Network-conscious GIF image transmission over the Internet

摘要

Traditional image compression techniques seek the smallest possible file size for a given level of image quality. By contrast, network-conscious image compression techniques take into account the fact that a compressed image will be transmitted over a packet-switched network that may lose and reorder packets. We describe GIFNCa, a network-conscious revision of the popular GIF89a standard. As with GIF89a, GIFNCa compresses an image using LZW encoding, however GIFNCa does so using an Application Level Framing approach. The data is segmented into path MTU-size data units, each of which can be independently decompressed and displayed on its own. Under lossy network conditions. when used in combination with an unordered transport protocol, GIFNCa permits faster progressive display at the receiver than GIF89a over an ordered transport protocol. This advantage comes in exchange for a small penalty in overall compression. This paper defines GIFNCa, and presents preliminary experimental data concerning this tradeoff. The overall goal of this research is to illustrate (1) the value of considering network characteristics in designing image formats, and (2) the value of unordered transport service.