Compression of Multispectral Images - Combining Spatial and Spectral Compression

One major disadvantage of multispectral imaging is the amount of data that needs to be stored for each multispectral image. In the past, several authors have proposed compression schemes to overcome this disadvantage. Most of these papers dealt with compression either in the spectral or in the spatial realm only, although some authors proposed to divide the data into luminance and color components and to subsample the latter, resulting in a combined method. Unfortunately, using multispectral imaging the luminance component depends on the illuminant used during the reconstruction of the color. Using a narrowband illuminant every single wavelength could correspond to the luminance information. This paper proposes a method that overcomes this difficulty by using a more basic approach. The reason, why it is possible to subsample the color channels in conventional color imaging is the dependence of the MTF of the human eye on the wavelength of the observed light. Therefore, it is possible to subsample each spectral band separately (yielding spatial compression). Furthermore, a spectral compression method is proposed, that is compatible to the spatial compression, resulting in a method that combines spatial and spectral compression of the multispectral image. Finally, the compatibility to conventional imaging will be addressed and it will be shown, that the new method allows achieving limited compatibility.