checkerboard_find_corners.cpp

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/* +---------------------------------------------------------------------------+
   |                     Mobile Robot Programming Toolkit (MRPT)               |
   |                          http://www.mrpt.org/                             |
   |                                                                           |
   | Copyright (c) 2005-2017, Individual contributors, see AUTHORS file        |
   | See: http://www.mrpt.org/Authors - All rights reserved.                   |
   | Released under BSD License. See details in http://www.mrpt.org/License    |
   +---------------------------------------------------------------------------+ */

#include "vision-precomp.h"   // Precompiled headers

#include <mrpt/vision/chessboard_find_corners.h>
#include <mrpt/math/geometry.h> // crossProduct3D()

// Universal include for all versions of OpenCV
#include <mrpt/otherlibs/do_opencv_includes.h> 
#include "checkerboard_ocamcalib_detector.h"

using namespace mrpt;
using namespace mrpt::vision;
using namespace mrpt::utils;
using namespace mrpt::math;
using namespace std;


/** Look for the corners of a chessboard in the image
  * \param cornerCoords [OUT] The pixel coordinates of all the corners.
  * \param check_size_x [IN] The number of squares, in the X direction
  * \param check_size_y [IN] The number of squares, in the Y direction
  * \param normalize_image [IN] Whether to normalize the image before detection
  * \param useScaramuzzaMethod [IN] Whether to use the alternative, more robust method by M. Rufli, D. Scaramuzza, and R. Siegwart.
  *
  * \return true on success
  */
bool mrpt::vision::findChessboardCorners(
        const mrpt::utils::CImage &in_img,
        std::vector<TPixelCoordf>       &cornerCoords,
        unsigned int  check_size_x,
        unsigned int  check_size_y,
        bool            normalize_image,
        bool            useScaramuzzaMethod)
{
#if MRPT_HAS_OPENCV
        MRPT_START

        ASSERT_(check_size_y>0 && check_size_x>0)

        // Grayscale version:
        const CImage img( in_img, FAST_REF_OR_CONVERT_TO_GRAY );

        // Try with expanded versions of the image if it fails to detect the checkerboard:
        int corners_count;
        bool corners_found=false;

        const CvSize check_size = cvSize(check_size_x, check_size_y);

        const int CORNERS_COUNT = check_size_x * check_size_y;

        vector<CvPoint2D32f> corners_list;
        corners_count = CORNERS_COUNT;
        corners_list.resize( CORNERS_COUNT );

        cornerCoords.clear();

        int find_chess_flags = cv::CALIB_CB_ADAPTIVE_THRESH;
        if (normalize_image)
                find_chess_flags |= cv::CALIB_CB_NORMALIZE_IMAGE;

        if (!useScaramuzzaMethod)
        {
                cv::Mat cvImg = cv::cvarrToMat(img.getAs<IplImage>());
                
                vector<cv::Point2f> pointbuf;

                // Standard OpenCV's function:
                corners_found = 0 != cv::findChessboardCorners(
                        cvImg,
                        check_size,
                        pointbuf,
                        find_chess_flags);

                corners_list.resize(pointbuf.size());
                for (size_t i=0;i<pointbuf.size();i++) {
                        corners_list[i].x = pointbuf[i].x;
                        corners_list[i].y = pointbuf[i].y;
                }
        }
        else
        {
                // Return: -1: errors, 0: not found, 1: found OK
                corners_found = 1 == cvFindChessboardCorners3(
                        img,
                        check_size,
                        corners_list
                        );
        }

        // Check # of corners:
        if (corners_found && corners_count!=CORNERS_COUNT)
                corners_found=false;

        if( corners_found )
        {
                // Refine corners:
                cvFindCornerSubPix(
                        img.getAs<IplImage>(),
                        &corners_list[0],
                        corners_count,
                        cvSize(5,5),    // window
                        cvSize(-1,-1),
                        cvTermCriteria( CV_TERMCRIT_ITER|CV_TERMCRIT_EPS, 10, 0.01f ));

