OpenCV  4.5.2
Open Source Computer Vision
Public Member Functions | List of all members
cv::ximgproc::FastLineDetector Class Referenceabstract

Class implementing the FLD (Fast Line Detector) algorithm described in [137] . More...

#include <opencv2/ximgproc/fast_line_detector.hpp>

Inheritance diagram for cv::ximgproc::FastLineDetector:
cv::Algorithm

Public Member Functions

virtual ~FastLineDetector ()
 
virtual void detect (InputArray _image, OutputArray _lines)=0
 Finds lines in the input image. This is the output of the default parameters of the algorithm on the above shown image. More...
 
virtual void drawSegments (InputOutputArray _image, InputArray lines, bool draw_arrow=false)=0
 Draws the line segments on a given image. More...
 
- Public Member Functions inherited from cv::Algorithm
 Algorithm ()
 
virtual ~Algorithm ()
 
virtual void clear ()
 Clears the algorithm state. More...
 
virtual bool empty () const
 Returns true if the Algorithm is empty (e.g. in the very beginning or after unsuccessful read. More...
 
virtual String getDefaultName () const
 
virtual void read (const FileNode &fn)
 Reads algorithm parameters from a file storage. More...
 
virtual void save (const String &filename) const
 
void write (const Ptr< FileStorage > &fs, const String &name=String()) const
 simplified API for language bindings This is an overloaded member function, provided for convenience. It differs from the above function only in what argument(s) it accepts. More...
 
virtual void write (FileStorage &fs) const
 Stores algorithm parameters in a file storage. More...
 

Additional Inherited Members

- Static Public Member Functions inherited from cv::Algorithm
template<typename _Tp >
static Ptr< _Tpload (const String &filename, const String &objname=String())
 Loads algorithm from the file. More...
 
template<typename _Tp >
static Ptr< _TploadFromString (const String &strModel, const String &objname=String())
 Loads algorithm from a String. More...
 
template<typename _Tp >
static Ptr< _Tpread (const FileNode &fn)
 Reads algorithm from the file node. More...
 
- Protected Member Functions inherited from cv::Algorithm
void writeFormat (FileStorage &fs) const
 

Detailed Description

Class implementing the FLD (Fast Line Detector) algorithm described in [137] .

#include <iostream>
using namespace std;
using namespace cv;
using namespace cv::ximgproc;
int main(int argc, char** argv)
{
string in;
CommandLineParser parser(argc, argv, "{@input|corridor.jpg|input image}{help h||show help message}");
if (parser.has("help"))
{
parser.printMessage();
return 0;
}
in = samples::findFile(parser.get<string>("@input"));
Mat image = imread(in, IMREAD_GRAYSCALE);
if( image.empty() )
{
return -1;
}
// Create FLD detector
// Param Default value Description
// length_threshold 10 - Segments shorter than this will be discarded
// distance_threshold 1.41421356 - A point placed from a hypothesis line
// segment farther than this will be
// regarded as an outlier
// canny_th1 50 - First threshold for
// hysteresis procedure in Canny()
// canny_th2 50 - Second threshold for
// hysteresis procedure in Canny()
// canny_aperture_size 3 - Aperturesize for the sobel operator in Canny().
// If zero, Canny() is not applied and the input
// image is taken as an edge image.
// do_merge false - If true, incremental merging of segments
// will be performed
int length_threshold = 10;
float distance_threshold = 1.41421356f;
double canny_th1 = 50.0;
double canny_th2 = 50.0;
int canny_aperture_size = 3;
bool do_merge = false;
distance_threshold, canny_th1, canny_th2, canny_aperture_size,
do_merge);
vector<Vec4f> lines;
// Because of some CPU's power strategy, it seems that the first running of
// an algorithm takes much longer. So here we run the algorithm 10 times
// to see the algorithm's processing time with sufficiently warmed-up
// CPU performance.
for (int run_count = 0; run_count < 5; run_count++) {
double freq = getTickFrequency();
lines.clear();
int64 start = getTickCount();
// Detect the lines with FLD
fld->detect(image, lines);
double duration_ms = double(getTickCount() - start) * 1000 / freq;
cout << "Elapsed time for FLD " << duration_ms << " ms." << endl;
}
// Show found lines with FLD
Mat line_image_fld(image);
fld->drawSegments(line_image_fld, lines);
imshow("FLD result", line_image_fld);
waitKey(1);
vector<Vec6d> ellipses;
for (int run_count = 0; run_count < 5; run_count++) {
double freq = getTickFrequency();
lines.clear();
int64 start = getTickCount();
// Detect edges
//you should call this before detectLines() and detectEllipses()
ed->detectEdges(image);
// Detect lines
ed->detectLines(lines);
double duration_ms = double(getTickCount() - start) * 1000 / freq;
cout << "Elapsed time for EdgeDrawing detectLines " << duration_ms << " ms." << endl;
start = getTickCount();
// Detect circles and ellipses
ed->detectEllipses(ellipses);
duration_ms = double(getTickCount() - start) * 1000 / freq;
cout << "Elapsed time for EdgeDrawing detectEllipses " << duration_ms << " ms." << endl;
}
Mat edge_image_ed = Mat::zeros(image.size(), CV_8UC3);
vector<vector<Point> > segments = ed->getSegments();
for (size_t i = 0; i < segments.size(); i++)
{
const Point* pts = &segments[i][0];
int n = (int)segments[i].size();
polylines(edge_image_ed, &pts, &n, 1, false, Scalar((rand() & 255), (rand() & 255), (rand() & 255)), 1);
}
imshow("EdgeDrawing detected edges", edge_image_ed);
Mat line_image_ed(image);
fld->drawSegments(line_image_ed, lines);
// Draw circles and ellipses
for (size_t i = 0; i < ellipses.size(); i++)
{
Point center((int)ellipses[i][0], (int)ellipses[i][1]);
Size axes((int)ellipses[i][2] + (int)ellipses[i][3], (int)ellipses[i][2] + (int)ellipses[i][4]);
double angle(ellipses[i][5]);
Scalar color = ellipses[i][2] == 0 ? Scalar(255, 255, 0) : Scalar(0, 255, 0);
ellipse(line_image_ed, center, axes, angle, 0, 360, color, 2, LINE_AA);
}
imshow("EdgeDrawing result", line_image_ed);
return 0;
}

