IMAGE commands
PROGRAM NAME
ilpf - 2-Dimensional Low-Pass Filter Design
DESCRIPTION
This routine generates a spatial frequency image of real values
that represents the response of a Low-Pass Filter.
The generator function brands are Ideal, Butterworth, Gaussian,
Chebyshev I, and Chebyshev II. The output is radially
symmetric across the origin of the image, and the origin can
be either the center of the image or the top left corner
of the image. Cutoff frequencies are normalized between
0 and 1.0 where 0 is DC, and 1.0 is the Nyquist frequency.
The filters are all radially symmetric across an origin that can be located
at pixel (0,0) or at (image_width/2, image_height/2). If image_height and
image_width are not the same value, the distance formula will normalize
the distance from the origin in a manner similar to this formula.
d = sqrt[(x/image_width)^2 + (y/image_height)^2]
This implies that a non-square image will produce an ellipse frequency image
as a result.
All filter types (Low-Pass, High-Pass, Band-Pass, and Band-Stop) use the
Low-Pass transfer function and a frequency transform formula on the
distance returned by the formula above (References listed below).
REQUIRED ARGUMENTS
- -o
-
type: outfile
desc: Output image
Mutually Exclusive Group; you must specify ONE of:
- -ideal
-
type: flag
desc: Ideal transfer response
OR
- -but
-
type: flag
desc: Butterworth transfer response
OR
- -gauss
-
type: flag
desc: Gaussian transfer response
OR
- -ch1
-
type: flag
desc: Chebyshev I transfer response
OR
- -ch2
-
type: flag
desc: Chebyshev II transfer response
OPTIONAL ARGUMENTS
- -pos
-
type: cycle
desc: Low frequencies located at image center or corners
default: 1 "Center of Image"
- -type
-
type: cycle
desc: Data type for output image
default: 11 "Double"
- -order
-
type: integer
desc: Order of filter to generate
default: 1
bounds: value >= 0
- -ucutoff
-
type: double
desc: Normalized upper cutoff frequency
default: 0.25
bounds: 0 < [-ucutoff] < 0.5
- -eps
-
type: double
desc: Ripple parameter (Chebyshev only)
default: 0.5
bounds: 0 < [-eps] < 1
- -hsize
-
type: integer
desc: The height size of the output filter
default: 256
bounds: value > 0
- -wsize
-
type: integer
desc: The width size of the output filter
default: 256
bounds: value > 0
EXAMPLES
None
SEE ALSO
ifiltdesign, lifiltdesign, kimage_proc
RESTRICTIONS
None
REFERENCES
Alan V. Oppenheim and Ronald W. Schafer, "Discrete-Time Signal Processing",
ISBN 0-13-216292-X, Prentice-Hall, 1989.
Edward P. Cunningham,"Digital Filtering: An Introduction", ISBN 0-395-53989-7,
Houghton Mifflin, 1992.
COPYRIGHT
Copyright (C) 1993 - 1997, Khoral Research, Inc. ("KRI") All rights reserved.