Design of an improved lossless halftone image compression codec

摘要

The popularity of high-resolution digital printers and the growing computational requirements of new applications such as printing-on-demand and personalized printing have increased the need for fast and efficient lossless halftone image compression. In a previous paper, we have shown that the compression performance can be improved significantly by adapting the context template to the halftone parameters. Unfortunately, this variability in data dependency makes the modeling stage more complex and slows down the overall compression scheme. In this paper, we describe the design of an improved block-based software and hardware implementation. The software implementation uses complementary line-shifting to by-pass the adaptivity of the template. The hardware implementation is based on the automated construction of a microcoded program from a given template. Experimental results show that our improved implementation achieves approximately the same processing speed as when the fixed context template is applied. The proposed implementation is also of importance for the emerging JBIG2 standard which uses up to four adaptive template pixels.