quickstart.cc

Go to the documentation of this file.

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/*    vspline - a set of generic tools for creation and evaluation      */
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/// \file quickstart.cc
///
/// \brief sample code from the documentation
///
/// just the bits of code given in the 'Quickstart' section of the
/// documentation overview
///
/// compile: clang++ -std=c++11 -o quickstart -pthread quickstart.cc
 
#include <vspline/vspline.h>
#include <iostream>
#include <iomanip>
 
using namespace std ;
using namespace vigra ;
using namespace vspline ;
 
int main ( int argc , char * argv[] )
{
  // given a vigra::MultiArray of data
 
  vigra::MultiArray < 2 , float > a ( 10 , 20 ) ;
 
  // let's initialize the whole array with 42
 
  a = 42 ;
 
  typedef vspline::bspline < float , 2 > spline_type ; // fix the type of the spline
  
  spline_type bspl ( a.shape() ) ; // create bspline object 'bspl' suitable for your data
  
  bspl.core = a ;         // copy the source data into the bspline object's 'core' area
  
  bspl.prefilter() ; // run prefilter() to convert original data to b-spline coefficients
 
  // for a 2D spline, we want 2D coordinates
  
  typedef vigra::TinyVector < float , 2 > coordinate_type ;
  
  // get the appropriate evaluator type
  
  typedef vspline::evaluator < coordinate_type , float > eval_type ;
  
  // create the evaluator
  
  eval_type ev ( bspl ) ;
 
  // create variables for input and output: 
 
  float x = 3 , y = 4 ;
  coordinate_type coordinate ( x , y ) ;
  float result ;
 
  // use the evaluator to produce the result
 
  ev.eval ( coordinate , result ) ; // evaluate at (x,y)
 
  auto r = ev ( coordinate ) ;     // alternative evaluation as a functor
 
  assert ( r == result ) ;
 
  // create a 1D array containing (2D) coordinates into 'a'
 
  vigra::MultiArray < 1 , coordinate_type > coordinate_array ( 3 ) ;
 
  // we initialize the coordinate array by hand...
 
  coordinate_array[0] = coordinate_array[1] = coordinate_array[2] = coordinate ;
 
  // create an array to accomodate the result of the remap operation
 
  vigra::MultiArray < 1 , float > target_array ( 3 ) ;
  
  // perform the remap
 
  vspline::remap ( a , coordinate_array , target_array ) ;
 
  auto ic = coordinate_array.begin() ;
  for ( auto k : target_array )
    assert ( k == ev ( *(ic++) ) ) ;
 
  // instead of the remap, we can use transform, passing the evaluator for
  // the b-spline over 'a' instead of 'a' itself. the result is the same.
 
  vspline::transform ( ev , coordinate_array , target_array ) ; 
 
  // create a 2D array for the index-based transform operation
 
  vigra::MultiArray < 2 , float > target_array_2d ( 3 , 4 ) ;
 
  // use transform to evaluate the spline for the coordinates of
  // all values in this array
 
  vspline::transform ( ev , target_array_2d ) ;
 
  for ( int x = 0 ; x < 3 ; x ++ )
  {
    for ( y = 0 ; y < 4 ; y++ )
    {
      coordinate_type c { float(x) , float(y) } ;
      assert ( target_array_2d [ c ] == ev ( c ) ) ;
    }
  }
 
  vigra::MultiArray < 2 , float > b ( 10 , 20 ) ;
  vspline::transform ( ev , b ) ;
 
  auto ia = a.begin() ;
  for ( auto r : b )
    assert ( vigra::closeAtTolerance ( *(ia++) , r , .00001 ) ) ;
  
  vigra::MultiArray < 2 , float > c ( 10 , 20 ) ;
  vspline::restore ( bspl , c ) ; // TODO: problem with g++
  
  auto ib = b.begin() ;
  for ( auto & ic : c )
    assert ( vigra::closeAtTolerance ( *(ib++) , ic , .00001 ) ) ;
}