FourierGaussFltImg

DESCRIPTION

Applies a Gaussian 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) = HF Gain + (DC Gain - HF Gain) * exp
          {-[(a11 u + a12 v)**2 + (a21 u + a22 v)**2 ]}
 
 

 H( )
 transfer function of the filter
 

 u,v
 2D frequency coordinates
 

 HF Gain
 gain of filter at the Nyquist frequency (highest).
 

 DC Gain
 gain of the filter at zero frequency (DC).
 

 Min Half
 frequency of half power point along the minor elliptical axis
 

 Maj Half
 frequency of half power point along the major elliptical axis
 

 Theta
 angle in degrees of the filter's orientation
 

 xSize
 x dimension of the source image
 

 ySize
 y dimension of the source image
 

 sigmaL
 sqrt (.693147/ (minHalf*minHalf))
 

 sigmaS
 sqrt (.693147/ (majHalf*majHalf))
 

 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: HF Gain
Type: Dial
HF Gain constant value

Port: DC Gain
Type: Dial
DC Gain constant value

Port: Min Half
Type: Dial
Min Half constant value

Port: Maj Half
Type: Dial
Maj Half constant value

Port: Theta
Type: Dial
Theta constant value

OUTPUTS

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

PROBLEMS