Satellite images are often composed of several bands taken at different spectral windows. If you have loaded one of those multi-band formats (on limit, the following is applicable to RGB images as well), you can choose to see only one band or to compose a false color image from the available bands. The figure below shows an example of a composition of bands 8-11-14 of an ENVISAT image. Note that the fact that a band shows on the Bands List figure does not imply that it loaded on memory. To save it, upon loading multi-band files only a few bands are stored in memory. As a consequence, for several band combinations it may me necessary to read them from disk, which takes a little longer.
The Compute PCA button computes the Principal Component Analysis decomposition of the current image. Interested readers should seek information about this methodology elsewhere (e.g. Google) or the DIPUM book from where this code was derived.
Copyright © <2010>, <Joaquim Luis>
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