src/mnist.c

src/mnist.c

@@ -0,0 +1,130 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <stdint.h>
+#include <inttypes.h>
+
+
+uint32_t swap_endian(uint32_t val) {
+    val = ((val << 8) & 0xFF00FF00) | ((val >> 8) & 0xFF00FF);
+    return (val << 16) | (val >> 16);
+}
+
+
+// Renvoie une image sous forme d'un int**
+int** read_image(unsigned int width, unsigned int height, FILE* ptr) {
+    unsigned char buffer[width*height];
+    int** image = (int**)malloc(sizeof(int*)*height);
+    
+    size_t ligne_size = sizeof(int) * width;
+
+    fread(buffer, sizeof(buffer), 1, ptr);
+
+    for (int i=0; i<height; i++) {
+        int* ligne = (int*)malloc(ligne_size);
+        for (int j=0; j<width; j++) {
+            ligne[j] = (int)buffer[j+i*width];
+        }
+        image[i] = ligne;
+    }
+    return image;
+}
+
+// renvoie [nb_elem, width, height]
+int* read_mnist_images_parameters(char* filename) {
+    int* tab = malloc(sizeof(int)*3);
+    FILE *ptr;
+    
+    ptr = fopen(filename, "rb");
+
+    uint32_t magic_number;
+    uint32_t number_of_images;
+    unsigned int height;
+    unsigned int width;
+
+    fread(&magic_number, sizeof(uint32_t), 1, ptr);
+    magic_number = swap_endian(magic_number);
+
+    if (magic_number != 2051) {
+        printf("Incorrect magic number !\n");
+        exit(1);
+    }
+
+    fread(&number_of_images, sizeof(uint32_t), 1, ptr);
+    tab[0] = swap_endian(number_of_images);
+
+    fread(&height, sizeof(unsigned int), 1, ptr);
+    tab[1] = swap_endian(height);
+
+    fread(&width, sizeof(unsigned int), 1, ptr);
+    tab[2] = swap_endian(width);
+
+    return tab;
+}
+
+
+// Lit un set de données images sous format de la base de données MNIST
+int*** read_mnist_images(char* filename) {
+    FILE *ptr;
+    
+    ptr = fopen(filename, "rb");
+
+    uint32_t magic_number;
+    uint32_t number_of_images;
+    unsigned int height;
+    unsigned int width;
+
+    fread(&magic_number, sizeof(uint32_t), 1, ptr);
+    magic_number = swap_endian(magic_number);
+
+    if (magic_number != 2051) {
+        printf("Incorrect magic number !\n");
+        exit(1);
+    }
+
+    fread(&number_of_images, sizeof(uint32_t), 1, ptr);
+    number_of_images = swap_endian(number_of_images);
+
+    fread(&height, sizeof(unsigned int), 1, ptr);
+    height = swap_endian(height);
+
+    fread(&width, sizeof(unsigned int), 1, ptr);
+    width = swap_endian(width);
+
+    int*** tab = (int***)malloc(sizeof(int**)*width*height);
+
+    for (int i=0; i < number_of_images; i++) {
+        tab[i] = read_image(width, height, ptr);
+    }
+    return tab;
+}
+
+// Renvoie des labels formattés sous le format de la base MNIST
+unsigned int* read_mnist_labels(char* filename) {
+    FILE* ptr;
+
+    ptr = fopen(filename, "rb");
+
+    uint32_t magic_number;
+    uint32_t number_of_items;
+
+    fread(&magic_number, sizeof(uint32_t), 1, ptr);
+    magic_number = swap_endian(magic_number);
+
+    if (magic_number != 2049) {
+        printf("Incorrect magic number !\n");
+        exit(1);
+    }
+
+    fread(&number_of_items, sizeof(uint32_t), 1, ptr);
+    number_of_items = swap_endian(number_of_items);
+
+    unsigned char buffer[number_of_items];
+    fread(buffer, sizeof(unsigned char), number_of_items, ptr);
+
+    unsigned int* labels = malloc(sizeof(unsigned int)*number_of_items);
+
+    for (int i=0; i< number_of_items; i++) {
+        labels[i] = (unsigned int)buffer[i];
+    }
+    return labels;
+}