FourierExpFltImg

DESCRIPTION

 H(u,v) = Alpha + Beta * exp {Gamma*[   (a11 u + a12 v)**2
             + (a21 u + a22 v)**2 ]}

where

 H( )   = transfer function of the filter
 u,v    = 2D frequency coordinates
 Alpha  = high frequency asymptote
 Beta   = decay coefficient
 Gamma  = exponential decay coefficient
 Eccent = Eccentricity of equal contours of the filter in the frequency domain
 Theta  = angle in degrees of the filter's orientation
 xSize  = x dimension of the source image
 ySize  = y dimension of the source image
 sigmaL = 1/ sqrt (1 -(Eccent*Eccent))
 sigmaS = 1.0
 phi    = 0.017453 * Theta
 a11    =  sigmaS * cos(phi) /xSize
 a12    =  sigmaS * sin(phi) /ySize
 a21    = -sigmaL * sin(phi) /xSize
 a22    =  sigmaL * cos(phi) /ySize

The input must be a frequency domain image in the packed format produced by the ForwardFFTImg module (see format description in ForwardFFTImg documentation). The Fourier transformation and the cross correlation are discussed in:

Digital Image Processing, Gonzales, R.C., Wintz, P., Addison Wesley, Second Edition, 1987, pp 61--137.

INPUTS

Port: Img In
Type: Lattice
Constraints: 1..3-D
source frequency domain image

WIDGETS

Port: Alpha
Type: Dial
Alpha constant value

Port: Beta
Type: Dial
Beta constant value

Port: Gamma
Type: Dial
Gamma constant value

Port: Eccent
Type: Dial
Eccent constant value

Port: Theta
Type: Dial
Theta constant value

OUTPUTS

Port: Img Out
Type: Lattice
Constraints: 1..3-D
filtered frequency domain image

PROBLEMS

SEE ALSO