iir.cc

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/*    vspline - a set of generic tools for creation and evaluation      */
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/// \file iir.cc
///
/// \brief  apply a forward/backward n-pole recursive filter to an image
///
/// vspline has some code which isn't useful only for b-splines.
/// One example is the application of a filter to a MultiArrayView.
/// With vspline's multithreaded SIMD code, this is done efficiently.
/// This example program will apply an n-pole forward/backward
/// recursive filter with the given pole values along the horizontal
/// and vertical. You can pass an arbitrarily long sequence of pole
/// values after an image file name, but bear in mind that some pole
/// values can lead to infinite results.
///
/// compile with:
/// ./examples.sh iir.cc
///
/// invoke passing an image file and the pole values. the result
/// will be written to 'iir.tif'
///
/// positive pole values will blur the image. Don't exceed 1.0.
/// Negative values will sharpen the image. blurring with a single
/// positive pole value close to 1.0 is a very efficient way to affect
/// a strong blur quickly.
///
/// TODO: compare the result of this filter with a standard gaussian
 
#include <iostream>
#include <stdlib.h>
 
#include <vspline/general_filter.h>
 
#include <vigra/stdimage.hxx>
#include <vigra/imageinfo.hxx>
#include <vigra/impex.hxx>
 
// we silently assume we have a colour image
 
typedef vigra::RGBValue < float , 0 , 1 , 2 > pixel_type; 
 
// target_type is a 2D array of pixels  
 
typedef vigra::MultiArray < 2 , pixel_type > target_type ;
 
int main ( int argc , char * argv[] )
{
  if ( argc < 2 )
  {
    std::cerr << "pass a colour image file as argument," << std::endl ;
    std::cerr << "followed by the pole value(s)" << std::endl ;
    exit( -1 ) ;
  }
 
  // get the image file name
  
  vigra::ImageImportInfo imageInfo ( argv[1] ) ;
 
  std::vector < vspline::xlf_type > kernel ;
  char * end ;
 
  for ( int i = 2 ; i < argc ; i++ )
    kernel.push_back ( vspline::xlf_type ( strtold ( argv [ i ] , &end ) ) ) ;
 
  // create an array for the image data
  
  target_type image ( imageInfo.shape() ) ;
  
  // load the image data
                   
  vigra::importImage ( imageInfo , image ) ;
  
  // apply the filter
 
  vspline::forward_backward_recursive_filter
   ( image ,
     image ,
     { vspline::MIRROR , vspline::MIRROR } ,
     kernel ,
     kernel.size() / 2 ) ;
 
  // store the result with vigra impex
 
  vigra::ImageExportInfo eximageInfo ( "iir.tif" );
  
  std::cout << "storing the target image as 'iir.tif'" << std::endl ;
  
  vigra::exportImage ( image ,
                       eximageInfo
                       .setPixelType("UINT8") ) ;
  
  exit ( 0 ) ;
}