                // save the corners in the data structure:
                int y;
                unsigned int k;
                for( y = 0, k = 0; y < check_size.height; y++ )
                        for( int x = 0; x < check_size.width; x++, k++ )
                                cornerCoords.push_back(  TPixelCoordf( corners_list[k].x, corners_list[k].y ) );
        }


        return corners_found;

        MRPT_END
#else
        return false;
#endif
}


/** Look for the corners of one or more chessboard/checkerboards in the image.
  *  This method uses an improved version of OpenCV's cvFindChessboardCorners published
  *   by M. Rufli, D. Scaramuzza, and R. Siegwart.
  *  That method has been extended in this MRPT implementation to automatically detect a
  *   number of different checkerboards in the same image.
  *
  * \param cornerCoords [OUT] A vector of N vectors of pixel coordinates, for each of the N chessboards detected.
  * \param check_size_x [IN] The number of squares, in the X direction
  * \param check_size_y [IN] The number of squares, in the Y direction
  *
  *
  * \sa mrpt::vision::checkerBoardCameraCalibration, drawChessboardCorners
  */
void mrpt::vision::findMultipleChessboardsCorners(
        const mrpt::utils::CImage &in_img,
        std::vector<std::vector<TPixelCoordf> >         &cornerCoords,
        unsigned int  check_size_x,
        unsigned int  check_size_y )
{
#if MRPT_HAS_OPENCV
        // Grayscale version:
        const CImage img( in_img, FAST_REF_OR_CONVERT_TO_GRAY );

        std::vector<std::vector<CvPoint2D32f> >  corners_list;

        // Return: -1: errors, 0: not found, 1: found OK
        bool corners_found = find_chessboard_corners_multiple(
                img,
                cvSize(check_size_x,check_size_y),
                corners_list);

        if( corners_found && !corners_list.empty() )
        {
                // Alloc space for output points:
                cornerCoords.resize( corners_list.size() );

                // Refine corners:
                for (size_t i=0;i<corners_list.size();i++)
                {
                        ASSERT_(corners_list[i].size()==check_size_x*check_size_y)

                        cvFindCornerSubPix(
                                img.getAs<IplImage>(),
                                &corners_list[i][0],
                                check_size_x*check_size_y,
                                cvSize(5,5),    // window
                                cvSize(-1,-1),
                                cvTermCriteria( CV_TERMCRIT_ITER|CV_TERMCRIT_EPS, 10, 0.01f ));

                        // save the corners in the data structure:
                        for( unsigned int y = 0, k = 0; y < check_size_y; y++ )
                                for( unsigned int x = 0; x < check_size_x; x++, k++ )
                                        cornerCoords[i].push_back(  TPixelCoordf( corners_list[i][k].x, corners_list[i][k].y ) );


                        // Consistency of the counter-clockwise XYZ reference system and corners ORDER.

                        // Key idea: The cross product of X * Y must point outwards the screen:

                        const mrpt::math::TPoint2D
                                pt_0  = cornerCoords[i][0],
                                pt_x1 = cornerCoords[i][1],
                                pt_y1 = cornerCoords[i][check_size_x];
                        const mrpt::math::TPoint3D Ax = pt_x1 - pt_0;  // z=0
                        const mrpt::math::TPoint3D Ay = pt_y1 - pt_0;  // z=0

                        const Eigen::Matrix<double,3,1> Az = mrpt::math::crossProduct3D(Ax,Ay);
                        if (Az[2] > 0) {
                                // Invert all rows (X):
                                for( unsigned int y = 0; y < check_size_y; y++ )
                                        std::reverse( cornerCoords[i].begin()+y*check_size_x, cornerCoords[i].begin()+(y+1)*check_size_x );
                        }
                }
        }
        else
        {       // Not found.
                cornerCoords.clear();
                return;
        }

#endif
}