Write PGM function overwritting existing file.

Question

Im having problems understanding how to write a PGM file using data. This function i have overwrites the existing txt document instead of creating a PGM file. Im unsure whether my issue is lies within my Read_text function or somewhere else. Can anyone help me understand this issue and fix it please?

double* read_text(char *fileName, int sizeR, int sizeC)
{
    double* data = new double[sizeR*sizeC];
    int i = 0;
    std::ifstream myfile(fileName);
    if (myfile.is_open())
    {
        while (myfile.good())
        {
            if (i>sizeR*sizeC - 1) break;
            myfile >> *(data + i);
            std::cout << *(data+i) << ' '; //This line display the converted data on the screen, you may comment it out. 
            i++;
        }
        myfile.close();
    }
    else std::cout << "Unable to open file";
    std::cout << i;
    return data;
}

void write_pgm(char *filename, double *data, int sizeR, int sizeC, int Q)
{
    int i, j;
    unsigned char *image;
    std::ofstream myfile;

    image = (unsigned char *) new unsigned char[sizeR*sizeC];

    // convert the integer values to unsigned char

    for (i = 0; i<sizeR*sizeC; i++)
        image[i] = (unsigned char)data[i];

    myfile.open(filename, std::ios::out | std::ios::binary | std::ios::trunc);

    if (!myfile) {
        std::cout << "Can't open file: " << filename << std::endl;
        exit(1);
    }

    myfile << "P5" << std::endl;
    myfile << sizeC << " " << sizeR << std::endl;
    myfile << Q << std::endl;

    myfile.write(reinterpret_cast<char *>(image), (sizeR*sizeC)*sizeof(unsigned char));

    if (myfile.fail()) {
        std::cout << "Can't write image " << filename << std::endl;
        exit(0);
    }

    myfile.close();
    std::cout << "Finsihed " << std::endl;
    delete[] image;

}    
void main() {
    double* data = read_text("Wally_grey.txt", rows(), columns());
    std::cout << data << std::endl;
    write_pgm("Wally_grey.txt",data, rows(), columns(), 255);
    getchar();
}