mksinc.cwp.lib

su 的源代码库

MKSINC - Compute least-squares optimal sinc interpolation coefficients.

mksinc		Compute least-squares optimal sinc interpolation coefficients.

Function Prototype:
void mksinc (float d, int lsinc, float sinc[]);

Input:
d		fractional distance to interpolation point; 0.0<=d<=1.0
lsinc		length of sinc approximation; lsinc%2==0 and lsinc<=20

Output:
sinc		array[lsinc] containing interpolation coefficients

Notes:
The coefficients are a least-squares-best approximation to the ideal
sinc function for frequencies from zero up to a computed maximum
frequency.  For a given interpolator length, lsinc, mksinc computes
the maximum frequency, fmax (expressed as a fraction of the nyquist
frequency), using the following empirically derived relation (from
a Western Geophysical Technical Memorandum by Ken Larner):

	fmax = min(0.066+0.265*log(lsinc),1.0)

Note that fmax increases as lsinc increases, up to a maximum of 1.0.
Use the coefficients to interpolate a uniformly-sampled function y(i) 
as follows:

            lsinc-1
    y(i+d) =  sum  sinc[j]*y(i+j+1-lsinc/2)
              j=0

Interpolation error is greatest for d=0.5, but for frequencies less
than fmax, the error should be less than 1.0 percent.

Author:  Dave Hale, Colorado School of Mines, 06/02/89