Wavelet for multidimensional signals analysis: Difference between revisions

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{{=}} &psi;(x)<sub>h</sub>&psi;(y)<sub>h</sub> - &psi;(x)<sub>g</sub>&psi;(x)<sub>g</sub> + j [&psi;(x)<sub>h</sub>&psi;(y)<sub>g</sub> - &psi;(x)<sub>h</sub>&psi;(x)<sub>g</sub>]}}
 
The support of the Fourier spectrum of the wavelet above resides in first quadrant as in the diagram. When just the real part is considered, {{math|Real(&psi;(x,y)) {{=}} &psi;(x)<sub>h</sub>&psi;(y)<sub>h</sub> - &psi;(x)<sub>g</sub>&psi;(x)<sub>g</sub>}} has support on opposite quadrants (see figure in (a)). Both {{math|&psi;(x)<sub>h</sub>&psi;(y)<sub>h</sub>}} and {{math|&psi;(x)<sub>g</sub>&psi;(y)<sub>g</sub>}} correspond to HH subband of two different separable 2-D DWTs. This wavelet is oriented at {{math|-45<sup>o</sup>}}.
 
Similarly, by considering {{math| &psi;<sub>2</sub>(x,y) {{=}} &psi;(x)&psi;(y)<sup>*</sup>}}, wavelet oriented at {{math|45<sup>o</sup>}} is obtained. To obtain 4 more oriented real wavelets, {{math|&phi;(x)&psi;(y)}}, {{math|&psi;(x)&phi;(y)}}, {{math|&phi;(x)&psi;(y)<sup>*</sup>}} and {{math|&psi;(x)&phi;(y)<sup>*</sup>}} are considered.