checkerboard_find_corners.cpp

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/* +------------------------------------------------------------------------+
   |                     Mobile Robot Programming Toolkit (MRPT)            |
   |                          https://www.mrpt.org/                         |
   |                                                                        |
   | Copyright (c) 2005-2020, Individual contributors, see AUTHORS file     |
   | See: https://www.mrpt.org/Authors - All rights reserved.               |
   | Released under BSD License. See: https://www.mrpt.org/License          |
   +------------------------------------------------------------------------+ */

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

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

// Universal include for all versions of OpenCV
#include <mrpt/3rdparty/do_opencv_includes.h>
#include "checkerboard_ocamcalib_detector.h"

using namespace mrpt;
using namespace mrpt::vision;
using namespace mrpt::img;
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::img::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;

    cv::Mat cvImg = img.asCvMat<cv::Mat>(SHALLOW_COPY);
    if (!useScaramuzzaMethod)
    {
        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)
    {
        IplImage iplImg = cvIplImage(cvImg);
        // Refine corners:
        cvFindCornerSubPix(
            &iplImg, &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.emplace_back(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::img::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);
    const cv::Mat img_m = img.asCvMat<cv::Mat>(SHALLOW_COPY);
    const IplImage img_ipl = cvIplImage(img_m);

    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_ipl, &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].x,
                                            cornerCoords[i][0].y},
                pt_x1{cornerCoords[i][1].x, cornerCoords[i][1].y},
                pt_y1{cornerCoords[i][check_size_x].x,
                      cornerCoords[i][check_size_x].y};
            const mrpt::math::TPoint3D Ax = pt_x1 - pt_0;  // z=0
            const mrpt::math::TPoint3D Ay = pt_y1 - pt_0;  // z=0

            const auto 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
}