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example_18-01_from_disk.cpp
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example_18-01_from_disk.cpp
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// Example 18-1. Reading a chessboard’s width and height, reading them from disk and calibrating
// the requested number of views, and calibrating the camera
// You need these includes for the function
// #include <windows.h> // for windows systems
#include <dirent.h> // for linux systems
#include <sys/stat.h> // for linux systems
#include <iostream> // cout
#include <algorithm> // std::sort
#include <opencv2/opencv.hpp>
using std::string;
using std::vector;
using std::cout;
using std::cerr;
using std::endl;
// Returns a list of files in a directory (except the ones that begin with a dot)
int readFilenames(vector<string>& filenames, const string& directory) {
#ifdef WINDOWS
HANDLE dir;
WIN32_FIND_DATA file_data;
if ((dir = FindFirstFile((directory + "/*").c_str(), &file_data)) == INVALID_HANDLE_VALUE)
return; // no files found
do {
const string file_name = file_data.cFileName;
const string full_file_name = directory + "/" + file_name;
const bool is_directory = (file_data.dwFileAttributes & FILE_ATTRIBUTE_DIRECTORY) != 0;
if (file_name[0] == '.')
continue;
if (is_directory)
continue;
filenames.push_back(full_file_name);
} while (FindNextFile(dir, &file_data));
FindClose(dir);
#else
DIR *dir;
class dirent *ent;
class stat st;
dir = opendir(directory.c_str());
while ((ent = readdir(dir)) != NULL) {
const string file_name = ent->d_name;
const string full_file_name = directory + "/" + file_name;
if (file_name[0] == '.')
continue;
if (stat(full_file_name.c_str(), &st) == -1)
continue;
const bool is_directory = (st.st_mode & S_IFDIR) != 0;
if (is_directory)
continue;
// filenames.push_back(full_file_name); // returns full path
filenames.push_back(file_name); // returns just filename
}
closedir(dir);
#endif
std::sort(filenames.begin(), filenames.end()); // optional, sort the filenames
return(filenames.size()); // return how many we found
} // GetFilesInDirectory
void help(const char **argv) {
cout << "\n\n"
<< "Example 18-1 (from disk):\Enter a chessboard’s width and height,\n"
<< " reading in a directory of chessboard images,\n"
<< " and calibrating the camera\n\n"
<< "Call:\n" << argv[0] << " <1board_width> <2board_height> <3number_of_boards>"
<< " <4ms_delay_framee_capture> <5image_scaling_factor> <6path_to_calibration_images>\n\n"
<< "\nExample:\n"
<< "./example_18-01_from_disk 9 6 14 100 1.0 ../stereoData/\nor:\n"
<< "./example_18-01_from_disk 12 12 28 100 0.5 ../calibration/\n\n"
<< " * First it reads in checker boards and calibrates itself\n"
<< " * Then it saves and reloads the calibration matricies\n"
<< " * Then it creates an undistortion map and finaly\n"
<< " * It displays an undistorted image\n"
<< endl;
}
int main(int argc, const char *argv[]) {
float image_sf = 0.5f; // image scaling factor
int delay = 250; // miliseconds
int board_w = 0;
int board_h = 0;
if (argc != 7) {
cout << "\nERROR: Wrong number (" << argc - 1
<< ") of arguments, should be (6) input parameters\n";
help(argv);
return -1;
}
board_w = atoi(argv[1]);
board_h = atoi(argv[2]);
int n_boards = atoi(argv[3]); // how many boards max to read
delay = atof(argv[4]); // milisecond delay
image_sf = atof(argv[5]);
int board_n = board_w * board_h; // number of corners
cv::Size board_sz = cv::Size(board_w, board_h); // width and height of the board
string folder = argv[6];
cout << "Reading in directory " << folder << endl;
vector<string> filenames;
int num_files = readFilenames(filenames, folder);
cout << " ... Done. Number of files = " << num_files << "\n" << endl;
// PROVIDE PPOINT STORAGE
//
vector<vector<cv::Point2f> > image_points;
vector<vector<cv::Point3f> > object_points;
/////////// COLLECT //////////////////////////////////////////////
// Capture corner views: loop through all calibration images
