Products Demos Download Register Help

Report of the ISO
ON CARTESIAN PERCEPTUAL COMPRESSION

In July 1995, the International Organization for Standardization (ISO) Working Group on Coding for Still Pictures (ISO/IEC JTC1/SC29/WG1) tested Cartesian Perceptual Compression (CPC) in comparative tests against several other information-theoretically lossless and lossy binary image compression methods. This document summarizes the findings of these tests.

The ISO report N238, "Image Quality Test Results for JTC 1.29.10", is made available here as well, in CPC format. Interestingly, the report itself serves as an excellent example of CPC compression, requiring less than 3K bytes per page to store high-resolution images of the pages, a factor of 6.3:1 better than TIFF Group 4. The ISO distributed the report initially in rich text format (RTF), requiring some 23.7 times more space than CPC format.

The ISO results show that:

• The lossy methods (CPC; SPM, an AT&T proposal; and reduced-resolution JBIG) well outperformed the lossless methods in compression ratio, by a factor of 2:1 or more on the very difficult text-type test pages.
• Of these methods, the image quality for reduced-resolution JBIG was hopelessly inadequate.
• Of the remaining methods (CPC and SPM), CPC had better coverage (SPM was inapplicable to nontextual images), better compression ratio, was an order of magnitude faster, and required only a fixed amount of memory.
• In a comparison of overall subjective image quality, CPC outperformed all the other methods, including lossless JBIG.
• In legibility tests, a fine-grained test of textual image quality, CPC well outperformed all other lossy methods, and was essentially indistinguishable from lossless coding, even at tiny point sizes (three and four point).

© 1998-1999 Cartesian Products, Inc.	Contact Cartesian