Read - write file.txt in C++

We have the located file with name:   c:/input_data/matrix.txt, data1.txt, data2.txt….

Ex:

matrix.txt:        m00 m01 m02

                        m10 m11 m12

                        m20 m21 m22

C++:

Read 1 file matrix.txt:

CMatrix intrinsic_matrix(4);                                           //create matrix 4x4

string datain_file = “c:/input_data/ matrix.txt”;                  //direction of file

string sline;

istringstream ssline;

ifstream matrix_file;

matrix_file.open(datain_file);

if (!matrix_file.data()){

            cout << " matrix_file was not found!" << endl;

            exit(0);

}

for (auto i(0); i < 3; i++){

            getline(matrix_file, sline);

            ssline.str(sline);                                                      //Convert to stream

            ssline >> intrinsic_matrix(i, 0) >> intrinsic_matrix(i, 1) >> intrinsic_matrix(i, 2);

            ssline.clear();

}

matrix_file.close();

//-----------------------------------------------------------------------------------------------

data1.txt:          r00 r01 r02 t0,  data2.txt …        //include Rotation matrix and translation vector

                        r10 r11 r12 t1

                        r20 r21 r22 t2

Read all file data1.txt … datak.txt:             // k file data.txt

CMatrix extrinsic_matrix(4);                            //create matrix 4x4

CMatrix Rotation(3);                                        //Rotation matrix

CMatrix Rotation_Transpose(3);                      //Transposed matrix of the rotation matrix

CVector Translation(3);                                    //Translation vector

ostringstream RT_file;    

string sline;

istringstream ssline;

ifstream datafile;

for (auto i(0); i < k; i++){

      RT_file << “c:/input_data/ data”<< k << “txt”;     //direction of file

datafile.open(RT_file.str());

if (!RT_file.str().data()){

       cout << " RT_file was not found!" << endl;

       exit(0);

}

for (auto i(0); i < 3; i++){

       getline(datafile, sline);

       ssline.str(sline);                                                      //Convert to stream

       ssline >> extrinsic_matrix(i,0) >> extrinsic_matrix(i,1) >> extrinsic_matrix(i,2);

       ssline.clear();

}

datafile.close();

 //It is necessary in order to homogeneous coordinates

intrinsic_matrix(3, 3) = 1.0; //fourth column,fourth row :1

extrinsic_matrix(3, 3) = 1.0; //fourth column,fourth row :1

for (int x(0); x<3; x++){

       Translation[x] = extrinsic_matrix(x, 3);                        //only 3rd column

       for (int y(0); y<3; y++){

                   Rotation(x, y) = extrinsic_matrix(x, y);

       }

}

//To return the initial state

RT_file.str(empty_string);

RT_file.clear();

}

Write to file .txt

CVector3d* Up_Camera;   //output

string camerafile = "D://output_file/Up_Camera_Position.txt";

ofstream outfile(camerafile);

for (auto i(0); i < k; i++){

                                                     //calculate the Up_Camera.x,y,z and then save:

….

outfile << Up_Camera[k].x << " " << Up_Camera[k].y << " " << Up_Camera[k].z << endl;

}