OpenCV  4.5.4-dev
Open Source Computer Vision
Public Member Functions | List of all members
cv::LineSegmentDetector Class Referenceabstract

Line segment detector class. More...

#include <opencv2/imgproc.hpp>

Inheritance diagram for cv::LineSegmentDetector:
cv::Algorithm

Public Member Functions

virtual ~LineSegmentDetector ()
 
virtual int compareSegments (const Size &size, InputArray lines1, InputArray lines2, InputOutputArray image=noArray())=0
 Draws two groups of lines in blue and red, counting the non overlapping (mismatching) pixels. More...
 
virtual void detect (InputArray image, OutputArray lines, OutputArray width=noArray(), OutputArray prec=noArray(), OutputArray nfa=noArray())=0
 Finds lines in the input image. More...
 
virtual void drawSegments (InputOutputArray image, InputArray lines)=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
 
virtual void write (FileStorage &fs) const
 Stores algorithm parameters in a file storage. More...
 
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...
 

Additional Inherited Members

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

Detailed Description

Line segment detector class.

following the algorithm described at [265] .

Note
Implementation has been removed from OpenCV version 3.4.6 to 3.4.15 and version 4.1.0 to 4.5.3 due original code license conflict. restored again after Computation of a NFA code published under the MIT license.

Constructor & Destructor Documentation

◆ ~LineSegmentDetector()

virtual cv::LineSegmentDetector::~LineSegmentDetector ( )
inlinevirtual

Member Function Documentation

◆ compareSegments()

virtual int cv::LineSegmentDetector::compareSegments ( const Size size,
InputArray  lines1,
InputArray  lines2,
InputOutputArray  image = noArray() 
)
pure virtual
Python:
cv.LineSegmentDetector.compareSegments(size, lines1, lines2[, image]) -> retval, image

Draws two groups of lines in blue and red, counting the non overlapping (mismatching) pixels.

Parameters
sizeThe size of the image, where lines1 and lines2 were found.
lines1The first group of lines that needs to be drawn. It is visualized in blue color.
lines2The second group of lines. They visualized in red color.
imageOptional image, where the lines will be drawn. The image should be color(3-channel) in order for lines1 and lines2 to be drawn in the above mentioned colors.

◆ detect()

virtual void cv::LineSegmentDetector::detect ( InputArray  image,
OutputArray  lines,
OutputArray  width = noArray(),
OutputArray  prec = noArray(),
OutputArray  nfa = noArray() 
)
pure virtual
Python:
cv.LineSegmentDetector.detect(image[, lines[, width[, prec[, nfa]]]]) -> lines, width, prec, nfa

Finds lines in the input image.

This is the output of the default parameters of the algorithm on the above shown image.

building_lsd.png
image
Parameters
imageA grayscale (CV_8UC1) input image. If only a roi needs to be selected, use: lsd_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 strictly oriented depending on the gradient.
widthVector of widths of the regions, where the lines are found. E.g. Width of line.
precVector of precisions with which the lines are found.
nfaVector containing number of false alarms in the line region, with precision of 10%. The bigger the value, logarithmically better the detection.
  • -1 corresponds to 10 mean false alarms
  • 0 corresponds to 1 mean false alarm
  • 1 corresponds to 0.1 mean false alarms This vector will be calculated only when the objects type is LSD_REFINE_ADV.

◆ drawSegments()

virtual void cv::LineSegmentDetector::drawSegments ( InputOutputArray  image,
InputArray  lines 
)
pure virtual
Python:
cv.LineSegmentDetector.drawSegments(image, lines) -> image

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.

The documentation for this class was generated from the following file: