core/vil/algo/vil_orientations.h

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#ifndef vil_orientations_h_
#define vil_orientations_h_
//:
// \file
// \brief Functions to compute orientations and gradient magnitude
// \author Tim Cootes

#include <vil/vil_image_view.h>
#include <vxl_config.h>
#include <vil/algo/vil_sobel_3x3.h>

//: Compute orientation (in radians) and gradient magnitude at each pixel
//  Images assumed to be single plane
// \relatesalso vil_image_view
void vil_orientations(const vil_image_view<float>& grad_i,
                      const vil_image_view<float>& grad_j,
                      vil_image_view<float>& orient_im,
                      vil_image_view<float>& grad_mag);

//: Compute discrete orientation and gradient magnitude at each pixel
//  Computes orientation at each pixel and scales to range [0,n_orientations-1].
//
//  Orientation of i corresponds to angles in range [(i-0.5)dA,(i+0.5)dA]
//  where dA=2*pi/n_orientations.
//
//  Images assumed to be single plane
// \relatesalso vil_image_view
void vil_orientations(const vil_image_view<float>& grad_i,
                      const vil_image_view<float>& grad_j,
                      vil_image_view<vxl_byte>& orient_im,
                      vil_image_view<float>& grad_mag,
                      unsigned n_orientations=256);

//: Compute discrete orientation and gradient magnitude at edge pixels
//  Computes orientation at each pixel and scales to range [0,n_orientations].
//  If gradient magnitude is less than grad_threshold, then orientation
//  of zero is set, meaning undefined orientation.
//
//  Orientation of i>0 corresponds to angles in range [(i-1.5)dA,(i-0.5)dA]
//  where dA=2*pi/n_orientations.
//
//  Images assumed to be single plane
// \relatesalso vil_image_view
void vil_orientations_at_edges(const vil_image_view<float>& grad_i,
                               const vil_image_view<float>& grad_j,
                               vil_image_view<vxl_byte>& orient_im,
                               vil_image_view<float>& grad_mag,
                               float grad_threshold,
                               unsigned n_orientations=255);

//: Compute orientation and gradient magnitude using sobel to get gradients
// \relatesalso vil_image_view
template <class T>
inline void vil_orientations_from_sobel(const vil_image_view<T>& src_image,
                                        vil_image_view<float>& orient_im,
                                        vil_image_view<float>& grad_mag)
{
  vil_image_view<float> grad_i,grad_j;
  vil_sobel_3x3(src_image,grad_i,grad_j);
  vil_orientations(grad_i,grad_j,orient_im,grad_mag);
}

//: Compute discrete orientation and gradient using sobel operations
//  Computes orientation at each pixel and scales to range [0,n_orientations-1].
//
//  Orientation of i corresponds to angles in range [(i-0.5)dA,(i+0.5)dA]
//  where dA=2*pi/n_orientations.
//
//  Images assumed to be single plane
// \relatesalso vil_image_view
template <class T>
inline void vil_orientations_from_sobel(const vil_image_view<T>& src_image,
                                        vil_image_view<vxl_byte>& orient_im,
                                        vil_image_view<float>& grad_mag,
                                        unsigned n_orientations=256)
{
  vil_image_view<float> grad_i,grad_j;
  vil_sobel_3x3(src_image,grad_i,grad_j);
  vil_orientations(grad_i,grad_j,orient_im,grad_mag,n_orientations);
}

#endif // vil_orientations_h_