// collecting all corners on the boards that are found
//
cv::Size image_size;
int board_count = 0;
for (size_t i = 0; (i < filenames.size()) && (board_count < n_boards); ++i) {
cv::Mat image, image0 = cv::imread(folder + filenames[i]);
board_count += 1;
if (!image0.data) { // protect against no file
cerr << folder + filenames[i] << ", file #" << i << ", is not an image" << endl;
continue;
}
image_size = image0.size();
cv::resize(image0, image, cv::Size(), image_sf, image_sf, cv::INTER_LINEAR);
// Find the board
//
vector<cv::Point2f> corners;
bool found = cv::findChessboardCorners(image, board_sz, corners);
// Draw it
//
drawChessboardCorners(image, board_sz, corners, found); // will draw only if found
// If we got a good board, add it to our data
//
if (found) {
image ^= cv::Scalar::all(255);
cv::Mat mcorners(corners);
// do not copy the data
mcorners *= (1.0 / image_sf);
// scale the corner coordinates
image_points.push_back(corners);
object_points.push_back(vector<cv::Point3f>());
vector<cv::Point3f> &opts = object_points.back();
opts.resize(board_n);
for (int j = 0; j < board_n; j++) {
opts[j] = cv::Point3f(static_cast<float>(j / board_w),
static_cast<float>(j % board_w), 0.0f);
}
cout << "Collected " << static_cast<int>(image_points.size())
<< "total boards. This one from chessboard image #"
<< i << ", " << folder + filenames[i] << endl;
}
cv::imshow("Calibration", image);
// show in color if we did collect the image
if ((cv::waitKey(delay) & 255) == 27) {
return -1;
}
}
// END COLLECTION WHILE LOOP.
cv::destroyWindow("Calibration");
cout << "\n\n*** CALIBRATING THE CAMERA...\n" << endl;
/////////// CALIBRATE //////////////////////////////////////////////
// CALIBRATE THE CAMERA!
//
cv::Mat intrinsic_matrix, distortion_coeffs;
double err = cv::calibrateCamera(
object_points, image_points, image_size, intrinsic_matrix,
distortion_coeffs, cv::noArray(), cv::noArray(),
cv::CALIB_ZERO_TANGENT_DIST | cv::CALIB_FIX_PRINCIPAL_POINT);
// SAVE THE INTRINSICS AND DISTORTIONS
cout << " *** DONE!\n\nReprojection error is " << err
<< "\nStoring Intrinsics.xml and Distortions.xml files\n\n";
cv::FileStorage fs("intrinsics.xml", cv::FileStorage::WRITE);
fs << "image_width" << image_size.width << "image_height" << image_size.height
<< "camera_matrix" << intrinsic_matrix << "distortion_coefficients"
<< distortion_coeffs;
fs.release();
// EXAMPLE OF LOADING THESE MATRICES BACK IN:
fs.open("intrinsics.xml", cv::FileStorage::READ);
cout << "\nimage width: " << static_cast<int>(fs["image_width"]);
cout << "\nimage height: " << static_cast<int>(fs["image_height"]);
cv::Mat intrinsic_matrix_loaded, distortion_coeffs_loaded;
fs["camera_matrix"] >> intrinsic_matrix_loaded;
fs["distortion_coefficients"] >> distortion_coeffs_loaded;
cout << "\nintrinsic matrix:" << intrinsic_matrix_loaded;
cout << "\ndistortion coefficients: " << distortion_coeffs_loaded << "\n" << endl;
// Build the undistort map which we will use for all
// subsequent frames.
//
cv::Mat map1, map2;
cv::initUndistortRectifyMap(intrinsic_matrix_loaded, distortion_coeffs_loaded,
cv::Mat(), intrinsic_matrix_loaded, image_size,
CV_16SC2, map1, map2);
////////// DISPLAY //////////////////////////////////////////////
cout << "*****************\nPRESS A KEY TO SEE THE NEXT IMAGE, ESQ TO QUIT\n"
<< "****************\n" << endl;
board_count = 0; // resent max boards to read
for (size_t i = 0; (i < filenames.size()) && (board_count < n_boards); ++i) {
cv::Mat image, image0 = cv::imread(folder + filenames[i]);
++board_count;
if (!image0.data) { // protect against no file
cerr << folder + filenames[i] << ", file #" << i << ", is not an image" << endl;
continue;
}
// Just run the camera to the screen, now showing the raw and
// the undistorted image.
//
cv::remap(image0, image, map1, map2, cv::INTER_LINEAR,
cv::BORDER_CONSTANT, cv::Scalar());
cv::imshow("Original", image0);
cv::imshow("Undistorted", image);
if ((cv::waitKey(0) & 255) == 27) {
break;
}
}
return 0;
}