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/************************************************************************/
/* */
/* vspline - a set of generic tools for creation and evaluation */
/* of uniform b-splines */
/* */
/* Copyright 2015 - 2023 by Kay F. Jahnke */
/* */
/* Permission is hereby granted, free of charge, to any person */
/* obtaining a copy of this software and associated documentation */
/* files (the "Software"), to deal in the Software without */
/* restriction, including without limitation the rights to use, */
/* copy, modify, merge, publish, distribute, sublicense, and/or */
/* sell copies of the Software, and to permit persons to whom the */
/* Software is furnished to do so, subject to the following */
/* conditions: */
/* */
/* The above copyright notice and this permission notice shall be */
/* included in all copies or substantial portions of the */
/* Software. */
/* */
/* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND */
/* EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES */
/* OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND */
/* NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT */
/* HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, */
/* WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING */
/* FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR */
/* OTHER DEALINGS IN THE SOFTWARE. */
/* */
/************************************************************************/
/// \file impulse_response.cc
///
/// \brief get the impulse response of a b-spline prefilter
///
/// filter a unit pulse with a b-spline prefilter of a given degree
/// and display the central section of the result
///
/// compile with:
/// clang++ -std=c++11 -o impulse_response -O3 -pthread impulse_response.cc
///
/// to get the central section with values beyond +/- 0.0042 of a degree 5 b-spline:
///
/// impulse_response 5 .0042
///
/// producing this output:
///
/// long double ir_5[] = {
/// -0.0084918610197410 ,
/// +0.0197222540252632 ,
/// -0.0458040841925519 ,
/// +0.1063780046433000 ,
/// -0.2470419274022756 ,
/// +0.5733258709616592 ,
/// -1.3217294729875093 ,
/// +2.8421709220216247 ,
/// -1.3217294729875098 ,
/// +0.5733258709616593 ,
/// -0.2470419274022757 ,
/// +0.1063780046433000 ,
/// -0.0458040841925519 ,
/// +0.0197222540252632 ,
/// -0.0084918610197410 ,
/// } ;
///
/// which, when used as a convolution kernel, will have the same effect on a signal
/// as applying the recursive filter itself, but with lessened precision due to windowing.
#include <iostream>
#include <iomanip>
#include <assert.h>
#include <vspline/multithread.h>
#include <vspline/vspline.h>
int main ( int argc , char * argv[] )
{
if ( argc < 3 )
{
std::cerr << "please pass spline degree and cutoff on the command line"
<< std::endl ;
exit ( -1 ) ;
}
int degree = std::atoi ( argv[1] ) ;
assert ( degree >= 0 && degree <= vspline_constants::max_degree ) ;
long double cutoff = std::atof ( argv[2] ) ;
std::cout << "calculating impulse response with spline degree "
<< degree << " and cutoff " << cutoff << std::endl ;
// using the highest-level access to prefiltering, we code:
vspline::bspline < long double , 1 > bsp ( 1001 , degree ) ;
auto v1 = bsp.core ;
v1 [ 500 ] = 1.0 ;
bsp.prefilter() ;
std::cout << "long double ir_" << degree << "[] = {" << std::endl ;
std::cout << std::fixed << std::showpoint
<< std::setprecision(std::numeric_limits<long double>::max_digits10) ;
for ( int k = 0 ; k < 1001 ; k++ )
{
if ( std::abs ( v1[k] ) > cutoff )
{
std::cout << v1[k] << "L ," << std::endl ;
}
}
std::cout << "} ;" << std::endl ;
}
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