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.help asisinit Dec98 "Image Interpolator Package"
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NAME
asisinit -- initialize the sequential interpolant descriptor using user parameters
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SYNOPSIS
include <math/iminterp.h>
asisinit (asi, interp_type, nsinc, nincr, rparam, badval)
.nf
pointer asi #O interpolant descriptor
int interp_type #I interpolant type
int nsinc #I sinc interpolant width in pixels
int nincr #I sinc look-up table resolution
real pixfrac #I sinc shift or drizzle pixel fraction
real badval #I drizzle undefined pixel value
.fi
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ARGUMENTS
.ls asi
Pointer to sequential interpolant descriptor.
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.ls interp_type
Interpolant type. The options are II_NEAREST, II_LINEAR, II_POLY3, II_POLY5,
II_SPLINE3, II_SINC, II_LSINC, and II_DRIZZLE for the nearest neighbour, linear,
3rd order polynomial, 5th order polynomial, cubic spline, sinc, look-up
table sinc, and drizzle interpolants respectively. The interpolant type
definitions are found in the package header file math/iminterp.h.
.le
.ls nsinc
The sinc and look-up table sinc interpolant width in pixels. Nsinc is
rounded up internally to the nearest odd number.
.le
.ls nincr
The look-up table sinc resolution in number of entries. Nincr = 10 implies
a pixel resolution of 0.1 pixels, nincr = 20 a pixel resolution of 0.05
pixels, etc.
.le
.ls pixfrac
The look-up table sinc fractional pixel shift if nincr = 1 in which case
-0.5 <= pixfrac <= 0.5 , or the drizzle pixel fraction in which case
0.0 <= pixfrac <= 1.0. A minimum value of 0.001 is imposed on pixfrac.
.le
.ls badval
The undefined pixel value for the drizzle interpolant. Pixels within
the boundaries of the input image which do not overlap the input image
pixels are assigned a value of badval.
.le
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DESCRIPTION
The interpolant descriptor is allocated and initialized. The pointer asi is
returned by ASISINIT.
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NOTES
ASIINIT or ASISINIT must be called before using any other ASI routines.
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SEE ALSO
asisinit, asifree
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