images (compared to JBIG's 19.6 and G3's 7.7), is 16.0 for 20 additional business-type documents (compared to JBIG's 16.0 and G3's 6.74), and is 3.07 for halftone images (compared to JBIG's 2.75 and G3's 0.50).
本文介绍了用于图像压缩的块算术编码（BACIC）算法：一种用于无损二值图像压缩的新方法，它可以替代当前二值图像压缩标准JBIG。BACIC使用块算术编码器（BAC）：一种简单、高效、易于实现的可变到固定算术编码器来对图像进行编码。BACIC基于先前像素值的12位上下文自适应地对其概率估计进行建模；该12位上下文用作概率表的索引，概率表的条目用于计算p(1)（位等于1的概率），这是BAC计算码字所需的概率度量。相比之下，联合二值图像专家组（JBIG）使用专利算术编码器IBM QM编码器来压缩图像数据，并使用预定概率表来估计其概率度量。然而，JBIG尚未商业化实现；相反，JBIG的前身，即3类传真（G3）仍在使用。BACIC实现了与JBIG相当的压缩率，并作为JBIG和G3算法的替代方案被引入。对于八个CCITT测试图像，BACIC的总体压缩率为19.0（相比之下，JBIG为19.6，G3为7.7）；对于另外20个商业类型文档，压缩率为16.0（相比之下，JBIG为16.0，G3为6.74）；对于半色调图像，压缩率为3.07（相比之下，JBIG为2.75，G3为0.50）。
