mnist.cpp

#include "mnist.h"

//バイト列からintへの変換
int reverseInt(int i) {
    unsigned char c1, c2, c3, c4;

    c1 = i & 255;
    c2 = (i >> 8) & 255;
    c3 = (i >> 16) & 255;
    c4 = (i >> 24) & 255;

    return ((int) c1 << 24) + ((int) c2 << 16) + ((int) c3 << 8) + c4;
}

vector<vector<float> > Mnist::readTrainingFile(string filename) {
    ifstream ifs(filename.c_str(), std::ios::in | std::ios::binary);
    int magic_number = 0;
    int number_of_images = 0;
    int rows = 0;
    int cols = 0;

    //ヘッダー部より情報を読取る。
    ifs.read((char*) &magic_number, sizeof(magic_number));
    magic_number = reverseInt(magic_number);
    ifs.read((char*) &number_of_images, sizeof(number_of_images));
    number_of_images = reverseInt(number_of_images);
    ifs.read((char*) &rows, sizeof(rows));
    rows = reverseInt(rows);
    ifs.read((char*) &cols, sizeof(cols));
    cols = reverseInt(cols);

    vector<vector<float> > images(number_of_images);
    cout << magic_number << " " << number_of_images << " " << rows << " "
            << cols << endl;

    for (int i = 0; i < number_of_images; i++) {
        images[i].resize(rows * cols);

        for (int row = 0; row < rows; row++) {
            for (int col = 0; col < cols; col++) {
                unsigned char temp = 0;
                ifs.read((char*) &temp, sizeof(temp));
                images[i][rows * row + col] = (float) temp;
            }
        }
    }
    return images;
}

vector<float> Mnist::readLabelFile(string filename) {
    ifstream ifs(filename.c_str(), std::ios::in | std::ios::binary);
    int magic_number = 0;
    int number_of_images = 0;

    //ヘッダー部より情報を読取る。
    ifs.read((char*) &magic_number, sizeof(magic_number));
    magic_number = reverseInt(magic_number);
    ifs.read((char*) &number_of_images, sizeof(number_of_images));
    number_of_images = reverseInt(number_of_images);

    vector<float> label(number_of_images);

    cout << number_of_images << endl;

    for (int i = 0; i < number_of_images; i++) {
        unsigned char temp = 0;
        ifs.read((char*) &temp, sizeof(temp));
        label[i] = (float) temp;
    }
    return label;
}