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fhamming

$ \bigcirc$Name


fhamming Apply Hamming window to a Fimage




$ \bigcirc$Command Synopsis


fhamming in out



in : input Fimage

out : windowed Fimage




$ \bigcirc$Function Summary


void fhamming (in , out )

Fimage in , out ;




$ \bigcirc$Description


This module applies a multiplicative mask on a Fimage u(x, y), called the Hamming window. If u is defined on [- a, a]×[- b, b], the result is given by

u'(x, y) = u(x, y).$\displaystyle \left(\vphantom{ \alpha + (1-\alpha) \cos \frac{\pi x}{a} }\right.$$\displaystyle \alpha$ + (1 - $\displaystyle \alpha$)cos$\displaystyle {\frac{{\pi x}}{{a}}}$$\displaystyle \left.\vphantom{ \alpha + (1-\alpha) \cos \frac{\pi x}{a} }\right)$$\displaystyle \left(\vphantom{ \alpha + (1-\alpha) \cos \frac{\pi y}{b} }\right.$$\displaystyle \alpha$ + (1 - $\displaystyle \alpha$)cos$\displaystyle {\frac{{\pi y}}{{b}}}$$\displaystyle \left.\vphantom{ \alpha + (1-\alpha) \cos \frac{\pi y}{b} }\right)$,

where $ \alpha$ = 0.54. Applying this operator to a non-periodic image before computing its Fourier Transform results in a better frequency estimation, since the high energy of the vertical and horizontal frequencies (due to the border's gap of the image) are cancelled.

cm

NB: Calling this C-subroutine with out = in is possible




$ \bigcirc$See Also


fft2dview.


$ \bigcirc$Version 1.0


Last Modification date : Thu Nov 29 20:23:56 2001


$ \bigcirc$Author


Lionel Moisan






next up previous contents index
Next: frandphase Up: Reference Previous: fftzoom   Contents   Index
mw 2004-05-05