// Copyright (C) 2014 Davis E. King (davis@dlib.net) // License: Boost Software License See LICENSE.txt for the full license. #ifndef DLIB_HOUGH_tRANSFORM_Hh_ #define DLIB_HOUGH_tRANSFORM_Hh_ #include "hough_transform_abstract.h" #include "../image_processing/generic_image.h" #include "../geometry.h" #include "../algs.h" #include "assign_image.h" #include <limits> namespace dlib { // ---------------------------------------------------------------------------------------- class hough_transform { public: explicit hough_transform ( unsigned long size_ ) : _size(size_) { DLIB_CASSERT(size_ > 0, "\t hough_transform::hough_transform(size_)" << "\n\t Invalid arguments given to this function." ); even_size = _size - (_size%2); const point cent = center(rectangle(0,0,size_-1,size_-1)); xcos_theta.set_size(size_, size_); ysin_theta.set_size(size_, size_); std::vector<double> cos_theta(size_), sin_theta(size_); const double scale = 1<<16; for (unsigned long t = 0; t < size_; ++t) { double theta = t*pi/even_size; cos_theta[t] = scale*std::cos(theta)/sqrt_2; sin_theta[t] = scale*std::sin(theta)/sqrt_2; } const double offset = scale*even_size/4.0 + 0.5; for (unsigned long c = 0; c < size_; ++c) { const long x = c - cent.x(); for (unsigned long t = 0; t < size_; ++t) xcos_theta(c,t) = static_cast<int32>(x*cos_theta[t] + offset); } for (unsigned long r = 0; r < size_; ++r) { const long y = r - cent.y(); for (unsigned long t = 0; t < size_; ++t) ysin_theta(r,t) = static_cast<int32>(y*sin_theta[t] + offset); } } unsigned long size( ) const { return _size; } long nr( ) const { return _size; } long nc( ) const { return _size; } std::pair<point, point> get_line ( const point& p ) const { DLIB_ASSERT(rectangle(0,0,size()-1,size()-1).contains(p) == true, "\t pair<point,point> hough_transform::get_line(point)" << "\n\t Invalid arguments given to this function." << "\n\t p: " << p << "\n\t size(): " << size() ); // First we compute the radius measured in pixels from the center and the theta // angle in radians. typedef dlib::vector<double,2> vect; const rectangle box(0,0,size()-1,size()-1); const vect cent = center(box); double theta = p.x()-cent.x(); double radius = p.y()-cent.y(); theta = theta*pi/even_size; radius = radius*sqrt_2 + 0.5; // now make a line segment on the line. vect v1 = cent + vect(size()+1000,0) + vect(0,radius); vect v2 = cent - vect(size()+1000,0) + vect(0,radius); point p1 = rotate_point(cent, v1, theta); point p2 = rotate_point(cent, v2, theta); clip_line_to_rectangle(box, p1, p2); return std::make_pair(p1,p2); } template < typename image_type > point get_best_hough_point ( const point& p, const image_type& himg_ ) { const const_image_view<image_type> himg(himg_); DLIB_ASSERT(himg.nr() == size() && himg.nc() == size() && rectangle(0,0,size()-1,size()-1).contains(p) == true, "\t point hough_transform::get_best_hough_point()" << "\n\t Invalid arguments given to this function." << "\n\t himg.nr(): " << himg.nr() << "\n\t himg.nc(): " << himg.nc() << "\n\t size(): " << size() << "\n\t p: " << p ); typedef typename image_traits<image_type>::pixel_type pixel_type; COMPILE_TIME_ASSERT(pixel_traits<pixel_type>::grayscale == true); pixel_type best_val = std::numeric_limits<pixel_type>::min(); point best_point; const long max_n8 = (himg.nc()/8)*8; const long max_n4 = (himg.nc()/4)*4; const long r = p.y(); const long c = p.x(); const int32* ysin = &ysin_theta(r,0); const int32* xcos = &xcos_theta(c,0); long t = 0; while(t < max_n8) { long rr0 = (*xcos++ + *ysin++)>>16; long rr1 = (*xcos++ + *ysin++)>>16; long rr2 = (*xcos++ + *ysin++)>>16; long rr3 = (*xcos++ + *ysin++)>>16; long rr4 = (*xcos++ + *ysin++)>>16; long rr5 = (*xcos++ + *ysin++)>>16; long rr6 = (*xcos++ + *ysin++)>>16; long rr7 = (*xcos++ + *ysin++)>>16; if (himg[rr0][t++] > best_val) { best_val = himg[rr0][t-1]; best_point.x() = t-1; best_point.y() = rr0; } if (himg[rr1][t++] > best_val) { best_val = himg[rr1][t-1]; best_point.x() = t-1; best_point.y() = rr1; } if (himg[rr2][t++] > best_val) { best_val = himg[rr2][t-1]; best_point.x() = t-1; best_point.y() = rr2; } if (himg[rr3][t++] > best_val) { best_val = himg[rr3][t-1]; best_point.x() = t-1; best_point.y() = rr3; } if (himg[rr4][t++] > best_val) { best_val = himg[rr4][t-1]; best_point.x() = t-1; best_point.y() = rr4; } if (himg[rr5][t++] > best_val) { best_val = himg[rr5][t-1]; best_point.x() = t-1; best_point.y() = rr5; } if (himg[rr6][t++] > best_val) { best_val = himg[rr6][t-1]; best_point.x() = t-1; best_point.y() = rr6; } if (himg[rr7][t++] > best_val) { best_val = himg[rr7][t-1]; best_point.x() = t-1; best_point.y() = rr7; } } while(t < max_n4) { long rr0 = (*xcos++ + *ysin++)>>16; long rr1 = (*xcos++ + *ysin++)>>16; long rr2 = (*xcos++ + *ysin++)>>16; long rr3 = (*xcos++ + *ysin++)>>16; if (himg[rr0][t++] > best_val) { best_val = himg[rr0][t-1]; best_point.x() = t-1; best_point.y() = rr0; } if (himg[rr1][t++] > best_val) { best_val = himg[rr1][t-1]; best_point.x() = t-1; best_point.y() = rr1; } if (himg[rr2][t++] > best_val) { best_val = himg[rr2][t-1]; best_point.x() = t-1; best_point.y() = rr2; } if (himg[rr3][t++] > best_val) { best_val = himg[rr3][t-1]; best_point.x() = t-1; best_point.y() = rr3; } } while(t < himg.nc()) { long rr0 = (*xcos++ + *ysin++)>>16; if (himg[rr0][t++] > best_val) { best_val = himg[rr0][t-1]; best_point.x() = t-1; best_point.y() = rr0; } } return best_point; } template < typename in_image_type, typename out_image_type > void operator() ( const in_image_type& img_, const rectangle& box, out_image_type& himg_ ) const { typedef typename image_traits<in_image_type>::pixel_type in_pixel_type; typedef typename image_traits<out_image_type>::pixel_type out_pixel_type; DLIB_CASSERT(box.width() == size() && box.height() == size(), "\t hough_transform::hough_transform(size_)" << "\n\t Invalid arguments given to this function." << "\n\t box.width(): " << box.width() << "\n\t box.height(): " << box.height() << "\n\t size(): " << size() ); COMPILE_TIME_ASSERT(pixel_traits<in_pixel_type>::grayscale == true); COMPILE_TIME_ASSERT(pixel_traits<out_pixel_type>::grayscale == true); const_image_view<in_image_type> img(img_); image_view<out_image_type> himg(himg_); himg.set_size(size(), size()); assign_all_pixels(himg, 0); const rectangle area = box.intersect(get_rect(img)); const long max_n8 = (himg.nc()/8)*8; const long max_n4 = (himg.nc()/4)*4; for (long r = area.top(); r <= area.bottom(); ++r) { const int32* ysin_base = &ysin_theta(r-box.top(),0); for (long c = area.left(); c <= area.right(); ++c) { const out_pixel_type val = static_cast<out_pixel_type>(img[r][c]); if (val != 0) { /* // The code in this comment is equivalent to the more complex but // faster code below. We keep this simple version of the Hough // transform implementation here just to document what it's doing // more clearly. const point cent = center(box); const long x = c - cent.x(); const long y = r - cent.y(); for (long t = 0; t < himg.nc(); ++t) { double theta = t*pi/even_size; double radius = (x*std::cos(theta) + y*std::sin(theta))/sqrt_2 + even_size/2 + 0.5; long rr = static_cast<long>(radius); himg[rr][t] += val; } continue; */ // Run the speed optimized version of the code in the above // comment. const int32* ysin = ysin_base; const int32* xcos = &xcos_theta(c-box.left(),0); long t = 0; while(t < max_n8) { long rr0 = (*xcos++ + *ysin++)>>16; long rr1 = (*xcos++ + *ysin++)>>16; long rr2 = (*xcos++ + *ysin++)>>16; long rr3 = (*xcos++ + *ysin++)>>16; long rr4 = (*xcos++ + *ysin++)>>16; long rr5 = (*xcos++ + *ysin++)>>16; long rr6 = (*xcos++ + *ysin++)>>16; long rr7 = (*xcos++ + *ysin++)>>16; himg[rr0][t++] += val; himg[rr1][t++] += val; himg[rr2][t++] += val; himg[rr3][t++] += val; himg[rr4][t++] += val; himg[rr5][t++] += val; himg[rr6][t++] += val; himg[rr7][t++] += val; } while(t < max_n4) { long rr0 = (*xcos++ + *ysin++)>>16; long rr1 = (*xcos++ + *ysin++)>>16; long rr2 = (*xcos++ + *ysin++)>>16; long rr3 = (*xcos++ + *ysin++)>>16; himg[rr0][t++] += val; himg[rr1][t++] += val; himg[rr2][t++] += val; himg[rr3][t++] += val; } while(t < himg.nc()) { long rr0 = (*xcos++ + *ysin++)>>16; himg[rr0][t++] += val; } } } } } private: unsigned long _size; unsigned long even_size; // equal to _size if _size is even, otherwise equal to _size-1. matrix<int32> xcos_theta, ysin_theta; }; } #endif // DLIB_HOUGH_tRANSFORM_Hh_