IMAGE commands


PROGRAM NAME

ihpf - 2-Dimensional High-Pass Filter Design

DESCRIPTION

This routine generates a spatial frequency image of real values that represents the response of a High-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
-lcutoff
type: double
desc: Normalized lower cutoff frequency
default: 0.25
bounds: 0 < [-lcutoff] < 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.