one_channel_filter

 one_channel_filter (hdi,hdo,U0, V0, 
             theta, Sigma1, Sigma2, 
             SigmaLP, alpha, filter, 
             nonlin, blurr, twoangle)
      struct header *hdi, *hdo;
      double U0, V0, theta, Sigma1, 
             Sigma2, SigmaLP, alpha;      
      int filter, nonlin, blurr;         
      Boolean twoangle;

• Input image
• Output image
• Vert. centre frequency
• Horz. centre frequency
• Rotation of filter
• Vert. sigma for filter
• Horz. sigma for filter
• Sigma for low-pass `feature' filter
• Alpha in tanh(..) nonlinearity
• Filter type identifier (NO_FILTER, GENERAL_GABOR or EVEN_GABOR)
• Nonlinearity identifier (NO_NONLIN or TANH_NONLIN)
• Blurring identifier (blurring=lowpass filtering) (NO_BLURR or BLURR)
• Use both positive and negative angle? If true, then the frequeny responses of both the Gabor filter with +theta angle and theta+90 degrees angles will be added to form one frequency response of the filter. Remember that filtering is performed by multiplication in the Fourier domain.