Constructor & Destructor Documentation

◆ ~FastLineDetector()

virtual cv::ximgproc::FastLineDetector::~FastLineDetector ( )
inlinevirtual

Member Function Documentation

◆ detect()

virtual void cv::ximgproc::FastLineDetector::detect ( InputArray  _image,
OutputArray  _lines 
)
pure virtual
Python:
_lines=cv.ximgproc_FastLineDetector.detect(_image[, _lines])

Finds lines in the input image. This is the output of the default parameters of the algorithm on the above shown image.

image
Parameters
_imageA grayscale (CV_8UC1) input image. If only a roi needs to be selected, use: fld_ptr-\>detect(image(roi), lines, ...); lines += Scalar(roi.x, roi.y, roi.x, roi.y);
_linesA vector of Vec4f elements specifying the beginning and ending point of a line. Where Vec4f is (x1, y1, x2, y2), point 1 is the start, point 2 - end. Returned lines are directed so that the brighter side is on their left.
Examples
fld_lines.cpp.

◆ drawSegments()

virtual void cv::ximgproc::FastLineDetector::drawSegments ( InputOutputArray  _image,
InputArray  lines,
bool  draw_arrow = false 
)
pure virtual
Python:
_image=cv.ximgproc_FastLineDetector.drawSegments(_image, lines[, draw_arrow])

Draws the line segments on a given image.

Parameters
_imageThe image, where the lines will be drawn. Should be bigger or equal to the image, where the lines were found.
linesA vector of the lines that needed to be drawn.
draw_arrowIf true, arrow heads will be drawn.
Examples
fld_lines.cpp.

