vpDetectorQRCode Class Reference

#include <vpDetectorQRCode.h>

Inheritance diagram for vpDetectorQRCode:

Public Member Functions
	vpDetectorQRCode ()
bool	detect (const vpImage< unsigned char > &I) VP_OVERRIDE

Protected Attributes
zbar::ImageScanner	m_scanner

Inherited functionalities from vpDetectorBase
std::vector< std::vector< vpImagePoint > >	m_polygon
std::vector< std::string >	m_message
size_t	m_nb_objects
unsigned long	m_timeout_ms
vpRect	getBBox (size_t i) const
vpImagePoint	getCog (size_t i) const
std::vector< std::string > &	getMessage ()
std::string &	getMessage (size_t i)
size_t	getNbObjects () const
std::vector< std::vector< vpImagePoint > > &	getPolygon ()
std::vector< vpImagePoint > &	getPolygon (size_t i)
void	setTimeout (unsigned long timeout_ms)

Detailed Description

Base class for bar code detector. This class is a wrapper over libzbar available from http://zbar.sourceforge.net. Installation instructions are provided here https://visp.inria.fr/3rd_zbar.

The detect() function allows to detect multiple QR codes in an image. Once detected, for each QR code it is possible to retrieve the location of the corners using getPolygon(), the encoded message using getMessage(), the bounding box using getBBox() and the center of gravity using getCog().

The following sample code shows how to use this class to detect QR codes in an image.

#include <visp3/detection/vpDetectorQRCode.h>
#include <visp3/io/vpImageIo.h>
 
#ifdef ENABLE_VISP_NAMESPACE
using namespace VISP_NAMESPACE_NAME;
#endif
 
int main()
{
#ifdef VISP_HAVE_ZBAR
  vpImage<unsigned char> I;
  vpImageIo::read(I, "bar-code.jpg");
 
  vpDetectorQRCode detector;
 
  bool status = detector.detect(I);
  if (status) {
    for(size_t i=0; i < detector.getNbObjects(); i++) {
      std::cout << "Bar code " << i << ":" << std::endl;
      std::vector<vpImagePoint> p = detector.getPolygon(i);
      for(size_t j=0; j < p.size(); j++)
        std::cout << "  Point " << j << ": " << p[j] << std::endl;
      std::cout << "  Message: \"" << detector.getMessage(i) << "\"" << std::endl;
    }
  }
#endif
}

The previous example may produce results like:

Bar code 0:
  Point 0: 48, 212
  Point 1: 57, 84
  Point 2: 188, 92
  Point 3: 183, 220
  Message: "qrcode 2"
Bar code 1:
  Point 0: 26, 550
  Point 1: 35, 409
  Point 2: 174, 414
  Point 3: 167, 555
  Message: "qrcode 1"

Tutorials & Examples

Tutorials
If you are interested in QR code detection, you may have a look at:

• Tutorial: Bar code detection
• Tutorial: Pose estimation from QRcode

Examples

tutorial-barcode-detector-live.cpp, tutorial-barcode-detector.cpp, and tutorial-pose-from-qrcode-image.cpp.

Definition at line 119 of file vpDetectorQRCode.h.

Constructor & Destructor Documentation

vpDetectorQRCode()

BEGIN_VISP_NAMESPACE vpDetectorQRCode::vpDetectorQRCode

(

)

Default constructor.

Definition at line 44 of file vpDetectorQRCode.cpp.

References m_scanner.

Member Function Documentation

detect()

bool vpDetectorQRCode::detect ( const vpImage< unsigned char > & I )

virtual

Detect QR codes in the image. Return true if a code is detected, false otherwise.

Parameters

I	: Input image.

Implements vpDetectorBase.

Examples

tutorial-pose-from-qrcode-image.cpp.

Definition at line 56 of file vpDetectorQRCode.cpp.

References vpDetectorBase::m_message, vpDetectorBase::m_nb_objects, vpDetectorBase::m_polygon, and m_scanner.

Referenced by visp.python.rbt.xfeat.XFeatTrackingBackend.XFeatTrackingBackend::process_frame().

getBBox()

vpRect vpDetectorBase::getBBox ( size_t i ) const

inherited

Return the bounding box of the ith object.

Examples

tutorial-barcode-detector-live.cpp, tutorial-barcode-detector.cpp, tutorial-face-detector-live-threaded.cpp, tutorial-face-detector-live.cpp, and tutorial-face-detector.cpp.

Definition at line 92 of file vpDetectorBase.cpp.

References m_polygon.

Referenced by detect().

getCog()

vpImagePoint vpDetectorBase::getCog ( size_t i ) const

inherited

Return the center of gravity location of the ith object.

