FourierExpFltImg

DESCRIPTION

Applies an exponential frequency domain filter to a frequency domain image. The effect is to convolve a filter with the image in the spatial domain. The frequency domain representation of the filter is as follows:

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

FourierExpFltImg

DESCRIPTION

INPUTS

WIDGETS

OUTPUTS

PROBLEMS

SEE ALSO