fht2d
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Name
fht2d - 2 dimensional fast Hartley transform
Syntax
#include <xite/fht.h>
BiffStatus fht2d( IR_BAND inband,
IR_BAND outband, int forward );
Description
fht2d performs 2 dimensional fast Hartley transform,
forward transform if forward is true, inverse transform
otherwise.
The forward and inverse discrete Hartley transforms
are given respectively as:
M N
H(u,v) = Sum Sum f(x,y) [cas(2*Pi(u*x/M + v*y/N))]
x=0 y=0
M N
f(x,y) = Sum Sum H(u,v) [cas(2*Pi(u*x/M + v*y/N))]
x=0 y=0
where
cas(x) = cos(x) + sin(x)
The relationships between the Fourier and Hartley transforms
are described in the documentation of ht2ft(3) and
ft2ht(3).
For a description of how to use Hartley transforms to
accomplish convolution, refer to fht2d(1).
Restrictions
Only real pixels are accepted as input and output.
Input and output bands should be of equal size and be
some power of two.
References
-
[1] Mark A. ONeill
- "Faster than Fast Fourier",
BYTE, pp 293-300, April 1988
-
[2] R. N. Bracewell
- "The Hartley Transform",
Oxford Univ. Press 1986,
ISBN 0-19-503969-6
See also
fht2d(1), fft2d(3), haar2d(3), fht1d(3), fhtInitTables(3),
fhtPower(3), fhtPhase(3), ht2ft(3), ft2ht(3)
Return value
0 => ok
1 => bad input pixel type
2 => bad output pixel type
3 => band size is not power of two
4 => bands are not of equal size
5 => error in copyBand()
Author
Tor Lønnestad, BLAB, Ifi, UiO
Revised
Svein Bøe, BLAB, Ifi, UiO
Id
$Id: fht2d.c,v 1.31 1997/05/27 14:48:35 svein Exp $