IMAGE (kimage_proc) functions


LIBRARY ROUTINE

lifiltdesign - generate 2-dimensional frequency filter

LIBRARY CALL

int
lifiltdesign(
   int	    type,
   int	    brand,
   int	    order,
   int	    image_height,
   int	    image_width,
   double   lower_cutoff,
   double   upper_cutoff,
   double   epsilon,
   int	    centered,
   kobject  freq_image)

INPUT

OUTPUT

RETURN VALUE

TRUE (1) on success, FALSE (0) on failure

DESCRIPTION

This routine generates a spatial frequency image of real values (zero phase) that represent the magnitude response of the requested filter type and brand. The filter types are are: lowpass, highpass, bandpass, and bandstop. The function brands are: ideal, Butterworth, Gaussian, Chebyshev I, and Chebyshev II.

The output is symmetric across a diameter through the origin of the image; the origin can be either the center of the image or the top left corner of the image. Cutoff frequencies are normalized to the Nyquist frequency, thus implying that 0 corresponds to DC and 1.0 corresponds to the Nyquist frequency.

Note that the number of pixels between DC and Nyquist is given by the image_width/2 in the width direction and image_height/2 in the height direction. This means that if you ask for a non-square image you will get a non-circularly symmetric image passband in the output. This occurs because it is assumed that the frequency sampling interval is the same in both directions.

ADDITIONAL INFORMATION

none

EXAMPLES

none

SIDE EFFECTS

none

RESTRICTIONS

none

MODIFICATION

none

FILES

$IMAGE/objects/library/kimage_proc/src/lifiltdesign.c

SEE ALSO

kimage_proc(3)

COPYRIGHT

Copyright (C) 1993 - 1997, Khoral Research, Inc. ("KRI") All rights reserved.