Examples

servoBiclopsPoint2DArtVelocity.cpp, servoPololuPtuPoint2DJointVelocity.cpp, and tutorial-flir-ptu-ibvs.cpp.

Definition at line 78 of file vpDetectorBase.cpp.

References m_polygon.

Referenced by detect().

getMessage() [1/2]

std::vector< std::string > & vpDetectorBase::getMessage ( )

inlineinherited

Returns the contained message of the ith object if there is one.

Examples

catchAprilTag.cpp, catchArUco.cpp, tutorial-barcode-detector-live.cpp, tutorial-barcode-detector.cpp, tutorial-face-detector-live.cpp, and tutorial-face-detector.cpp.

Definition at line 98 of file vpDetectorBase.h.

References m_message.

getMessage() [2/2]

std::string & vpDetectorBase::getMessage ( size_t i )

inherited

Returns the contained message of the ith object if there is one.

Definition at line 64 of file vpDetectorBase.cpp.

References vpException::badValue, m_message, and m_polygon.

getNbObjects()

size_t vpDetectorBase::getNbObjects ( ) const

inlineinherited

Return the number of objects that are detected.

Examples

catchAprilTag.cpp, catchArUco.cpp, tutorial-barcode-detector-live.cpp, tutorial-barcode-detector.cpp, tutorial-face-detector-live.cpp, tutorial-face-detector.cpp, tutorial-flir-ptu-ibvs.cpp, tutorial-mb-generic-tracker-apriltag-rs2.cpp, tutorial-mb-generic-tracker-apriltag-webcam.cpp, and tutorial-pose-from-qrcode-image.cpp.

Definition at line 108 of file vpDetectorBase.h.

References m_nb_objects.

getPolygon() [1/2]

std::vector< std::vector< vpImagePoint > > & vpDetectorBase::getPolygon ( )

inlineinherited

Returns object container box as a vector of points.

Examples

catchAprilTag.cpp, tutorial-barcode-detector-live.cpp, tutorial-barcode-detector.cpp, and tutorial-pose-from-qrcode-image.cpp.

Definition at line 113 of file vpDetectorBase.h.

References m_polygon.

getPolygon() [2/2]

std::vector< vpImagePoint > & vpDetectorBase::getPolygon ( size_t i )

inherited

Returns ith object container box as a vector of points.

Definition at line 50 of file vpDetectorBase.cpp.

References vpException::badValue, and m_polygon.

setTimeout()

void vpDetectorBase::setTimeout ( unsigned long timeout_ms )

inlineinherited

Set detector timeout in milli-seconds. When set to 0, there is no timeout.

Definition at line 123 of file vpDetectorBase.h.

References m_timeout_ms.

Referenced by vpDetectorDataMatrixCode::vpDetectorDataMatrixCode().

Member Data Documentation

m_message

std::vector<std::string> vpDetectorBase::m_message

protectedinherited

Message attached to each object.

Definition at line 129 of file vpDetectorBase.h.

Referenced by vpDetectorAprilTag::detect(), vpDetectorAprilTag::detect(), vpDetectorDataMatrixCode::detect(), vpDetectorFace::detect(), vpDetectorQRCode::detect(), getMessage(), getMessage(), vpDetectorBase(), and vpDetectorBase().

m_nb_objects

size_t vpDetectorBase::m_nb_objects

protectedinherited

Number of detected objects.

Definition at line 130 of file vpDetectorBase.h.

Referenced by vpDetectorAprilTag::detect(), vpDetectorAprilTag::detect(), vpDetectorDataMatrixCode::detect(), vpDetectorFace::detect(), vpDetectorQRCode::detect(), getNbObjects(), vpDetectorBase(), and vpDetectorBase().

m_polygon

std::vector<std::vector<vpImagePoint> > vpDetectorBase::m_polygon

protectedinherited

For each object, defines the polygon that contains the object.

Definition at line 128 of file vpDetectorBase.h.

Referenced by vpDetectorAprilTag::detect(), vpDetectorAprilTag::detect(), vpDetectorDataMatrixCode::detect(), vpDetectorFace::detect(), vpDetectorQRCode::detect(), getBBox(), getCog(), getMessage(), getPolygon(), getPolygon(), vpDetectorAprilTag::getTagsCorners(), vpDetectorBase(), and vpDetectorBase().

m_scanner

zbar::ImageScanner vpDetectorQRCode::m_scanner

protected

QR code detector.

Definition at line 122 of file vpDetectorQRCode.h.

Referenced by detect(), and vpDetectorQRCode().

m_timeout_ms

unsigned long vpDetectorBase::m_timeout_ms

protectedinherited

Detection timeout.

Definition at line 131 of file vpDetectorBase.h.

Referenced by vpDetectorDataMatrixCode::detect(), setTimeout(), vpDetectorBase(), and vpDetectorBase().