// Copyright (C) 2008 Davis E. King (davis@dlib.net)
// License: Boost Software License See LICENSE.txt for the full license.
#ifndef DLIB_EDGE_DETECTOr_
#define DLIB_EDGE_DETECTOr_
#include "edge_detector_abstract.h"
#include "../pixel.h"
#include "../array2d.h"
namespace dlib
{
// ----------------------------------------------------------------------------------------
template <
typename T
>
inline char edge_orientation (
const T& x_,
const T& y_
)
{
// if this is a perfectly horizontal gradient then return right away
if (x_ == 0)
{
return '|';
}
else if (y_ == 0) // if this is a perfectly vertical gradient then return right away
{
return '-';
}
// Promote x so that when we multiply by 128 later we know overflow won't happen.
typedef typename promote<T>::type type;
type x = x_;
type y = y_;
if (x < 0)
{
x = -x;
if (y < 0)
{
y = -y;
x *= 128;
const type temp = x/y;
if (temp > 309)
return '-';
else if (temp > 53)
return '/';
else
return '|';
}
else
{
x *= 128;
const type temp = x/y;
if (temp > 309)
return '-';
else if (temp > 53)
return '\\';
else
return '|';
}
}
else
{
if (y < 0)
{
y = -y;
x *= 128;
const type temp = x/y;
if (temp > 309)
return '-';
else if (temp > 53)
return '\\';
else
return '|';
}
else
{
x *= 128;
const type temp = x/y;
if (temp > 309)
return '-';
else if (temp > 53)
return '/';
else
return '|';
}
}
}
// ----------------------------------------------------------------------------------------
template <
typename in_image_type,
typename out_image_type
>
void sobel_edge_detector (
const in_image_type& in_img_,
out_image_type& horz_,
out_image_type& vert_
)
{
typedef typename image_traits<out_image_type>::pixel_type pixel_type;
COMPILE_TIME_ASSERT(pixel_traits<pixel_type>::is_unsigned == false);
DLIB_ASSERT( !is_same_object(in_img_,horz_) && !is_same_object(in_img_,vert_) &&
!is_same_object(horz_,vert_),
"\tvoid sobel_edge_detector(in_img_, horz_, vert_)"
<< "\n\t You can't give the same image as more than one argument"
<< "\n\t is_same_object(in_img_,horz_): " << is_same_object(in_img_,horz_)
<< "\n\t is_same_object(in_img_,vert_): " << is_same_object(in_img_,vert_)
<< "\n\t is_same_object(horz_,vert_): " << is_same_object(horz_,vert_)
);
const int vert_filter[3][3] = {{-1,-2,-1},
{0,0,0},
{1,2,1}};
const int horz_filter[3][3] = { {-1,0,1},
{-2,0,2},
{-1,0,1}};
const long M = 3;
const long N = 3;
const_image_view<in_image_type> in_img(in_img_);
image_view<out_image_type> horz(horz_);
image_view<out_image_type> vert(vert_);
horz.set_size(in_img.nr(),in_img.nc());
vert.set_size(in_img.nr(),in_img.nc());
assign_border_pixels(horz,1,1,0);
assign_border_pixels(vert,1,1,0);
// figure out the range that we should apply the filter to
const long first_row = M/2;
const long first_col = N/2;
const long last_row = in_img.nr() - M/2;
const long last_col = in_img.nc() - N/2;
// apply the filter to the image
for (long r = first_row; r < last_row; ++r)
{
for (long c = first_col; c < last_col; ++c)
{
typedef typename pixel_traits<typename image_traits<in_image_type>::pixel_type>::basic_pixel_type bp_type;
typename promote<bp_type>::type p, horz_temp, vert_temp;
horz_temp = 0;
vert_temp = 0;
for (long m = 0; m < M; ++m)
{
for (long n = 0; n < N; ++n)
{
// pull out the current pixel and put it into p
p = get_pixel_intensity(in_img[r-M/2+m][c-N/2+n]);
horz_temp += p*horz_filter[m][n];
vert_temp += p*vert_filter[m][n];
}
}
assign_pixel(horz[r][c] , horz_temp);
assign_pixel(vert[r][c] , vert_temp);
}
}
}
// ----------------------------------------------------------------------------------------
namespace impl
{
template <typename T>
typename promote<T>::type square (const T& a)
{
return static_cast<T>(a)*static_cast<T>(a);
}
}
template <
typename in_image_type,
typename out_image_type
>
void suppress_non_maximum_edges (
const in_image_type& horz_,
const in_image_type& vert_,
out_image_type& out_img_
)
{
const_image_view<in_image_type> horz(horz_);
const_image_view<in_image_type> vert(vert_);
image_view<out_image_type> out_img(out_img_);
COMPILE_TIME_ASSERT(is_signed_type<typename image_traits<in_image_type>::pixel_type>::value);
DLIB_ASSERT( horz.nr() == vert.nr() && horz.nc() == vert.nc(),
"\tvoid suppress_non_maximum_edges(horz, vert, out_img)"
<< "\n\tYou have to give horz and vert gradient images that are the same size"
<< "\n\thorz.nr(): " << horz.nr()
<< "\n\thorz.nc(): " << horz.nc()
<< "\n\tvert.nr(): " << vert.nr()
<< "\n\tvert.nc(): " << vert.nc()
);
DLIB_ASSERT( !is_same_object(out_img_,horz_) && !is_same_object(out_img_,vert_),
"\tvoid suppress_non_maximum_edges(horz_, vert_, out_img_)"
<< "\n\t out_img can't be the same as one of the input images."
<< "\n\t is_same_object(out_img_,horz_): " << is_same_object(out_img_,horz_)
<< "\n\t is_same_object(out_img_,vert_): " << is_same_object(out_img_,vert_)
);
using std::min;
using std::abs;
// if there isn't any input image then don't do anything
if (horz.size() == 0)
{
out_img.clear();
return;
}
out_img.set_size(horz.nr(),horz.nc());
zero_border_pixels(out_img,1,1);
// now do non maximum suppression while we copy the
const long M = 3;
const long N = 3;
// figure out the range that we should apply the filter to
const long first_row = M/2;
const long first_col = N/2;
const long last_row = horz.nr() - M/2;
const long last_col = horz.nc() - N/2;
// apply the filter to the image
for (long r = first_row; r < last_row; ++r)
{
for (long c = first_col; c < last_col; ++c)
{
typedef typename promote<typename image_traits<in_image_type>::pixel_type>::type T;
const T y = horz[r][c];
const T x = vert[r][c];
using impl::square;
const T val = square(horz[r][c]) + square(vert[r][c]);
const char ori = edge_orientation(x,y);
const unsigned char zero = 0;
switch (ori)
{
case '-':
if (square(horz[r-1][c])+square(vert[r-1][c]) > val || square(horz[r+1][c]) + square(vert[r+1][c]) > val)
assign_pixel(out_img[r][c] , zero);
else
assign_pixel(out_img[r][c] , std::sqrt((double)val));
break;
case '|':
if (square(horz[r][c-1]) + square(vert[r][c-1]) > val || square(horz[r][c+1]) + square(vert[r][c+1]) > val)
assign_pixel(out_img[r][c] , zero);
else
assign_pixel(out_img[r][c] , std::sqrt((double)val));
break;
case '/':
if (square(horz[r-1][c-1]) + square(vert[r-1][c-1]) > val || square(horz[r+1][c+1]) + square(vert[r+1][c+1]) > val)
assign_pixel(out_img[r][c] , zero);
else
assign_pixel(out_img[r][c] , std::sqrt((double)val));
break;
case '\\':
if (square(horz[r+1][c-1]) + square(vert[r+1][c-1]) > val || square(horz[r-1][c+1]) + square(vert[r-1][c+1]) > val)
assign_pixel(out_img[r][c] , zero);
else
assign_pixel(out_img[r][c] , std::sqrt((double)val));
break;
}
}
}
}
// ----------------------------------------------------------------------------------------
}
#endif // DLIB_EDGE_DETECTOr_