The documentation for this class was generated from the following file:
cv::ximgproc::EdgeDrawing::SOBEL
@ SOBEL
Definition: edge_drawing.hpp:39
cv::Point_< int >
cv::samples::findFile
cv::String findFile(const cv::String &relative_path, bool required=true, bool silentMode=false)
Try to find requested data file.
cv::ximgproc::EdgeDrawing::detectLines
virtual void detectLines(OutputArray lines)=0
Detects lines.
cv::Mat::zeros
static MatExpr zeros(int rows, int cols, int type)
Returns a zero array of the specified size and type.
cv::ximgproc::EdgeDrawing::getSegments
virtual std::vector< std::vector< Point > > getSegments()=0
cv::ximgproc::EdgeDrawing::detectEdges
virtual void detectEdges(InputArray src)=0
Detects edges and prepares them to detect lines and ellipses.
cv::waitKey
int waitKey(int delay=0)
Waits for a pressed key.
cv::ximgproc::EdgeDrawing::detectEllipses
virtual void detectEllipses(OutputArray ellipses)=0
Detects circles and ellipses.
cv::Size_
Template class for specifying the size of an image or rectangle.
Definition: types.hpp:315
highgui.hpp
int64
int64_t int64
Definition: interface.h:61
cv::Scalar_< double >
cv::ximgproc::FastLineDetector::drawSegments
virtual void drawSegments(InputOutputArray _image, InputArray lines, bool draw_arrow=false)=0
Draws the line segments on a given image.
cv::ximgproc::EdgeDrawing::Params::AnchorThresholdValue
int AnchorThresholdValue
threshold value used to create gradient image.
Definition: edge_drawing.hpp:54
cv::ximgproc::FastLineDetector::detect
virtual void detect(InputArray _image, OutputArray _lines)=0
Finds lines in the input image. This is the output of the default parameters of the algorithm on the ...
cv::imread
Mat imread(const String &filename, int flags=IMREAD_COLOR)
Loads an image from a file.
cv::Mat::empty
bool empty() const
Returns true if the array has no elements.
ximgproc.hpp
cv::polylines
void polylines(InputOutputArray img, const Point *const *pts, const int *npts, int ncontours, bool isClosed, const Scalar &color, int thickness=1, int lineType=LINE_8, int shift=0)
CV_8UC3
#define CV_8UC3
Definition: interface.h:90
cv::Mat::size
MatSize size
Definition: mat.hpp:2118
imgcodecs.hpp
cv::IMREAD_GRAYSCALE
@ IMREAD_GRAYSCALE
If set, always convert image to the single channel grayscale image (codec internal conversion).
Definition: imgcodecs.hpp:71
cv::getTickCount
int64 getTickCount()
Returns the number of ticks.
cv::gapi::streaming::size
GOpaque< Size > size(const GMat &src)
Gets dimensions from Mat.
cv::Ptr
std::shared_ptr< _Tp > Ptr
Definition: cvstd_wrapper.hpp:23
cv::ximgproc::createFastLineDetector
Ptr< FastLineDetector > createFastLineDetector(int _length_threshold=10, float _distance_threshold=1.414213562f, double _canny_th1=50.0, double _canny_th2=50.0, int _canny_aperture_size=3, bool _do_merge=false)
Creates a smart pointer to a FastLineDetector object and initializes it.
cv::ximgproc::createEdgeDrawing
Ptr< EdgeDrawing > createEdgeDrawing()
Creates a smart pointer to a EdgeDrawing object and initializes it.
cv::imshow
void imshow(const String &winname, InputArray mat)
Displays an image in the specified window.
cv::ximgproc
Definition: brightedges.hpp:47
cv::getTickFrequency
double getTickFrequency()
Returns the number of ticks per second.
cv::Scalar
Scalar_< double > Scalar
Definition: types.hpp:669
cv::Mat
n-dimensional dense array class
Definition: mat.hpp:801
cv::ximgproc::EdgeDrawing::Params::EdgeDetectionOperator
int EdgeDetectionOperator
indicates the operator used for gradient calculation.The following operation flags are available(cv::...
Definition: edge_drawing.hpp:50
cv::CommandLineParser
Designed for command line parsing.
Definition: utility.hpp:799
cv
"black box" representation of the file storage associated with a file on disk.
Definition: affine.hpp:51
imgproc.hpp
cv::ximgproc::EdgeDrawing::Params::GradientThresholdValue
int GradientThresholdValue
threshold value used to create gradient image.
Definition: edge_drawing.hpp:52
cv::ellipse
void ellipse(InputOutputArray img, Point center, Size axes, double angle, double startAngle, double endAngle, const Scalar &color, int thickness=1, int lineType=LINE_8, int shift=0)
Draws a simple or thick elliptic arc or fills an ellipse sector.
cv::ximgproc::EdgeDrawing::params
Params params
Definition: edge_drawing.hpp:97
cv::LINE_AA
@ LINE_AA
antialiased line
Definition: imgproc.hpp:816