New algorithms for preserving edges in low-bit-rate wavelet-based image compression

With the growing importance of low-bandwidth applications such as wireless access to the Internet, images are often sent or received at low bit rates. At these bit rates, images suffer from significant distortion and artifacts, making it difficult for those viewing the images to understand them. In this paper, we present two progressive compression algorithms that focus on preserving the clarity of important image features, such as edges, at compression ratios of 100:1 and higher. The first algorithm transmits a standard SPIHT bit stream and then detects the location of edges in the compressed image. The decoder applies a linear edge-enhancement procedure to improve the clarity of the encoded edges. The second algorithm extracts the locations of straight-line edges in the image at the encoder, and the decoder applies edge extraction, combination, and a linear edge-enhancement procedure to improve the clarity of the edges. With both algorithms, features in the images that may be important for recognition are well preserved, even at very low bit rates. (c) 2012 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.