Image decorrelation

For these reasons the KLT is seldom used in practice. To circumvent these problems, sub-optimal basis transforms are employed which effectively decorrelate the image but are image-independent and have a reduced (linear or linear-log) time-complexity. 

The difference and transform compression schemes described above attempt to decorrelate the image data at a single resolution only. With the advent of multiresolution representations (pyramids, wavelet transforms, subband... 

Li PC, Li CY, Yeh WC (2002) Tissue motion and elevational speckle decorrelation in freehand 3D ultrasound. Ultra-son Imaging 24 1-12... 

Users of ASTER data have found decorrelation stretching to be particnlarly effective in image display. The stretch is effective whether the bands used are in the Visible, the SWIR, or the thermal IR interval. The three ASTER scenes in Fig. 11 (again, of an unidentified area) show the effects of a DS. 

Fig. 11 Decorrelation stretch of visible, SWIR and thermal IR images from ASTER...

Since speckle depends also on the frequency of the ultrasound beam, imaging modalities have been developed that use simultaneous emission of two different bands of frequencies instead of one to decorrelate speckle and improve the signal-to-noise ratio (Oktar et al. 2003). Some equipment allows for simultaneous use of both spatial and frequency compounding. 

Discrete cosine transformation (DCT) Decorrelates image data efficiently [Rao and Yip 1990]. 

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