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Abstract:In this paper, we consider a model of lossless image compression in which each band of a multispectral image is coded using a prediction function involving values from a previously coded band of the compression, and examine how the ordering of the bands affects the achievable compression.We present an efficient algorithm for computing the optimal band ordering for a multispectral image. This algorithm has time complexity O(n 2 ) for an n-band image, while the naive algorithm takes time (n!). A slight variant of the optimal ordering problem that is motivated by some practical concerns is shown to be NP-hard, and hence, computationally infeasible, in all cases except for the most trivial possibility.In addition, we report on our experimental findings using the algorithms designed in this paper applied to real multispectral satellite data. The results show that the techniques described here hold great promise for application to real-world compression needs.Index Terms-Compression, lossless compression, image compression, multispectral images, satellite data, NPcompleteness.
Article:1 INTRODUCTION MULTISPECTRAL satellite images require enormous amounts of space, and with NASA's project EOS (the Earth Observing System), data will be generated at an unprecedented rate. The estimates are that over a terabyte (10 12 bytes) of data will be generated every day by the EOS satellites, most of it multispectral image data. Largely due to this fact, a lot of attention has recently been focused on compression of multispectral images [5]. However, most of the compression methods that exploit spectral as well as spatial redundancy have been lossy compression algorithms, and for archival storage and for certain applications it is important to use lossless compression in order to preserve all of the data that is collected. One notable exception to this is the work of Roger and Cavenor [4] who extensively study various prediction and coding methods used for lossless compression of AVIRIS data. Table 1 lists some current, widely used multispectral sources, with their acronyms, full names, and basic properties-it is data from these sensors that we used in this study.In this paper, we study lossless compression of multispectral images. Spectral redundancy is extracted by coding each band of the multispectral image by making use of a second -prediction band.‖ In much the same way that standard single-image lossless compression is separated into the two separate components of prediction and coding, we divide the lossless compression of multispectral images into three components: band ordering, prediction, and coding. The new stage, band ordering, refers to selecting a permutation...