slice3.cc

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/*    vspline - a set of generic tools for creation and evaluation      */
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/// \file slice3.cc
///
/// \brief create 2D image data from a 3D spline
///
/// build a 3D volume from samples of the RGB colour space
/// build a spline over it and extract a 2D slice
///
/// Here we use a quick shot solution.
/// Oftentimes all it takes is a single run of an interpolation with
/// as little programming effort as possible, never mind the performance.
/// Again we use a b-spline with double-precision voxels as value_type,
/// but instead of using vspline::transform, we simply run the calculations
/// in loops.
///
/// compile with:
/// clang++ -std=c++11 -o slice3 -O3 -pthread slice3.cc -lvigraimpex
/// g++ also works.
 
#include <iostream>
 
#include <vspline/vspline.h>
 
#include <vigra/stdimage.hxx>
#include <vigra/imageinfo.hxx>
#include <vigra/impex.hxx>
 
// voxel_type is the source data type
typedef vigra::RGBValue < double , 0 , 1 , 2 > voxel_type ;
 
// pixel_type is the result type, here we use a vigra::RGBValue for a change
typedef vigra::RGBValue < unsigned char , 0 , 1 , 2 > pixel_type ;
 
// coordinate_type has a 3D coordinate
typedef vigra::TinyVector < float , 3 > coordinate_type ;
 
int main ( int argc , char * argv[] )
{
  // we want a b-spline with natural boundary conditions
  vigra::TinyVector < vspline::bc_code , 3 > bcv ( vspline::NATURAL ) ;
  
  // create quintic 3D b-spline object containing voxels
  vspline::bspline < voxel_type , 3 >
    bspl ( vigra::Shape3 ( 10 , 10 , 10 ) , 5 , bcv ) ;
  
  // fill the b-spline's core with a three-way gradient
    
  for ( int z = 0 ; z < 10 ; z++ )
  {
    for ( int y = 0 ; y < 10 ; y++ )
    {
      for ( int x = 0 ; x < 10 ; x++ )
      {
        bspl.core ( x , y , z ) = voxel_type ( 25.5 * x , 25.5 * y , 25.5 * z ) ;
      }
    }
  }
  
  // prefilter the b-spline
  
  bspl.prefilter() ;
  
  // get an evaluator for the b-spline
  
  auto ev = vspline::make_evaluator ( bspl ) ;
  
  // this is where the result should go:
  
  vigra::MultiArray < 2 , pixel_type > target ( vigra::Shape2 ( 1920 , 1080 ) ) ;
 
  // we want the pick-up coordinates to follow this scheme:
  // pick ( x , y ) = ( x , 1 - x , y )
  // scaled appropriately
  
  for ( int y = 0 ; y < 1080 ; y++ )
  {
    for ( int x = 0 ; x < 1920 ; x++ )
    {
      // calculate the pick-up coordinate
      coordinate_type pick { x / 192.0f ,
                             10.0f - x / 192.0f ,
                             y / 108.0f } ;
      // call the evaluator and store the result to 'target'                   
      target ( x , y ) = ev ( pick ) ;
    }
  }
  
  // store the result with vigra impex
  vigra::ImageExportInfo imageInfo ( "slice.tif" );
  
  vigra::exportImage ( target ,
                      imageInfo
                      .setPixelType("UINT8")
                      .setCompression("100")
                      .setForcedRangeMapping ( 0 , 255 , 0 , 255 ) ) ;
  
  std::cout << "result was written to slice.tif" << std::endl ;
  exit ( 0 ) ;
}