vil_greyscale_erode.h

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#ifndef vil_greyscale_erode_h_
#define vil_greyscale_erode_h_
//:
// \file
// \brief Perform greyscale erosion on images
// \author Tim Cootes

#include <vil/algo/vil_structuring_element.h>
#include <vil/vil_image_view.h>

//: Return minimum value of im[offset[k]]
template <class T>
inline T vil_greyscale_erode(const T* im, const std::ptrdiff_t* offset, unsigned n)
{
  T min_v = im[offset[0]];
  for (unsigned i=1;i<n;++i)
    if (im[offset[i]]<min_v) min_v=im[offset[i]];
  return min_v;
}

//: Return max of pixels under structuring element centred at (i0,j0)
//  Checks boundary overlap
// \relatesalso vil_image_view
// \relatesalso vil_structuring_element
template <class T>
inline T vil_greyscale_erode(const vil_image_view<T>& image, unsigned plane,
                             const vil_structuring_element& element,
                             int i0, int j0)
{
  T min_v = T(0); // dummy initialisation - otherwise, compiler complains
  bool first=true;
  unsigned n = element.p_i().size();
  for (unsigned int k=0;k<n;++k)
  {
    unsigned int i = i0+element.p_i()[k];
    unsigned int j = j0+element.p_j()[k];
    if (i<image.ni() && j<image.nj())
    {
      if (first || image(i,j,plane) < min_v) {
        min_v=image(i,j,plane); first=false; }
    }
  }
  return min_v;
}

//: Erodes src_image to produce dest_image (assumed single plane).
// dest_image(i0,j0) is the minimum value of the pixels under the
// structuring element when it is centred on src_image(i0,j0)
// \relatesalso vil_image_view
// \relatesalso vil_structuring_element
template <class T>
void vil_greyscale_erode(const vil_image_view<T>& src_image,
                         vil_image_view<T>& dest_image,
                         const vil_structuring_element& element);

#endif // vil_greyscale_erode_h_